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Laboratoire National desChamps Magnétiques Pulsés

Annual Report 2007

L N C M P UMR 5147 CNRS-INSA-UPS143 Avenue de Rangueil – 31400 Toulouse– FranceWeb: http://www.lncmp.org

Cover: Quantum oscillation in the field induced normal state of underdoped YBa2Cu3Oy

(image courtesy of CIFAR)

Doiron-Leyraud Nicolas, Cyril Proust, David LeBoeuf, Julien Levallois, Jean-BaptisteBonnemaison, Ruixing Liang, D. A. Bonn, W. N. Hardy & Louis Taillefer."Quantum oscillations and the Fermi surface in an underdoped high-Tc superconductor".Nature 447,565 (2007)

LeBoeuf David, Nicolas Doiron-Leyraud, Julien Levallois, R. Daou, J.-B. Bonnemaison, N.E. Hussey, L. Balicas, B. J. Ramshaw, Ruixing Liang, D. A. Bonn, W. N. Hardy, S. Adachi,Cyril Proust & Louis Taillefer."Electron pockets in the Fermi surface of hole-doped high-Tc superconductors".Nature 450, 533 (2007)

Bangura A.F, J. D. Fletcher, A. Carrington, J. Levallois, M. Nardone, B. Vignolle, P. J.Heard, N. Doiron-Leyraud, D. LeBoeuf, L. Taillefer, S. Adachi, C. Proust & N. E. Hussey.“Small Fermi surface pockets in underdoped high temperature superconductors: Observationof Shubnikov-de Haas oscillations in YBa2Cu4O8.”Physical Review Letters, accepted for publication

Annual report LNCMP 2007

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Introduction

Dear reader,

you have before you the 2007 annual report of the Laboratoire National des Champs MagnétiquesPulsés, a mixed research unit of the Centre National de la Recherche Scientifique, the Institut Nationaldes Sciences Appliqués in Toulouse, and the University Paul Sabatier in Toulouse.

2007 has been a very productive years for us, in terms of science and magnet technology;- Several results obtained by LNCMP members were published in high impact journals and receivedcoverage from the press.- The in-house magnet development has produced several new magnet types that will find theirapplication in future experiments, amongst which a super-rapid cooling model.- We have almost completed the construction of a single turn installation,- The in-house scientific activities are continuously increasing in volume and impact and continue toattract new external users to the LNCMP installations.In addition to all this, the groundwork for several new scientific and technological developments waslaid, and we are therefore looking forward to an even more successful year 2008.

Geert Rikken, director LNCMP Toulouse, January 14th 2008

Table of contentsPage

ScienceHigh Tc superconductors 2Organic conductors 5Magnetism 9Nanophysics 15Magneto-optics 21Semiconductors 26Biophysics 32X ray scattering 34

InstrumentationDevelopment of high-strength conductors 39Magnets 43Generators 46Single turn installation 48

MiscellaneousUser facility activities 50Publications 58Organisation 66


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High Tc superconductors

Personnel involved:

Permanent:, C. Proust, D. Vignolles, A. Audouard, M. Nardone

Non permanent: J. Levallois (PhD), C. Jaudet (PhD), B. Vignolle (Postdoc), A. Zitouni

Collaboration: L. Taillefer (Université de Sherbrooke, Canada)N. Hussey (University of Bristol, UK)D. Bonn (University of British-Columbia, Canada)

Quantum oscillations and Hall effect in underdoped YBa2Cu3Oy

A useful way to characterize the electronic properties of a metal is to map out its Fermisurface (FS). It can be done be by measuring quantum oscillations in high magnetic field, either of themagnetoresistance (Shubnikov-de Haas –SdH- effect), or of the magnetization (de Haas-van Alphen –dHvA- effect) [1] but also with AMRO (angular dependence of the magnetoresistance) and ARPES(angle resolved photoemission spectroscopy).

In most metals, predictions of band structure calculations (LDA) are in good agreement withexperimental measurements. This is also the case in the overdoped side of the phase diagram of hightemperature superconductors (HTS), where it has been predicted and confirmed experimentally byAMRO [2], and ARPES [3] that the FS consists of a large cylinder covering 63% of the first Brillouinzone for a doping p = 0.25. By contrast, the underdoped regime is highly anomalous and appears tohave no coherent Fermi surface, but only disconnected ‘Fermi arcs’ [4] (yellow part of the sketch ofthe FS shown in the inset of Fig. 1), whose origin would be in the high orbit predicted by the LDAcalculations, with a pseudogap opening around (0, ) et (, 0).

Fig. 1 : Hall resistance as a function of magnetic field B for YBa2Cu3O6.5, at different temperaturesbetween 1.5 and 4.2 K [5]. The inset shows a sketch of the Fermi surface of HTS (from [6]).

Thanks to the synthesis of high quality single crystals by the group of D. Bonn and theimprovement in the signal/noise ratio measurement under pulsed magnetic field, we have observedquantum oscillations of the Hall resistance of the oxygen-ordered copper oxide YBa2Cu3O6.5 [5]. Witha Tc of 57.5 K, these samples have a hole doping per planar copper atom of p=0.10, that is, they are


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well into the underdoped region of the phase diagram. Fig. 1 shows the magnetic field dependence ofthe Hall resistance at different temperatures between 1.5 K and 4.2K. Beyond the superconductingtransition, clear oscillations of the resistance are observed. Quantum oscillations are a direct measureof the Fermi surface area via the Onsager relation: F=(0/2

2)Ak, where 0 is the flux quantum, andAk is the cross-sectional area of the Fermi surface normal to the applied field. A frequency of 530 Timplies a Fermi surface pocket that encloses a k-space area which represents only 1.9% of theBrillouin zone. The low oscillation frequency reveals a Fermi surface made of small pockets, incontrast to the large cylinder characteristic of the overdoped regime. It is worth noting that quantumoscillations tell us neither the number of pockets, nor their location in the reciprocal space. Although asmall pocket might appear in the LDA calculations for the specific doping ortho II, this is not the caseof the stoechiometric compound YBa2Cu4O8 [7], in which we have also observed quantum oscillationswith a similar frequency [8]. The later results therefore imply that these small pockets are a genericfeature of the copper oxide plane in underdoped cuprates. The comparison with the disconnected arcsseen by ARPES (assuming that only part of the pocket is detected) led us to first suggest a four nodalpockets scenario centred at (/ 2, /2), as shown in blue in the inset of Fig. 1.

Fig. 2 : Field dependence of the oscillatory part of the torque at different temperatures in YBa2Cu3O6.5.Solid lines are best fit to the Lifshitz-Kosevich formula (from [9]).

More recently, we have observed de Haas-van Alphen oscillations in the underdoped cuprateYBa2Cu3O6.5 [9] at very low temperatures in magnetic fields up to 59 T, using a piezoresistivecantilever. Fig. 2 displays the oscillatory torque versus 1/B between T = 5.2 K and T = 0.4 K.Oscillations can be observed down to Birr, in particular in the resistive superconducting transition.Black solid lines in Fig.2 are best fits to the Lifshitz-Kosevich formula, which describes the dHvAoscillations for a 2D Fermi liquid. The deduced oscillation frequency is F = 5404 T, in excellentagreement wit the SdH measurements. This thermodynamic observation of quantum oscillationsconfirms the existence of a well-defined, close and coherent, Fermi surface in the pseudogap phase ofcuprates.

A four nodal (hole) pocket scenario for the FS of underdoped YBCO can not explain thenegative sign of the Hall effect (see Fig. 3) observed at three different doping [10] and the apparentviolation of the Luttinger sum rule, which states that the total carrier density n must be equal to thetotal area of the two-dimensional Fermi surface (from the oscillation frequency F=530 T, one gets acarrier density nSdH=0.038 carriers per planar Cu atom per pocket, that is to say a total carrier densityof ~15% in a four nodal pocket scenario, instead of 10% given by the doping). The most naturalexplanation for the negative Hall effect is the presence of an electron pocket in the Fermi surface. In a


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scenario in which the Fermi surface contains both electron and hole pockets, the sign of the Hall effectdepends on the relative magnitude of the respective densities ne and nh, and mobilities e and h. Thefact that the Hall effect is negative at low T therefore implies that e > h at low T and that the SdHfrequency must come from the high-mobility electron pocket, because the amplitude of SdHoscillations depends exponentially on mobility, as exp(–/B). Moreover, if the Fermi surfacecontains other sheets (not seen in the Shubnikov–de Haas oscillations) besides the observed pockets,then the Luttinger sum rule can easily be satisfied.

Fig. 3 : Hall coefficient RH versus T forYBa2Cu3O6.5 at different magnetic fields (from [10]). The insetshows the FS obtained after a (, ) reconstruction of the LDA FS.

A fundamental question is: how do electron pockets come to exist? The combination of asmall Fermi surface volume from SdH oscillations and a negative Hall effect pointing to electronpockets, argues strongly for a reconstruction of the LDA Fermi surface. One possible scenario is anantiferromagnetic phase with a (, ) ordering wavevector, which causes the large hole-like Fermisurface to reconstruct into a small hole pocket (blue in the inset of Fig. 3) at (/2, /2) and a smallelectron pocket (yellow) at (, 0). However, no such static order has been detected in YBCO but onlyfluctuations around the wave vector (, ), so further investigation into possible mechanisms for Fermisurface reconstruction is needed.

[1] D. Shoenberg, Magnetic Oscillations in Metals (Cambridge Univ. Press, Cambridge, 1984).[2] N.E. Hussey et al, Nature 425, 814–817 (2003).[3] M. Platé et al, Phys. Rev. Lett. 95 , 077001 (2005).[4] M. Norman et al, Nature 392, 157–160 (1998).[5] N. Doiron-Leyraud et al, Nature 447, 565 (2007).[6] S.R. Julian and M.R. Norman, Nature 447, 537 (2007).[7] A. Carrington and E.A. Yelland, Phys. Rev. B 76, 140508 (2007).[8] A. Bangura et al, accepted for publication in Phys. Rev. Lett (arXiv:0707.4461).[9] C. Jaudet et al, arXiv: 0711.3559[10] D. Leboeuf et al, Nature 450, 533 (2007).


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Organic conductors

Personnel involved:

Permanent: Alain Audouard, M. Nardone, David Vignolles

Collaborations: R. Lyubovskaia, R. Lyubovskii, E. Yagubskii (IPCP, Chernogolovka); J.-Y. Fortin(LPT Strasbourg); E. Canadell, V. N. Laukhin, (ICMAB, Barcelona ). Supported by CNRS-CSICexchange program (project 16210).

Frequency combinations in coupled orbits networksAccording to band structure calculations, the Fermi surface (FS) of many quasi-two-

dimensional (q-2D) organic metals with two charge carriers per unit cell originates from one hole tubewhose area is therefore equal to that of the first Brillouin zone (FBZ) area. This tube can go over theFBZ along either one or two directions leading to FS with different topologies. Due to gap opening atthe crossing points, the resulting FS is composed of a q-2D tube and a pair of q-1D sheets in theformer case while, in the second case, compensated electron and hole tubes are observed. In highenough magnetic field, both of these FS can be regarded as networks of orbits coupled by magneticbreakthrough (MB) which can therefore be classified according to two types: (i) the well known linearchain of coupled orbits introduced by Pippard in the early 1960's and (ii) the network of compensatedelectron-hole orbits, respectively. Type (ii) networks can also be obtained in organic metals whose FSoriginates from two (or more) pairs of crossing q-1D sheets. In all cases, oscillatory magnetoresistancespectra exhibit Fourier components at frequencies which are linear combinations of few basicfrequencies.

In type (i) networks (see the inset of Fig. 1), many combinations that can be attributed to MB(β+ α, β+ 2α, etc.) are observed in the Fourier spectra, in addition to frequencies linked to the q-2D αorbit and to the MB-induced βorbit (which corresponds to the hole tube from which the FS is built),other Fourier components such as β- αor β- 2αare also detected. These latter frequencies areinterpreted on the basis of quantum interference (QI), although they are also observed in de Haas-vanAlphen (dHvA) oscillations spectra.

According to theoretical studies, both the field-dependent modulation of the density of statesdue to MB and the oscillation of the chemical potential can also induce frequency combinations inmagnetoresistance and dHvA oscillatory spectra. Nevertheless, the respective influence of each ofthese contributions to the magnetoresistance and dHvA spectra remains to be determined. Amongthese, the oscillation of the chemical potential can be strongly reduced at high temperature and forhigh scattering rate. Nevertheless, small effective masses are required in this case in order to observequantum oscillations with a high enough signal-to-noise ratio, in a large field range.

Fig. 1: Magnetoresistance, corresponding Fourieranalyses and Fermi surface of the organic metal(BEDO-TTF)5Ni(CN)4 ·3C2H4(OH)2.


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Fig. 2: Oscillatory magnetoresistance of a dirty(BEDO-TTF)5Ni(CN)4 ·3C2H4(OH)2 crystal.Quantum oscillations are clearly observed at cvalues much below than 1

This is the case of the organic metal (BEDO)5Ni(CN)4·3C2H4(OH)2, of which the oscillatorymagnetoresistance spectra has been studied up to 50 T (see Fig. 1). The temperature and fielddependence of the Fourier components' amplitude linked to the closed αand to the MB-induced βorbits, analyzed in the framework of the semi classical model of Falicov and Stachowiak yieldconsistent results. The deduced scattering rate τD

-1 ≈6.1012 s-1 is very large which allows forconsidering that the contribution of the chemical potential oscillation to the oscillatorymagnetoresistance spectra is negligible in the explored field and temperature ranges. Despite of thisfeature, the recorded spectra exhibit many frequency combinations. Their effective mass and (or)Dingle temperature are not in agreement with either the predictions of the QI model or the semiclassical model of Falicov and Stachowiak. It can also be remarked that their amplitude can be verylarge. In particular, the amplitude of the components β- αand β+ αis larger than that of β(this latterfeature being not due to spin-zero phenomenon). These results suggest that the contribution of thecoherent MB-induced modulation of the density of states can play a significant role in the observedoscillatory behaviour. In contrast, both the temperature and the field dependencies of the componentlinked to the 2nd harmonics of αare in good agreement with the semi classical model (same Dingletemperature as for αand twice as large effective mass). The influence of the scattering rate wasstudied in a dirty crystal for which τD as low as ~ 0.1 ps is deduced from oscillatory data relevant tothe αorbit. Strikingly, quantum oscillations are clearly observed at cvalues much lower than 1 (seeFig. 2). This result evidences that questions remain to solve about (i) the determination of τfromquantum oscillations, even in the case where consistent data are deduced for basic orbits, as abovereported, and (ii) the nature of defects that govern this parameter in organic metals.

Electronic properties of organic superconductors containing magnetic ions

The family of q-2D organic metals ''-(BEDT-TTF)4(A)[M(C2O4)3].Solv, where A is amonovalent cation, M a trivalent cation and Solv is a solvent molecule, was made famous about tenyears ago by the discovery of a superconducting ground state at ambient pressure (Tc = 8.5 K) in thecompound with A = H3O+, M = Fe3+ and Solv = benzonitrile (which therefore contains magnetic ions)[Graham et al., J. Chem. Soc., Chem. Commun. (1995)]. Even though, all the members of this familyare isostructural, they exhibit very different ground states and behaviours as the temperature varies. Itis thus of primary importance to discover the eventual link between the electronic (and atomic)structure and the nature of the ground state.

We have measured the interlayer magnetoresistance of ''-(BEDT-TTF)4 (NH4)[M(C2O4)3]·DMF(M = Fe, Cr) up to 55 teslas under pressures of up to 1 GPa (see an example in Fig 3).


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Fig. 3: Magnetoresistance at 2K for various applied pressures (a), corresponding Fourier analyses (b) andpressure dependence of the frequencies (c) of the organic metal ''-(BEDT-TTF)4(NH4)[Fe(C2O4)3]·DMF.

In agreement with band structure calculations, the Shubnikov-de Haas (SdH) oscillations spectraof the compound with M = Fe can be interpreted on the basis of three compensated orbits in all thepressure range studied, suggesting that the FS topology remains qualitatively the same as the appliedpressure varies. These orbits are labelled a, b – a, and b in Fig. 3 (the Fourier components labelled a +b and 2b are likely due to frequency combinations, see above). In addition, all the observedfrequencies, normalized to their value at ambient pressure, exhibit the same pressure dependence.Despite this behaviour, which is at variance with that of numerous charge transfer salts based on theBEDT-TTF molecule, non-monotonous pressure-induced variations of parameters such as theeffective mass and the scattering rate linked to the various detected orbits are observed. In addition,the pressure sensitivity of the frequencies is extremely large since an increase of 45% is observed at 1GPa. These features suggest that the applied pressure induces a strong deformation of the FS eventhough it remains qualitatively similar in the studied range.

In contrast with the above discussed compound, the FS of the organic metal with M = Cr is rathercomplex at ambient pressure since up to 6 fundamental frequencies are observed. However, itsoscillatory spectrum drastically simplifies under pressure. Indeed, above 0.8 GPa, its FS can beaccounted for by 3 compensated electron and hole orbits only, as it is the case of the M = Fecompound in the whole explored pressure range.

The field-dependent resistance of ''-(BEDT-TTF)4(H3O)[Fe(C2O4)3]·dichlorobenzene have beenmeasured up to 53 T. The oscillatory data are consistent with a FS composed of 3 compensated orbits,as in the case of the Fe compound mentioned above. Even though, as expected, the scattering rate issignificantly lower than for the above mentioned compounds (D

-1 ~ 2.5x1012 s -1), almost no frequencymixing is observed. Nevertheless, the most salient feature regarding this compound is the kinkobserved in the temperature dependence of the SdH oscillations’ amplitude: the correspondingeffective mass is mc ~ 1.35 and mc ~ 0.35 at low and high temperature, respectively. As a result, SdHoscillations can be detected at temperatures even higher than 30 K, although in the high magnetic fieldrange, only (see Fig. 4).

Fig. 4: Temperature dependence of theoscillations amplitude (upper panel),oscillatory magnetoresistance at low andhigh temperature and Fourier analysis of ''-(BEDT-TTF)4(H3O)Fe(C2O4)3]· dichloroben-zene. .SdH oscillatiosn are clearly observedat 32 K.


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In order to elucidate this behaviour, which could be due to e. g. either a coexistence of twooscillatory phenomena with the same frequency in the whole temperature range or to some phasetransition, torque measurements are planned up to 55 T. The aim of this experiment is two-fold.Indeed, as a thermodynamic parameter, magnetization is liable to present some signature of aneventual phase transition. In addition, the study of dHvA oscillations could give important information.Indeed, an effective mass as low as that observed in the high temperature range is generally attributedto quantum interference. In the case where this hypothesis is correct, dHvA oscillations which are onlysensitive to the density of states should not reveal any change of effective mass. Alternatively, in thecase where a temperature-induced modification of the FS actually occurs, a variation of the effectivemass should be observed both for SdH and dHvA oscillations.

In summary, all these results demonstrate the extreme sensitivity of the electronic structure tosubtle changes of the atomic structure and confirm that we are still far from clearly understand thesubtle details responsible for the electronic structure of this remarkable family of organic compounds.

Further developments:

We are going to study the relationship between the topology of the FS (corrugation and MB gaps)tuned by hydrostatic pressures of up to 1 GPa both in the above discussed type (i) network and in theorganic metals (BEDT-TTF)8Hg4Cl12(C6H5X)2 (X = Br, Cl) that correspond to type (ii). In addition, atheoretical calculation of the free energy in type (ii) networks, which allow for the determination ofthe dHvA effect, is under way (coll. J. Y. Fortin). This latter study is expected to give a reliable toolfor the analysis of the oscillatory spectra of clean compensated organic metals.


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Magnetism

Personnel involved:

Permanent: M. Goiran, B. Raquet, W. Escoffier, H. Rakoto, J.M. Broto

Non permanent: M. Millot, S. Nanot

Collaboration: detailed in each topic

Strong electron-phonon coupling in the rare-earth carbide superconductor La2C3

Collaborations :Kim, J. S., Xie, Wenhui, Kremer, R. K., Babizhetskyy, V., Jepsen, O., Simon A. :MPI fur Festkorperforschung Stuttgart Germany ; K.S. Ahn, : Department of Chemistry YoseiUniversity Wonju, South Korea ; Ouladdiaf, B.ILL Grenoble

PRB 76 (1): Art. No. 014516 JUL 2007

We have determined the crystal structure using neutron powder diffraction as well as thesuperconducting properties of the rare-earth sesquicarbide La2C3 (Tc approximately 13.4 K) by meansof specific-heat and upper critical field measurements. From the detailed analysis of the specific heatand a comparison with ab initio electronic structure calculations, a quantitative estimate of theelectron-phonon coupling strength and the logarithmic average phonon frequency is made. Theelectron-phonon coupling constant is determined to be ph 1.35. The electron-phonon coupling tolow energy phonon modes is found to be the leading mechanism for superconductivity. Our resultssuggest that La2C3 is in the strong-coupling regime, and the relevant phonon modes are La relatedrather than C-C stretching modes. The upper critical field shows a clear enhancement with respect tothe Werthamer-Helfand-Hohenberg prediction, consistent with the strong electron-phonon coupling.


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High field magnetisation measurements on UIr in the ferromagnetic state

Collaborations : Sakarya, S., van Dijk, Delft University of technology The Netherlands, de Visser, A.,Brueck, E., Huang, Y., University of Amsterdam, The Netherlands, Perenboom, J. A. A,.HFMLUniversity of Nijmegen, The Netherlands

JMMM 310 (2): 1564-1565 Part 2, MAR 2007

We have performed high field magnetisation measurements on the ferromagnetic order (TC = 46 K) insingle-crystalline UIr. The magnetisation along the easy axis shows a field saturation towards amoment of about 1 B/U atom at T = 4.2 K. No field-induced magnetic transition was observed formagnetic fields up to 52T.

Helimagnetism and weak ferromagnetism in edge-shared chain cuprates

Collaborations : Drechsler S-L., Buchner, B, Tristan, N: Leibniz Institute for Solid State and MaterialsResearch IFW Dresden, Germany ; Richter J.: Institut fur Theoretische Physik UniversitatMagderburg Germany ; Kuzian, R : Institute for Problems of Materials Science, Kiev, Ukraine ;Malek, J.: Institute of Physics, ASCR, Prague, Czech Republic ; Moskvin, A. S.: Ural StateUniversity Ekaterin burg, Russia ; Gippius, A. A., Vasiliev, A., Volkova, O.: Moscow StateUniversity Moscow, Russia ; Prokofiev, A.: Institut fur Festkorperphysik Technische UniversitatWien, Austria ; Schnelle, W., Schmitt, M., Ormeci, A., Loison, C., Rosner, H : MPI fur ChemischePhysik fester Stoffe, Dresden, Germany.

JMMM 316 (2): 306-312 SEP 2007


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We reviewed the understanding of a novel growing class of chain cuprates with intriguing magneticproperties Among them, several undoped edge-shared CuO2 chain compounds show at lowtemperature a clear tendency to helicoidal magnetical ordering with acute pitch angles and sometimesalso to weak ferromagnetism. Our analysis is based on the isotropic 1D frustrated J(1)-J(2) Heisenbergmodel with ferromagnetic (FM) 1st neighbour and antiferromagnetic 2nd neighbour exchange. Theachieved assignment is supported by microscopic calculations of the electronic and magnetic structure.We consider Na(Li)Cu2O2, LiVCuO4 as the best studied helimagnets, Li2ZrCuO4 and other systemsclose to a FM quantum critical point, as well as Li2CuO2 with FM in-chain ordering. We discussed theinterplay of frustrated in-chain couplings, anisotropy and inter-chain exchange.


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High field magnetization of the frustrated one-dimensional quantum antiferromagnet LiCuVO4

Collaborations : Banks, M. G., Kremer, R. K. : MPI fur Festkorperforschung Stuttgart Germany ;Heidrich-Meisner F.: Materials Science and Technology Division Oak Ridge National Laboratory,USA ; Honecker A. : Institut fur Theoretische Physik, Universitat Gottingen Germany.

J OF PHYS-COND MAT 19 (14): Art. No. 145227 APR 11 2007

We have investigated the high field magnetization of the frustrated one-dimensional compoundLiCuVO4. In zero field, LiCuVO4 undergoes long range antiferromagnetic order at TN approximately2.5 K with a broad short range Schottky type anomaly due to one- dimensional correlations in thespecific heat at 32 K. Application of a magnetic field induces a rich phase diagram. An anomaly in thederivative of the magnetization with respect to the applied magnetic field is seen around 7.5 T with Hparallel to c in the long range order phase. We investigated this in terms of a first experimentalevidence of a middle field cusp singularity (MFCS). Our numerical density matrix renormalizationgroup results show that in the parameter range of LiCuVO4 as deduced by inelastic neutron scattering(INS), there exists no MFCS. The anomaly in the derivative of the magnetization around 7.5 T istherefore assigned to a change in the spin structure from the ab plane helix seen in zero field neutrondiffraction.

Magnetic properties of the semimagnetic semiconductor Zn0.15Mn0.85Ga2Se4

Collaborations : Cadenas, R., Perez, Flor V., Quintero, M., Quintero, E., Tovar, R., Morocoima, M.,Gonzalez, J., Bocaranda, P., Ruiz, J., Centro de Estudios de los semiconductors Universidad de losAndes Merida , Venezuela

PHYSICA B-COND MAT 389 (2): 302-305 FEB 15 2007

We have studied the magnetic properties of the semimagnetic semiconductor Zn0.15Mn0.85Ga2Se4

(ZMGSe). The DC susceptibility and high magnetic field indicate that the ZMGSe ordersantiferromagnetically at T 6 K and goes into a spin-flop phase below this temperature. Arrott plotsand magnetic entropy changes were used to characterize the order of the transitions.


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The low dimensional spin magnet CaCu2O3 probed by high field ESR.

Collaborations : V. Kataev, U. Schaufus, R. Klingeler, C. Sekar, G. Krabes, N. Tristan, A. Waske, C.Hes, S.-L. Drechsler, B. Buchner: Leibniz Institute for Solid State and Materials Research IFWDresden, Germany

JMMM 310 (2007) 1251-1253

Magnetization and high field electron spin resonance response of the s = 1/2 Heisenberg pseudo –ladder magnet CaCu2O3 is dominated at low temperatures by a few percent of “extra” Cu spin statesarising due to the structural disorder. These “extra” spins interact with the bulk spins and jointly orderantiferromagnetically at TN = 26K. At T< TN ESR data reveal a small magnon anisotropy gap of theorder of 1 meV. Substitution of 15 % of nonmagnetic Zn for Cu reduces the concentration of“extra” spins and results in the suppression of the magnetic order and closing the magnon gap. Theseresults support the scenario with a significant role of the “extra” spins for stabilization of the magneticorder in this frustrated quantum magnet.


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Microwave absorption in the singlet paramagnet HoVO4 in pulsed magnetic fields up to 40 T.

Collaborations : R. Klingeler, , V.V. Snegirev Leibniz Institute for Solid State and Materials ResearchIFW Dresden, Germany ; Z.A. Kazei Physics department, Moscow State University, Russia.

JMMM, 318, (2007)1-7

Microwave absorption of the rare earth oxide compound HoVO4 (tetragonal –zircon structure) wereinvestigated in pulsed fields up to 40T in the low temperature range. For a magnetic field along thetetragonal crystal axis a few resonance absorption lines are observed at the wavelengths 871, 406 and305 m corresponding to electron transitions from the ground and low- lying energy levels of the Ho3+

ion. In addition, broad non-resonance absorption is observed at 871 and 406 m in fields up to 15T.The positions and intensities of the observed resonance lines are described quite well within the crystalfield formalism with the known crystal field parameters. The effects of the small orthorhombiccomponent of the crystal field, magnetic field misorientation out the symmetry axis and various pairinteraction on the absorption spectra in HoVO4 have been analyzed.


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Nanophysics

Personnel involved:

Permanent : J-M Broto, W. Escoffier, M. Goiran, V.Krstic, O. Portugall, B. Raquet, G.RikkenPost doctorate: Stefan HanselPh D Students: M. Millot, S. Nanot, N. UbrigCollaborators: J. Gonzalez (Merida-Venezuela), E. Flahaut (CIRIMAT- Tlse), M. Monthioux & Th.Ondarçuhu (CEMES – Tlse), Ch. Vieu ( LAAS), B. Lassagne (ICN), L. Forro (EPFL), S. Roche(CEA), K. Novoselov (Univ Manchester), J Blokland, (HFML - Nijmegen), S. Roth (MPI - Stuttgart),J. Kono & J. Shaver (Rice University, Houston), P. Plochocka, M. Potemski, G. Martinez (GHMFL,Grenoble)._________________________________________________________________________________________

The LNCMP activities in nanophysics are focused on magneto-transport and magneto-opticalproperties of carbon nanotubes and graphene.___________________________________________________________________________

Magneto-transport and Landau quantization in individual ballistic carbon nanotubesLNCMP : J-M Broto, W. Escoffier, S. Nanot, B. RaquetCollaborations: S. Roche (CEA), E. Flahaut (CIRIMAT- Tlse), M. Monthioux & Th. Ondarçuhu(CEMES – Tlse), Ch. Vieu (LAAS), L. Forro (EPFL), B. Lassagne (ICN)

As in the case of graphene, the remarkable electronic properties of carbon nanotubes lie in theirparticular energy dispersion relation. Nevertheless, depending on the topological structure (or chiralindices), carbon nanotubes are either metallic or semi-conducting quasi-one dimensional systems.Their cylindrical geometry makes them very sensitive to the application of an external magnetic fieldand to its direction with respect to the nanotube axis. Recently, unprecedented mesoscopic effects havealready been reported in the configuration where the magnetic field is oriented parallel to the carbonnanotube axis: Aharonov-Bohm conductance modulation and quantum interference beating in theballistic regime have unveiled the magnetic field dependence of the transverse allowed-kperp vectors[1]. However, little is known in the other configuration, where the applied magnetic field isperpendicular to the carbon nanotube axis. In this case, an analogy with the graphene's magnetic bandstructure is tempting since carbon nanotube and graphene have in common their low-energy masslesselectronic dispersion at the K and K' points of the Fermi surface. Nevertheless, the situation is fairlymore complex as, at first sight, the normal projection of the magnetic field vector onto the tube's wallhas a periodic dependence along its circumference.We report on transverse magneto-conductance experiments performed on individual multi-wall carbonnanotubes (MWCNT) in the high magnetic field regime, > 1 [2]. Samples that displaysemiconducting behavior show spectacular change of the conductance under 55T (which sign is back-gate voltage dependant -Fig.1). We assign this unconventional magneto-conductance to as a firstevidence of the onset of the magnetic band structure. Moreover, under very high magnetic field (>1),the conductance develops a unique value over a large electrostatic doping range. A tentativeexplanation of this observation is described in terms of propagating states at the flanks of the tube,within the first Landau level.On the other hand, metallic quasi-ballistic MWCNTs develop Fabry-Perot like interference pattern atlow temperature, in the vicinity of the charge neutrality point . A large magnetic field appliedperpendicular to the tube drastically modifies the electronic resonances of the cavity (Fig.2). Ouranalysis unveils the magnetic field dependence of the resonant k// vectors due to the flattening of themetallic bands at the CNP. Our measurements are favorably compared to the first simulation of theFabry-Perot modulation under magnetic field, based on the Landauer conductance formalism.[1] B. Lassagne & al, Phys. Rev. Lett. 98 (17), 176802 (2007)[2] S. Nanot & al, in preparation.


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0 10 20 30 40 50 60

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)

B(T)

10V

8V

6V

5V

4V

3V

2V

G(2

e²/h

)

Vg (V)

CNP

Fig.1: Magneto-conductance versus a back gatevoltage, under a perpendicular magnetic field,obtained at 150K on a semiconducting MWCNT. Thedot line represents the expected closing of the energygap under perpendicular field. In inset, the G(Vg)curve indicating the charge neutrality point and theexpected location of the sub-bands.

0 10 20 30 40

0,6

0,8

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e2/h

)

B(T)

B(T)

(a)

G(2

e2/h

)

Fig.2: Magneto-conductance versusdifferent back gate voltages, under aperpendicular magnetic field, obtained at4K on a metallic MWCNT in the Fabry-Perot regime. The gate voltage variesfrom a resonant state to an off-resonantstate at B =0.

Raman-gate on individual MWCNTs

LNCMP : M. Millot, J-M Broto, X. Escoffier, S. Nanot, B. RaquetCollaborations: Ch. Power, G. Belandria, J. Gonzalez (ULA – Venezuela)

Raman spectra of individual MWCNT have been investigated on samples connected in backgateconfiguration. These samples have shown a very low D-band characterizing a good crystalline quality.On the other hand, the G-band is modified under the application of a gate voltage (i.e. a shifting of theFermi level of the nanotube). The different spectra are a combination of three lorentzians resultingfrom the electron-phonon coupling within the three first shells, the position of the maxima is shiftingwith a minimum at the charge neutrality point. The variation of the half height maximum width isharder to follow but seems to show the same kind of evolution. This behaviour could be attributed theDirac nature of the electronic dispersion, the data are still under analysis.

Fig.1 : µ-Raman spectra of an individualMWCNT for different back-gate voltages

Fig.2 : Back-gate voltage effect on the µ-Ramanspectra resulting from the e-ph coupling within the

three first shell.


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On the investigation graphene and thin graphitic systems electronic properties

LNCMP : W. Escoffier, M. Goiran, B. Raquet, S. NanotCollaborations : K.S. Novoselov (University of Manchester – U.K.), C. Chapelier (CEA Grenoble –France)

Graphene is a newly discovered 2D electron gas [1], which electronic properties mimic the relativisticbehaviour of charge carriers [2] (also termed massless Dirac fermions) predicted by the Dirac equation.This particular effect was first revealed through the Quantum Hall Effect, which shows half-integerconductance quantization at half-integer filling factors [3]. This discovery triggered new research onvery thin graphitic systems, where reminiscences of graphene’s special electronic properties could beobserved [4]. At the charge neutrality point of the system, the charge carrier density is stronglyreduced leading to less effective screening [5]. Subsequent enhanced Coulomb interactions areexpected to strongly modify the usual Landau level framework needed to explain most of themagneto-resistance phenomena.

In practice, the use of very high magnetic fields are required for investigating the Quantum Hall Effectregime, where low filling factor (v<=1) could be reached. Very recently, preliminary magneto-transport measurements performed on thin graphitic systems provided by the University of Manchesterhave shown Landau level quantization effects which could be traced back even at high [6] temperature(250K). The detailed sequences of plateaus in the Hall resistance (Rxy) and associated oscillations inthe transverse 2-contacts resistance (Rxx) as function of magnetic field and back-gate voltage (shownbelow) are currently under investigation.

Figure 1 : 2-contactstransverse magneto-resistanceas a function of back-gatevoltage (Vg) and magneticfield (B). While the overallresistance behaviour is seen at250K, reproducible and back-gate dependant oscillationsare revealed at lowtemperature

Figure 1 : Hall resistanceas a function of back-gatevoltage (Vg) and magneticfield (B). Depending onback-gate voltage, resistanceplateaus at about 6kΩ and12kΩare clearly seen undervery high magnetic field.

[1] K.S. Novoselov & al. PNAS 102, 10451 (2005)[2] M.I. Katsnelson, MaterialsToday 10, 20 (2007)[3] Y. Zhang & al. Nature 438, 201 (2005) ; K.S. Novoselov & al. Nature 438, 197 (2005)[4] G. Li & al. Nature Physics ,1 (2007) ; M.L. Sadowski & al. Phys. Rev. Lett. 97, 266405 (2006)[5] E.H. Huang & al. Phys. Rev. Lett. 98, 186806 (2007)[6] K.S. Novoselov & al. Science-xpress (15/02/2007) page 1.


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First Measurement of Quantum Hall Effect on Graphene up to 55T

LNCMP: G. Rikken, V. Krstić, S. HanselCollaboration: J. Blokland (HFML Nijmegen), S. Roth (MPI für Festkörperforschung -Stuttgart)

We were measuring the 2-point resistance of monolayer graphene prepared by the “scotch” technique[K.S. Novoselov et al., Science 306 (2004), Nature 438 (2005)] on a n+-doped substrate with athermally grown SiO2-layer, to be used as a back gate. The graphene deposited on the substrate wasthen lithographically contacted. In the upper inset of the figure below, a clear maximum of 2-point-resistance could be found at ~+10V gate voltage, which is the Dirac-point.

As shown on the graph, we were able to observe plateaus in the two point resistance at lowtemperatures of about 5K at a gate voltage of +30V. In particular long, unconventional plateaus areseen (at about 15T). In the lower inset the two-point resistance of this graphene layer up to 8 T isshown where Hall-plateaus can be observed, too. This constitutes the first ever observation of quantumHall effect phenomena in graphene up to 55T. Similar results were obtained for this and other samplesdifferent at gate voltages, current magnitudes, field orientations and temperatures. The physical originof the long unconventional plateau is currently under discussion (V. Krstićet al., in preparation).

-2 0 2 4 6 8 10 12 14 16

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=30V

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sist

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]

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Infrared spectroscopy of DNA-wrapped carbon nanotubes.

LNCMP: O. Portugall, N. UbrigCollaboration: J. Kono, J. Shaver (Rice University, Houston)

In previous years we have investigated the absorption and photo-luminescence of liquid suspensionsas well as aligned films of carbon nanotubes. We have thus obtained clear evidence for the splitting ofabsorption lines induced by the Aharonov-Bohm phase and the magnetic brightening of the photo-luminescence that confirms the existence of a dark exciton ground state. In parallel, our measurementshave revealed information on the dynamic alignment of carbon nano-tubes in liquid suspension thathas not yet been consequently analysed and published.A major drawback of our previous results lies in their qualitative character: In pulsed magnetic fieldsoptical measurements on carbon nanotubes are inevitably restricted to large ensembles whosecollective response helps to avoid the extended integration times necessary for single-tubespectroscopy. The fact that such ensembles are composed of different types of tubes, however,introduces additional degrees of freedom that can make a detailed evaluation of experimental resultscumbersome.DNA-wrapped carbon nanotubes represent a major improvement in the latter respect, as the chiralityof the surfactant, i.e. DNA, enhances the solubility of specific tubes in the suspension that serves asbase material for preparing samples. We are currently studying samples of this type whose absorptionand photo-luminescence spectra exhibit a single dominant line thus confirming the presence of amajority of nanotubes with fixed chirality.We expect that these studies will enable us to obtain quantitative conclusions concerning thecomposition of electronic wave functions brought forth by a magnetic field (K or K') as opposed to theinherent Coulomb interaction (K-K' mixing).Our samples have also been rheologically analysed in order to enable us to shed more light on thealignment dynamics of carbon nanotubes in liquid solution.

Infrared spectroscopy of Graphene.

LNCMP: O. Portugall, N. UbrigCollaboration: P. Plochocka, M. Potemski, G. Martinez (GHMFL, Grenoble)

The application of high magnetic fields to study the optical properties of graphene is primarilymotivated by the search for a breakdown of the quasi-relativistic regime, which gives rise to chargecarriers featuring zero effective rest mass. Following infrared absorption measurements performed bySadowski et al and Plochocka et al applying magnetic fields up to 32 T at the GHMFL Grenoble wehave recently started experiments in pulsed magnetic fields up to 56 T. Our measurements haverevealed shifts of the main absorption lines that basically follow the characteristics already observed inGrenoble. However, in contrast to earlier measurements at lower field we have observed deviations inthe resonance lineshapes for left and right handed circular polarization that indicate an unexpectedasymmetry between electrons and holes. Further measurements to verify and study this effect arescheduled for the beginning of 2008.


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FIG. 1: (a) Representative differential trans-mission spectra (the B = 0 T spectra has been subtracted)measured at the given magnetic fields. (b) Positions of the absorption lines as a function of the squareroot of the magnetic field. Stars and tr iangles represent data obtained in near visible range (starsdenote the results got in a steady state, triangles in a pulsed magnetic field), circles denotes the datameasured by FTS. Dashed lines are calculated energy of the transitions between LLs assuming alinear dispersion. On the right hand side the observed transition L-m(-n) -> Ln(m) LLs are denoted.


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Magneto-optics

Personnel involved:

Permanent: R. Battesti , P. Frings, V. Krstic, JP. Laurent, M. Nardone, O. Portugall, G. RikkenNon-permanent: S. Batut, J. Mauchain, F. Bielsa, A. ZitouniCollaborations: B. Pinto da Souza, C. Robilliard, M. Fouché, C. Rizzo (LCAR, Toulouse).

Vacuum Magnetic Birefringence experiment (BMV).The BMV experiment [1] is now ready in its clean room at the LNCMP. 2007 was the second year ofthe program ‘ANR Blanc-BMV’. During this year we have changed a lot of mechanical components inour apparatus in order to reach a better sensitivity and a better vacuum. We have mounted a Fabry-Perot cavity of finesse 6000 on rotating mirrors under vacuum (photo 1).

Photo 1. Cavity mirror on its rotating mount

We have locked the frequency of our Nd-YAG laser on this cavity thanks to a novel locking schemedeveloped at LCAR. This servo loop is a key element in our apparatus because we combine highmagnetic fields (and thus perturbations) with a resonant Fabry Perot cavity of very high finesse; itworks very well (e.g. the servo loop allows us kicking the table without loosing resonances in thecavity). We have measured the power spectral density (PSD) of the transmitted intensity after thecavity. We reached a PSD of 5x10-6 Hz-1/2. Nevertheless we try to improve these limits by developinga phase locked loop which should control the phase noise induced by our optical fibre and shouldreduce the PSD after the cavity.

Furthermore, we have finished the installation of the vacuum components. Especially weplaced the vacuum tubes which passed through the cryostats and we placed a residual gas analyser forstudying the residual gases in the cavity.

Vacuum tubes

Figure 1- Scheme of the cavity setup, with both cryostats via which the vacuum tubes pass


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We have tested the vacuum by heating the chambers and after 2 days we reached a vacuum of 10-7

mbar..

Photo 2. Cavity set up with the heating wires.

In the mean time, we have wound and tested a second X-coil (identical to the first one [2]) with itscryostat. We tested the shielding of the magnetic field in order to minimize stray fields at the cavitymirrors. As a matter of fact, magnetic fields induce a Cotton Mouton effect in the layers of mirrors.This effect is really disturbing because it’s in phase with our signal. Then we must cancel stray fieldsnear the mirrors. Thanks to 2 cylindrical shields placed in the cryostat, we reduce stray fields by afactor 2. The residual field on mirrors is about 2x10-4 T what is reasonable for the moment. Both coilsare ready to be mounted in the experiment.

In the beginning of 2008, we should be ready to place the very high finesse mirrors in ourcavity. Then we hope to obtain a Fabry Perot cavity of finesse 300 000 on which the laser will belocked. In february-march 2008, we should place both coils on the experiment in order to begin thefirst measurements with the magnetic field combined with the locked cavity.

The photoregeneration experiment

The aim of this experiment was to confirm the possibly existence of a new particle called axion. Theaxion was first proposed 30 years ago as a new particle to solve a fundamental symmetry problem inelementary particle physics. The axion could be a major component of the dark matter [3] of whichour universe mainly consists, but it has so far eluded experimental observation. Since it is predicted tobe extremely weakly coupled to ordinary matter, such an observation is a very challenging task.

Last year, an italian collaboration (PVLAS) published a surprising report of the observation ofa small rotation of the polarization of light in vacuum by a strong transverse magnetic field. Theauthors explained their result through the disappearance of photons, converted by the magnetic fieldinto a new particle, possibly the axion [4]. They also announced the observation of a small reductionof the velocity of light, which they also explained in terms of axions. However, the value of thephoton-axion coupling inferred from the PVLAS results is inconsistent with astrophysical constraints.Clearly, one needs new theories to reconcile the PVLAS interpretation and astrophysical observations,and some have already been proposed [5]. The most convincing set-up for a purely laboratory-basedaxion search, free from model dependent assumptions, is "light shining through the wall" [6]. Such anexperiment is based on the Primakoff effect; an axion is created by photon conversion in a magneticfield, after which the axion can leave the magnetic field region while the light beam is blocked by awall. After the created axion has passed through this wall into another magnetic field region, it can beconverted back into a photon that can be easily detected. Several of these "shining wall" experimentsto test the PVLAS results have recently been proposed and are currently under construction [7] ; atDESY the Axion-Like Particle Search project (ALPS) ; at CERN, the Optical Search for QED vacuummagnetic birefringence, Axions and photon Regeneration project (OSQAR) ; at Jefferson Laboratory,the LIght PseudoScaler Search project (LIPSS) ; at Fermilab, the GammeV Particle SearchExperiment project. All have announced their first experimental results by the end of 2007. In themean time, the PVLAS collaboration has posted a preprint disclaiming their previous observations.


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The light retardation signal is still present at 5.5 T, while no such a signal is observed at 2.3 T [7]. Itwas evident that a new and independent laboratory test of the existence of dark matter generated bylight and magnetic field was urgently needed. We have been the first to perform such a test. Ourexperiment is a collaboration between three laboratories:

- LNCMP in Toulouse- Laboratoire Collisions Agrégats et Réactivité in Toulouse- Laboratoire pour l’Utilisation des Lasers Intenses in Palaiseau.In our experiment (fig 2), photons provided by one of the most energetic pulsed lasers in the

world (1 kJ per pulse) can be converted into axions in an intense pulsed magnetic field (B > 12 T)parallel to the photon polarization. If axions are created under these conditions, they will be convertedback to photons in a second identical magnet, placed behind a wall. Any regenerated photons arecounted by a time gated single photon detector.

Figure 2 - Experimental setup in the laser hall in LULI.

Our pulsed approach allows us to measure very small conversion rates free from the inevitablefalse counts of photon detectors. We have not detected any regenerated photons, testing conversionand back conversion on a total of more than 1023 incident photons, while at least a few should havebeen observed according to the PVLAS result. We can therefore invalidate the axion interpretation ofthe original PVLAS results, with a confidence level higher than 99% [7]. In the figure (3), we showthe new existence limits for the axion, resulting from our null result, in terms of the axion mass ma andthe inverse of the axion-photon coupling constant M. Additional measurements are now underway inorder to increase the exlusion region.


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Figure 3 –Our exclusion region. M is the inverse coupling constant of axion-like particles and ma theirmass. Our region is given by the red area.

References :

[1] : R. Battesti, B. Pinto Da Souza, S. Batut, C. Robilliard, G. Bailly, C. Michel, M. Nardone, L.Pinard, O. Portugall, G. Trénec, J.-M. Mackowski, G.L.J.A. Rikken, J. Vigué, and C. Rizzo, The BMVexperiment: a novel apparatus to study the propagation of light in a transverse magnetic field, Eur.Phys. J. D (2007) DOI: 10.1140/epjd/e2007-00306-3

[2] :S. Batut, J. Mauchain, R. Battesti, C. Robilliard, M. Fouché, and O. Portugall, .A TransportablePulsed Magnet System for Fundamental Investigations in QuantumElectrodynamics and ParticlePhysics, IEEE Trans. Appl. Supercond, 20th International Conference on Magnets Technology, paper4A05.

[3] R. D. Peccei and H. R. Quinn, Phys. Rev. Lett. 38, 1440 (1977); J.Preskill, M.B. Wise and F.Wilczek, Phys. Lett. B 120, 127 (1983); L.F. Abbott and P. Sikivie, Phys. Lett. B 120, 133 (1983); M.Dine and W. Fischler, Phys. Lett. B 120, 137 (1983); M.S. Turner, Phys. Rev. D 33, 889 (1986).

[4] E. Zavattini et al., Phys. Rev. Lett. 96, 110406 (2006).

[5] See e.g. http://axion-wimp.desy.de/index eng.html.

[6] K. Van Bibber et al., Phys. Rev. Lett. 59, 759 (1987).

[7] : C. Robilliard, R. Battesti, M. Fouché, J. Mauchain, A.-M. Sautivet, F. Amiranoff, and C. Rizzo,No ‘‘Light Shining through a Wall’’: Results from a Photoregeneration Experiment, PRL 99, 190403(2007)


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Magnetic Field Induced Second Harmonic GenerationSecond harmonic generation (SHG) of light is forbidden in isotropic media, like gases or liquids, andonly occurs in certain crystal classes. Applying an electric field to an isotropic medium makes SHGallowed. This phenomenon is used to create artificial SHG active media, and to measure thehyperpolarisability of molecules (electric field induced SHG, EFISHG). Theory predicts that applyinga magnetic field does not induce SHG, unless the medium is chiral (magnetic field induced SHG,MFISHG), but so far no experiments have been done.At the LNCMP, a setup has been constructed to investigate MFISHG. It uses a pulsed Nd:YAG laseras source, and a gatied photon counting photomultiplier detector. Last year, measurements have beenperformed on polymer films, doped with chiral molecules, using a small 2 Tesla electromagnet but noMFISHG was detected. In 2007, the magnet was upgraded to 4 T and the detection efficiency wasimproved, however, still no MFISGH signal was observed. In order to increase the signal strengthfurther, a high field, pulsed split coil magnet is being tested, that should allow a hundredfold increasein the SHG strength.

Pulsed field nuclear magnetic resonanceOver the past twenty years, very high field nuclear magnetic resonance (NMR) in the magnetic fieldrange of 20 to 40 T, beyond the reach of superconducting magnets, has provided a new important toolfor condensed matter research. The main drive behind this research is the exploration by NMR of newfield driven phenomena and field induced phases. Although in principle, NMR sensitivity increasesquadratically with magnetic field strength, in practice NMR in high field resistive magnets offers littlereal advantage in terms of sensitivity or resolution as compared to commercial lower fieldsuperconducting spectrometers, since restricted operation time of resistive magnets limits the amountof signal averaging that can be done and the spatial inhomogeneity of resistive magnets is of the orderof 20 ppm/mm. However these limitations do not impede NMR experiments in a large range ofcondensed matter systems, which typically have a high concentration of spins, with relatively largeintrinsic linewidths and are usually only available in small size. They are therefore suitable to bestudied by NMR in resistive or hybrid magnets.Very recently, it has been shown that solid state NMR free induction decay (FID) measurements canbe performed in pulsed magnetic fields, reaching fields up to 58 Tesla, by the group of J. Haase(formerly IFW, Dresden, currently University of Leipzig). As pulsed fields up to 89 Tesla areavailable, this breakthrough implies that the available field range for solid state NMR could now beextended to 80+ Tesla, opening many new and exciting possibilities to study new field drivenphenomena and field induced phases. Modifying an existing ultrasound spectrometer, we have built aprototype free induction decay spectrometer operating at 260 MHz with which we have observedsingle shot FID in niobium metal powder at 24,5 T in a standard Cu pulsed field coil with 40 ms risetime, as shown below, together with its Fourier transform.


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Semiconductors

Personnel involved:

Permanent: J. Galibert, J.M. Broto, B. Raquet, M. Goiran, H. Rakoto, M. Nardone, S. George.Non permanent: M. Millot

X t -Xl valleys crossover in AlP-GaP quantum wells

Collaboration: M. Semtsiv, T. Masselink (Institute of Physics, Humboldt University Berlin)D. Smirnov, G. Fedorov (NHMFL, Tallahassee)V. V. Rylkov (Kurchatov Institute, Moscow)

Despite its potential importance for optoelectronics applications, AlP is probably one of the last III-Vcompound for which the band parameters are still uncertain [1]. The band gap in AlP is indirect with aconduction band minimum 2.52 eV above the valence band edge. Only recently, we have establishedby high magnetic field spectroscopy of 2DEG confined in AlP/GaP quantum wells (QW) that bulkAlP X-valleys are located exactly at the edge of the Brillouin zone and in many respects, the valleysymmetry in AlP quantum wells (QW) with GaP barriers is similar to that of the AlAs quantum wellswith GaAs barriers [2]. As expected for such systems, the valley degeneracy is lifted into a single Xz-valley and a twofold Xxy-valleys, due to on one hand the valley-anisotropy confinement splitting andon the other hand the biaxial strain splitting caused by the lattice mismatch between AlP and GaP.Depending on whether the strain is tensile or compressive, splittings are additive or subtractive, thelater being the case for AlP on GaP. As a result, for wide AlP QWs the prevailing compressive straingives rise to a ground state Xxy-valley. In the present study, we have investigated [3, 4] the propertiesof quasi-two-dimensional electrons in a wide range of modulation-doped AlP quantum wells (between3 and 15 nm) with GaP barriers by measuring cyclotron resonance, quantum Hall effect, andShubnikov de Haas oscillations. The experiments down to 1.55K were performed under high pulsedmagnetic field while static fields were used for the low temperature transport measurements down to280mK.Figure 1 summarizes the CR data, by plotting excitation energy in the range between 1 and 6 meVversus resonant magnetic field, obtained at 4K on two different samples, one being a 15 nm widemulti-QW with 50 periods, and the other a 4 nm wide single-QW.

0 5 10 15 20 25 300

1

2

3

4

5

6

m*= (0.52 0.01m0

Ene

rgy,

meV

Magnetic field (T)

m*= (0.300.02)m0

Fig. 1. Values of the resonant fields determined from CR atdifferent excitation energies for the 15nm MQW structure (fullcircles) and the 4nm SQW (open circles).


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The two straight lines indicate parabolic conduction bands in the investigated energy range for both Xz

and Xxy valleys, the deduced cyclotron masses are mc1=0.300.02m0 and mc2=0.520.01m0

respectively. The iso-energy surfaces are then ellipsoids elongated along the line of the BZ withlongitudinal and transverse effective masses: ml/m0 = 0.90.02 and mt/m0 = 0.30.02.Regarding the valley degeneracy, a direct determination is derived for each QW from combination oflongitudinal and Hall resistances data. Fig. 2a shows Rxx(B) and Rxy(B) for the 10nm wide QW at1.55K while Fig.2b shows the same for the 3nm wide QW at 280 mK.The idea is to derive the filling factor assigned to each minimum of Rxx(B). This is obtained bymeasuring the Hall resistance at each minimum and finding the filling factor by the ratio v= RK /Rxy ,RK being the Klitzing resistance. In Fig2a, standing for the wide QW having the Xxy-valley populatedthe sequence of integer filling factors at consecutive resistance minima are marked by squares in termsof Rxy values. A remarkable feature of the found -series is its increment by 4 at low magnetic fields,high Landau quantum numbers, and then by one at low quantum numbers.

0 10 20 30 400

1x103

2x103

3x103

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22

5

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4

1418

T = 1,55KQW, t= 10nm Rxx

(

Rxy

(

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Rxx

(

Rxy

(

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1412 10

87

6

5

4

3QW, t= 3nm T = 280mK

Fig. 2. Rxx(B)and Rxy(B) for SQW having 10nm (a) and 3nm well width (b).

A straightforward interpretation is that Landau levels are, at low magnetic fields, degenerate by spin(2) and valley (gv) and this degeneracy is entirely lifted at high magnetic fields. Consequently, theLandau degeneracy value, 2xgv equal to 4 gives gv=2 for the Xxy-valley. Accordingly, a valleydegeneracy gv=1 is expected for the populated Xz-valley of the 3nm sample. This is preciselydisplayed by the data in Fig. 2b showing a sequence of filling factors incremented by 2 at lowmagnetic fields and by one at high magnetic field. Further experiments have revealed that the the Xt -Xl valleys crossover occurs at AlP QW thickness between 4 and 5 nm. The results are summarizedbelow in table I.


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The strain-induced splitting of Xt and Xl valleys is given by X = Xl - Xt = AlPu (e-e), where u is

the deformation potential; e and e are the relative strain values perpendicular and parallel to theepitaxial layers. Using the lattice constants of AlP and GaP we determine eand e. Calculated levelsplitting — using the masses, measured by cyclotron resonance — due to quantum confinement rangesbetween 17 meV and 23 meV, varying AlP well width from 5nm to 4nm. At some point in this range,strain induced splitting and confinement cancel each other; thus we have estimated the deformationpotential AlP

u ≈3.3eV.

References:

[1]. I. Vurgaftman, J. R. Meyer, and L. R. Ram-Mohan, J. Appl. Phys. 89, 5815, 2001[2]. M. P. Semtsiv, S. Dressler, and W. T. Masselink, V. V. Rylkov, J. Galibert, M. Goiran, and J.

Léotin. Phys. Rev. B 74, 041303(R), 2006.[3]. Goiran M., Semtsiv M.P., Dressler S., Masselink W.T., Galibert J., Fedorov G., Smirnov D.,Rylkov V. V., Léotin J. Proc 13th Int. Conf Narrow Gap Semiconductors « NGS 13 » Guilford UKJuly 8th 12th, 2007

Investigation of mass enhancement of 2DEG in Si-(111) MOSFET.

Collaboration: V. Dolgopolov, Institute of Solid State Physics, Chernogolovka.

A drastic increase of the effective electron mass with decreasing electron density has beenfound in strongly correlated 2D electron systems of Si-(100) MOSFETs in different experiments. Dueto this, there has been recently a revival of interest to (111)-silicon MOSFETs. Although the latterelectron system has been under study for quite a long time, the main experimental results wereobtained some decades ago, when the knowledge of the 2D electron systems left to be desired.Electron densities and temperatures used in experiments were not low enough and the experimentalaccuracy achieved for low-mobility samples was not high enough.We report on measurements of the product g*m*/gm in a dilute 2D electron system in (111)-silicon byinvestigating of the resistance in parallel magnetic field. Experiments were performed in an dilutionrefrigerator with a base temperature of 100 mK on (111)- silicon MOSFETs. Sample has the Hall bargeometry with width 400 µm equal to the distance between the potential probes. Application of a dcvoltage to the gate relative to the contacts allowed one to control the electron density. Oxide thicknesswas equal to 1500 °A.The resistance, Rxx, was measured by a standard 4-terminal technique. To check electron density as afunction of gate voltage the measurements of Shubnikov de Haas oscillations in normal magnetic fieldwere used.


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Fig.1.

In Fig.1 we show normalized original data scaled along X-axes. Such procedure allows toextract the ratio the field of total spin polarization (see Fig.2.), which is proportional to the productm*g*/mg.

Fig. 2.

The main result of these preliminary experiments is the observation of the zeroing of the field Bc at afinite electron density what is consistent with the mass divergence found in Si (111) MOSFETs.

Peculiarities of the electron transport in InMnAs layers

Collaboration: B. Aronzon, V.V. Rylkov (Russian Research Center “Kurchatov Institute”)

III-V magnetic semiconductors containing Mn impurities at large concentration (~1021 cm3) areperspective materials for the creation of new spintronics devices. Due to high Mn concentration thesesystems represent strongly disordered materials, the disorder being connected not only with therandom distribution of the Mn acceptor impurities, but also with their strong compensation caused bythe metastable donors state of Mn and by growth defects. The large-scale fluctuation potentialresulting in a non-uniform distribution of the charge carriers, promotes a local ferromagnetic orderingat low temperature that makes the analysis of the magnetic state of the system on the basis of themagnetization measurements rather difficult. The preference is now given to the investigation of thetransport properties and, in particular, to the study of the anomalous Hall Effect (AHE) [1] with theaim to define a magnetic state of the given systems and to estimate the spin polarization of carriers inthese materials.The study of magnetotransport properties of p-InMnAs layers under magnetic fields up to 30 T revealsthat, though the conductivity of samples falls when the temperature decreases, the AHE resistance inthe paramagnetic state appears to be larger in strong fields (> 20 T) than in the ferromagnetic state (T≤40 K) [2]. We have also established that the negative magnetoresistance is saturated in fields ofabout 10 Т at Т 4.2 K, whereas the AHE saturation is reached for 2 Т at Т30K. At 10 Tesla, themagnetoresistance drops by one order of magnitude. These results are interpreted by the non-uniformdistribution of the Mn impurities, which results in the formation of ferromagnetic islands and in thepercolation character of the films conductivity under conditions of strong fluctuations of the exchangeinteraction. Characteristic scales of the magnetoelectric non-uniformities are estimated from theanalysis of the mesoscopic fluctuations of non-diagonal components of the magnetotransport tensor.


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References:

[1] T. Jungwirth, Jairo Sinova, J. Mašek, J. Kučera, A.H. MacDonald, Rev. Mod. Phys. 78, 809(2006).

[2] V.V. Rylkov, A.S. Lagutin, B.A. Aronzon, V.V. Podolskii, V.P. Lesnikov, M. Goiran, J. Galibert,B. Raquet, J. Léotin. Submitted to JETP; Preprint Cond-Mat. No. 0612641 (2006).

Magneto photoluminescence under high hydrostatic pressure on InSe

Collaboration : Pr. Alfredo Segura (Valencia ), Samuel Gilliland (Valencia)

We have recently developed a new diamond-anvil-cell specially designed for simultaneous highpressure up to 10 GPa, low temperature (4 K) and high magnetic field experiments.Magneto photoluminescence experiments have been successfully carried out on the layeredsemiconductor InSe.The particular feature of the electronic structure of this compound is the dramatic modification of thevalence band maximum at pressures above 4 GPa, giving rise to an unconventional direct -to-indirectcross-over, characterized by the emergence of a new valence band minimum with a ring-shaped(toroidal) constant energy surfaces, affecting both the optical and transport properties. High magneticfield experiments including cyclotron resonance, photoluminescence (PL), magneto-transport andphotoconductivity should allow for an accurate determination of the shape and band-structureparameters of the ring shaped VBM.In a preliminary analysis of the obtained results, a similar behaviour to that reported by Goñi et al. [2]was observed. Two Gaussian functions were fitted to model the free and bound excitons, as in [3], anda quadratic fitting of the bound exciton energy (E in eV) as a function of the pressure (P in GPa) gavethe following relationship:

The Hall resistance versus magnetic fielddependencies of the InMnAs film at differenttemperatures: 1 – T=25 K, 2 – T=40 K, 3 –T=88 K. The insert shows the RH(B) curve atT = 25 K in expanded scale.

Specific resistance versus magnetic fielddependencies of a InMnAs film at differenttemperatures: 1 – T=25 K, 2 – T=40 K, 3 –T=88 K. Insert : magnetoresistance atT=4.2 K.


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E = 1.338 – 0.00808 P + 0.00379 P2 (1)

On applying high magnetic field, a slight increase in PL intensity was detected, due to the increase inthe density of states caused by Zeeman splitting. Figure 1a shows that the energy of the bound excitonincreases almost linearly in function of field, whereas the variation in the constant of proportionality isnon-linear. Up until 4 GPa, this coefficient is either constant or increases slightly with pressure,perhaps due to a decrease in the electron effective mass. However, the abrupt decrease in thecoefficient after this pressure coincides well with the aforementioned direct-to-indirect cross-over [4].

[1] D. Errandonea et al., Physical Review B 71, 125206 (2005).[2] A. Goñi, A. Cantarero, U. Schwarz, K. Syassen and A. Chevy. Phys. Rev. B 45, 4221 (1992).[3] J. Riera Guasp, PhD Thesis, Universidad de Valencia (1990).[4] F. Manjón, A. Segura, V. Muñoz-Sanjosé, G. Tobías, P. Ordejón and E. Canadell. Phys. Rev. B70, 125201 (2004).

Outlook

In AlP/GaP heterostructures we intend now to investigate the QW energy spectrum by direct inter-subband spectroscopy.The electronic correlations in 2DEG will be studied in this system through high magnetic fieldmagneto-transport in parallel configuration; preliminary results have already been obtained. This topicwill also be developed in Si-(111) MOSFET by the extension of the measurements up to 55T.The current activity on the diluted magnetic semiconductors should now be focussed on twodimensional structures.It is also planned to study the magneto-luminescence of QD under high pressure.

0 1 2 3 4 5 6

0,0

0,1

0,2

0,3

0,4

Directgap

Indirectgap

Mag

netic

coef

ficie

nt(m

eV/T

)

Pressure (GPa)0 10 20 30 40 50 60

1,331,341,351,361,371,381,391,401,411,421,431,441,451,461,47

5.05 GPa

2.83 GPa

0 GPa

0.53GPa 1.06GPa

5.70 GPa

1.85 GPa

Bou

ndex

cito

nen

ergy

(eV

)

Magnetic field (T)Variation of the bound exciton energyversus magnetic field at 4.2K.

Variation of the proportionality coefficient asa function of pressure at 4.2K.


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Biophysics

Personnel involved:

Permanent: E. Haanappel

Collaboration: V. Le Berre, N. Marsaud, J.-M. François, (Plateforme Biopuces, Génopole ToulouseMidi-Pyrénées, INSA, 135 avenue de Rangueil, 31077 Toulouse Cedex 04)

Effect of a high magnetic field on a biological system: the case of yeast

Despite decades of research and a vast literature, the effect of a magnetic field on living matter is stilllargely a matter of controversy. This represents an important public health issue, as electromagneticfields have been blamed for certain adverse effects like e.g. an increased likelihood of childhoodcancer. In the field of health care, patients receiving MRI (Magnetic Resonance Imaging) scans areexposed to static high magnetic fields of several Tesla. MRI has been deemed safe for patients, despiteevidence that certain cells or developing eggs are influenced by a strong magnetic field. To assess thesafety of high magnetic fields, we have studied their effect on genetic expression, mortality andmorphology changes of yeast.

Yeast is a unicellular eukaryote and a well-studied model organism for higher organisms like humans.In collaboration with researchers from the Biochip platform of the Genopole in Toulouse, we havestudied whether high magnetic fields could affect yeast. Our initial experiments have not shown anydifferential gene expression for all approximately 6400 genes of the yeast genome. We have extendedthese experiments by studying other field exposure protocols and also by introducing additional tests,looking for increased mortality and changes in morphology in yeast after high magnetic field exposure.Cultures of living yeast cells, harvested in the exponential growth phase, were exposed to strongmagnetic fields. The experiments were done at a temperature of 27°C, the yeast cultures weremaintained at this temperature in a specially designed cryostat to avoid thermal shock. In our initialexperiments, we have studied exposure to a single 37 T field pulse or to a 14 T static field for 30minutes. In our follow-up experiments, we have also studied the effect of multiple field pulses (20 Tpulses, from 1 to 4 in rapid succession) and long-term exposure, 14 T for 8 hours. In all protocols,controls were not exposed to the magnetic field but otherwise subjected to the same treatment as theexposed samples. Immediately after exposure to the magnetic fields, we checked for mortality bystaining about 5% of our cultures with methylene blue, which collects in dead yeast cells. We did notobserve any increase of mortality for any exposure protocol. The remaining part of the cultures wascentrifuged and the collected yeast was quickly frozen in l-N2. Subsequently, the total RNA wasextracted from the frozen pellet by grinding. The isolated RNA was analyzed using DNA arrays,capable to detect, for each gene in an organism’s genome, the extent of gene expression. Within a 95%confidence limit, we could not detect any significant differences between exposed and unexposed cells.These results therefore suggest that high magnetic fields do not lead to increased mortality and do notinfluence gene expression in yeast under the conditions that we have examined.


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High Field X-ray experiments

Personnel involved:

Permanent: F. Duc, P. Frings, J. Billette, M. Nardone, S. George, L. Drigo, G.L.J.A. Rikken

Non permanent: K. Chesnel, A. Zitouni

Collaboration: C. Detlefs, T. Roth and O. Mathon (ESRF), J.E. Lorenzo (Institut Néel, Grenoble), J. Vanacken(INPAC, Leuven), Z.A. Kazeĭ(Moscow State University, Russia), P.C. Canfield (Ames Laboratory, USA), R.Stern (National Institute of Chemical Physics & Biophysics, Tallinn, Estonia), J.C. Trombe and J. Galy (CEMES,Toulouse), P. Algarabel (ICMA, Zaragoza).

Synchrotron X-ray powder diffraction in high magnetic fields:

High magnetic field effect on the Jahn-Teller state in TbVO4

We have directly observed for the first time the effect of magnetic fields on the Jahn-Teller (JT)distortion of TbVO4. These results have been obtained at the ESRF by means of synchrotron x-raypowder diffraction experiments in pulsed magnetic fields. Contrary to spectroscopic and magneticmethods, X-ray diffraction directly measures the JT distortion; the splitting between the (311)/(131)and (202)/(022) pairs of Bragg reflections of TbVO 4 (near 11.8° and 12.6°, respectively) isproportional to the order parameter. In order to quantitatively describe the effect outlined above wehave performed comprehensive mean field calculations of the magnetoelastic distortion of TbVO4 as afunction of the strength and direction of the externally applied magnetic field. Due to thepolycrystalline nature of the sample and its strong magneto-crystalline anisotropy the calculatedspectra (fig. 1) had to be averaged over all possible orientations of the powder grains relative to theapplied magnetic field. The applied magnetic field was found to influence both the magnitude of theorder parameter, as observed in the splitting of the (311)/(131) and (202)/(022) pairs of Bragg peaks,and the relative domain populations, reflected in the intensity ratio between the partners of a pair. Ourtheory is in qualitative agreement with the experimental results, even though small quantitativediscrepancies persist (fig. 1 and 2).

Fig. 1: Comparison between calculated andmeasured spectra for different temperatures andfields. A T = 39K and 30T, the dotted curve (in red)corresponds to the calculations including themagnetocaloric effect, and the green line to thecalculations with the magnetoelastic constantreduced by 25%.

Fig. 2: Average order parameter =2(a0-b0)/(a0-b0) as afunction of applied magnetic field for selectedtemperatures. The splitting between the (311)/(131) and(202)/(022) pairs of Bragg reflections was used todetermine the orthorhombic lattice parameters a0 andb0 . Continuous lines: experimental data. Dashed lines:theory.


- 34 -

This new technique was found to be a powerful tool to study JT systems, and allows us to observe newaspects of magnetic behaviour of the classical and well studied JT compound TbVO4. These highmagnetic field data may be used both to revise known theoretical models and to develop new,improved ones.

Structural transition in BaCuSi2O6 below 30KX-ray powder diffraction experiments under pulsed magnetic fields have been carried out on the HanPurple BaCuSi2O6. These experiments have been performed on ID20 at the ESRF using the secondsetup for diffraction measurements in pulsed magnetic fields. Thanks to the conical ends of the magnetcoil, this setup offers a larger optical access (x-ray scattering angles, previously limited to 13°, can beextended up to 36° (fig. 3)).BaCuSi2O6 is a quasi-2D compound composed of copper silicate planes separated by barium ions.Within the copper silicate planes, Cu2+ ions are arranged in vertical dimers, such that the material has asinglet ground state with a large gap to the lowest excited triplet state. Magnetic fields in excess of H c1

~ 23T close the spin gap, such that cooling in a large applied field results in a state characterized bylong-range magnetic order. Recent studies [1] indicate that it is possible to describe this phasetransition in terms of Bose-Einstein Condensation (BEC) of delocalized triplets. Unfortunately, thelarge spin gap of this material currently precludes any direct measurements of the magnetic structurein the ordered state. More recently, high-resolution x-ray diffraction experiments performed at theAdvanced Photon Source on single crystal of BaCuSi2O6 have clearly revealed a structural phasetransition below ~100K [2]. This transition is characterized by an orthorhombic distortion of the room-temperature tetragonal structure, and the appearance of an additional incommensurate latticemodulation. The phase transition is first order and exhibits considerable hysteresis [2].

Fig. 3: Diffraction signal of BaCuSi2O6 at 5K. Single exposure of 3.6 ms. Left: portion of a raw image showingthe Debye rings. Right: 2-scans obtained from the raw images by integration of the Debye rings.

We have performed x-ray powder diffractionexperiments in pulsed magnetic fields in thetemperature range from 5 to 120K withmagnetic fields varying between 5 and 30T.Our measurements did not reveal any clearsignature of field-induced structural phasetransition. However, an additional Braggreflection (fig. 4) was observed on alldiffraction patterns between 15 and 30K (withand without applied magnetic field) suggestingthe existence of a structural phase transitionbelow 30K. Further high resolution x-raydiffraction experiments (without magneticfield) are needed to confirm this result and todetermine the low temperature structure ofBaCuSi2O6.

Fig. 4: Detail of the diffraction patterns ofBaCuSi2O6 at different temperatures. An additionalBragg reflection is clearly visible between 15 and30K.

(008)


- 35 -

[1] M. Jaime, V. F. Correa, N. Harrison, C. D. Batista, N. Kawashima, Y. Kazuma, G. A. Jorge, R.Stern, I. Heinmaa, S. A. Zvyagin, Y. Sasago, and K. Uchinokura, Phys. Rev. Lett. 93, 087203 (2004).[2] E. C. Samulon, Z. Islam, S. E. Sebastian, P. B. Brooks, M. K. McCourt Jr., J. Ilavsky and I. R.Fisher, Phys. Rev. B 73, 100407(R) (2006).

High field x-ray powder diffraction on MnV204

X-ray diffraction experiments under high pulsed field have been performed to investigate thestructural properties of spinel compounds, which exhibit structural, orbital and magnetic phasetransitions induced by intense magnetic field. We have more specifically studied the MnV2O4 system,a spinel oxide, in which large magnetostrictive effects has been observed, as well as structural phasetransition induced by moderate magnetic field occurring just above the critical temperature. While it issuggested that these effects derive from strong spin-orbit couplings at the atomic scale combined withexchange couplings between Mn and V spins, the microscopic mechanism of the structural orderingunder magnetic field is not fully understood. We have been interested to investigate these aspects,using the diffraction tool, probing the microscopic properties of the system under higher field valuesup to 30T (studies reported in the literature not exceeding 5T).Diffraction experiments under high pulsed field have been carried out on MnV204 polycrystallinesample at ESRF beamline ID20, with 20keV light. We have performed measurements at lowtemperatures, cooling the system down to 20K through the structural transition around 55K. At hightemperature, the structure is cubic and undergoes a structural transition to tetragonal phase at lowtemperature. This structural transition is first order, and presents strong hysteresis. We measured atemperature gap T of 8K between the heating and cooling critical points. The diffraction spectrashow that in the region of the transition, a mixture of cubic and tetragonal phases is present in thematerial, as shown in the figure 5 top panel.We have studied the variation of the respectiveproportions of cubic and tetragonal phaseswithin the transition region along major andminor temperature hysteresis loop, which canprovide further information about themicroscopic process of the structural transitionoccurring in the polycrystalline system.

We have also studied the diffraction signalunder the application of magnetic field up to30T, within the region of the transition at 55Kafter a series of hysteresis loop in temperature.We have observed significant changes in thediffraction diagram with the field, revealingprogressive structural changes. Figure 5bottom panel shows the variation of theproportion of tetragonal phase over the cubicphase with the magnetic field. The resultsshow an increase of the tetragonal phase,suggesting a plateau around 2 0T and a sharperincrease at larger field values. It also shows astrong remnant effect when the magnetic fieldis released at H = 0T.These diffraction data have been completed bymagnetometry measurement performed at theLNCMP, characterizing a paramagneticbehaviour at high temperature, and transitionto an antiferromagnetic behaviour at lowtemperature.

Fig. 5: top panel: cell parameters for the cubic andtetragonal phases versus temperature. Bottompanel: Variation of the ratio of tetragonal overcubic phase (quantified on the (004) Bragg peak)versus magnetic field measured at 55K


- 36 -

All these observations are under more detailed analysis, and should bring more detailled informationabout the microscopic behaviour occurring in the field induced phase transition.

Absorption spectroscopy and X-ray magnetic circular dichroïsm (XMCD) in pulsed magneticfields

Magnetocaloric effect (MCE), or adiabatic change of temperature in magnetic material under theapplication of magnetic field, has been discovered over a century ago [1] and has more recentlymotivated scientific interests as it offers excellent potential for magnetic refrigeration [2]. In particular,giant MCE has been evidenced in the Gd5(Si2Ge2) compound, with extremely large magnetic entropychanges [3]. While exceeding the reversible limit and exhibiting hysteretic behaviour, these effects areassociated to a first order ferromagnetic phase transition. These observations have instigated the studyof structural modifications and volume variation accompanying the magnetic transitions.Magnetostructural phase transitions have been indeed evidenced in Gd5(SixGe1-x)4 compound fordifferent compositional ranges, indicating crystallographic lattice modifications along with aparamagnetic (PM) to ferromagnetic (FM) phase transition [4]. Those observations have been obtainedby combining traditional X-ray Diffraction (XRD) measurements with calorimetry and magnetometrymeasurements.While the current knowledge of the magnetostructural effects occurring with the MCE is mainlymacroscopic – the XRD measurements giving the average crystallographic information, magnetometryand calorimetry providing macroscopic probes- it is useful to understand the microscopic origin ofthese magnetocrystalline phenomena at the atomic scale, using in particular element sensitivetechniques and local probes. This is possible via X-ray spectroscopy techniques, as EXAFS andXMCD, available at the ESRF. We are therefore interested to investigate the Gd5(SixGe1-x)4 systemwith those techniques to obtain unique information on the microscopic properties. By performingXANES and EXAFS measurements at the Gd L edges, we probe the charge density distribution andinteratomic distances around the Gd atoms within the crystallographic lattice. In addition XMCDmeasurement at Gd-L2 and Gd-L3 edges allows to study the magnetic anisotropy and to discriminatethe spin and orbital components of the magnetic moment at the Gd sites. Ultimately, we follow theevolution of those parameters during the phase transitions, and their variation with the temperature Tand the applied magnetic field H.

In this experiment, we studied a Gd5Si1.8Ge2.2 compound, ranging in the compositional range of 0.24<x<0.5, for which an orthorhombic to monoclinic crystallographic phase transition occurssimultaneously with the ferromagnetic to paramagnetic transition [5]. In this system, a shearmechanism involving two different pathways for the structure transformation on the Gd-Si covalentbond has been suggested [6, 7]. We proposed to validate those suggestions with the element and localsensitivity provided by EXAFS and XMCD. In order to map the structural and magnetic propertiesthrough the transitions in (H, T) phase space, we performed these measurements at differenttemperature points ranging from 100K to 250K, and applying magnetic field with small steps up to30T.

The implementation of the experiment required the application of high magnetic fields in cryogenicconditions, and the generation of EXAFS and XMCD spectra in quick way for each (H, T) point. Thiswas possible at the beamline ID24 at the ESRF, with the combination of the mobile pulsed fieldinstallation and a unique spectroscopic dispersive setup available at this beamline. The high magneticfields were produced by a pulsed coil already implemented on ID20 [8]. Using this technique, it hasbeen possible to record XMCD spectra on Gd sample at Gd L3 edge, at temperature down to 5K andunder magnetic field up to 30 Tesla. These features are perfectly suited with the requirements of ourexperiment. XMCD measurement under high pulsed magnetic field is fully compatible with thecharacteristics of the Energy dispersive beamline ID24 (flux, integration time and timing sequence) asthe dispersive technique offers the unique advantage that the entire spectrum is acquired within onesingle pulse during the magnetic field pulse. Compared to the classical energy scanning technique, thetotal number of magnetic pulses required by using energy dispersive technique is thus strongly


- 37 -

reduced, extending the fatigue-limited lifetime of the setup, and leading to very efficient dataacquisition.

The experiment on Gd5Si1.8Ge2.2 has been successfully carried out on December 2007 at ESRF ID24,and is being analyzed. The figure 6 shows an absorption spectra and XMCD signal recorded at the Gd-L3 edge at 300K and under 30T. At 300K, the system is above the Néel point (about 250K) in aparamagnetic state. The result in figure 6 shows that intense magnetic field induces a transition intothe ferromagnetic state, as reflected by the XMCD signal.

Fig 6: Absorption and XMCD spectra at the Gd L3 edge measured on Gd5Si1.8Ge2.2 at 300K

[1] E. Warburg, Ann. Phys. 13 (1881) 141[2] V.K. Pecharsky and K.A Gschneidner, Jr., J. Magn. Magn. Mater. 200, 44 (1999)[3] V.K. Pecharsky and K.A Gschneidner, Jr., Phys. Rev. Lett. 78, 4494 (1997)[4] F. Casanova et al., Phys. Rev. B 69 104416 (2004)[5] L. Morellon et al. Phys. Rev. B 58, R14721 ( 1998)[6] V.K. Pecharsky and K.A Gschneidner, Jr., J. Alloys Compd. 260 (1997) 98-106[7] W. Choe et al, Phys. Rev. Lett. 84, 4617 (2000)[8] Mathon et al, in preparation (2007).

Technical improvement:

Vibrations characterization and minimization

Our first EXAFS and XMCD experiments performed under high pulsed field at the dispersivebeamline ID24 at the ESRF on Gd foil (December 2006) and URhGe monocristal (February 2007)showed that the feasibility and the quality of the measurement strongly depend on the mechanicalstability of the experimental setup. This high sensitivity to mechanical stability derives from thespecific features of the beamline ID24, more particularly the use of a polychromatic dispersive lightthat is focused into a very small spot of 5 microns horizontally. In these geometrical constraints, theacquisition of absorption spectra under in-situ pulsed magnetic field is challenging because ofpotential vibrations and motions induced by the production of the high field pulse, therefore requiresexcellent sample homogeneity and position stability within the beam focal spot.

In order to characterize the sample vibrations induced by the field pulses in our cryomagnet, weimplemented an optical probe setup to measure the motions at the sample position in real conditions.The principle of this setup consists in producing a visible light spot at the sample position andfollowing the spot motions with position sensing detector as described on figure 7. In our setup, thelight is produced by a 630nm diode laser, and transmitted inside the cryomagnet at the sample positionvia an optical fiber of 50 microns core. The light exiting from the fiber is collimated by a micro-lens(focal length of 8mm) placed at the sample position. The light motions are measured with a 4quadrants photodiode detector mounted on a positioning stage close to the cryostat exit flange.


- 38 -

Horizontal and vertical position deviations are estimated from linear combinations of the intensitiesmeasured on the 4 quadrants. The detection signal is synchronized with the magnetic field pulse.

A series of vibrations measurements has been performed at the ESRF beamline ID24 under realisticexperimental conditions. The measurements with our optical setup have been completed by additionalsimultaneous measurements performed with vibrometer and accelerometer devices operated by theESRF, providing complementary information on the motions seen from external point of view (outsideof the cryomagnet, detector, mounts, supports, floor etc). The setup has been tested in differentconfigurations in order to identify the different sources of motions and contribution to the signal. Thegraph in figure 7 presents the vibration signal measured in one configuration where the photodetectoris mounted at 20cm from the sample position, on a separate plate. The graph shows the horizontaldisplacement Dx and vertical displacement Dz measured on the detector as a function of time duringthe magnetic field pulsed, represented by the pickup coil signal (in green). The signal exhibit anoscillatory behaviour, with characteristic frequencies about 35Hz, modulated by lower frequencycontribution at 7.5 Hz. In that configuration, the apparent displacements reach an amplitude of 475microns in the vertical direction and 325 microns in the horizontal direction at maximum. Weattribute the low frequency signals to cryostat vibration modes as well as mounting vibration modes,and higher frequency signal to vibrations occurring inside the cryomagnet induced by the coil pulse.The amplitude of the signal might be amplified by mechanical resonances. Additional test withdetector attached directly to the flange show that the amplitude of displacement in that case does notexceed 50microns both in vertical and horizontal directions. Furthermore in all the tests, the measuredsignal show that the displacements remain smaller than 40 microns during the first 20 msec, while thefield is applied and reaches its maximum.

Fig. 7:Left: Setup for the vibration tests at ESRF. Right: Measurement of the vertical and horizontal motions intime during a 30T field pulse

To reduce the observed vibrations effects in the setup, modifications of the cryostat design andmechanical improvement are under study. The vibrations effects have been already drastically reducedform the initial configuration (where they exceeded 1mm) by consolidating the cryostat internal tubewith the chamber holding the coil. Absorption experiments have been successfully performed inDecember 2007 at the ESRF on powder samples, as well as on an amorphous film.


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High Strength Conductors

Personnel involved:Permanent: N. Ferreira, J.M. Lagarrigue, F. Lecouturier, L. Bendichou, J.P. LaurentNon permanent: M. Mainson (CDD), J.B. Dubois (Ph.D)

Research & Development of high strength composite conductors

Copper alloys for magnets with optimized current distributionConductors made of copper alloys like GlidCop or CuAg (with low silver content 0.08%) have beenpurchased from industrial companies in order to be combined with Zylon fibers in magnets withoptimized reinforcement distribution. Kapton insulation has been applied to perform electricalinsulation.

CuNbTi microcomposite wires for conventional magnets and split-coilCollaborations: C. Verwaerde (MSA), H. Jones (Clarendon Laboratory, University of Oxford)

During this year, a strong link has beendeveloped with industrial companies in orderto adapt commercially available “rawmaterials” to the specifications of magnetsgenerating high pulsed magnetic fields.CuNbTi high strength conductors have beenprovided by an industrial company. First, aselection of round samples from LHCproduction has been characterized in liquidnitrogen at LNCMP. The good level ofmechanical properties (UTS>1GPa at 77K)promotes them as potential candidates forpulsed magnets. Rectangular cross sections of2.00mm * 3.15mm have been transformed.Their properties, with two kinds of insulation(polyester fibers braiding or polyimide(Kapton) ribbons) are summarized in thefollowing table.Mini-coils wound with CuNbTi conductorswill be tested in order to compare their agingperformances versus the Cu/SSmacrocomposite ones. They also allow tocompare two materials for insulation: polyesterfibers and Kapton ribbons. Moreover, wetwinding impregnation (LNCMP) and vacuumimpregnation, performed in the ClarendonLaboratory (University of Oxford) in theframework of the DeNUF project, have beenapplied to the polyester insulated mini-coils.

Insulation Polyester braiding Kapton ribbons

UTS ( RT) 929 MPa 738 MPa

UTS (77K) 1246 MPa 1027 MPa

RT) 3.0380 µohm.cm 2.9042 µohm.cm

77K 0.4035 µohm.cm 0.3568 µohm.cm

2.00mm * 3.15mm cross section of CuNbTi wires

Mini-coil wound with polyester insulated CuNbTi


- 40 -

Coil aging studies within DENUF project (see also “magnet” paragraph)The study of the influence of the work-hardening on copper/ stainless macrocompositeconductors has been performed in order todetermine the best compromise betweenstrength and plastic strain with respect to thecoil lifetime. Several small batches (50 meters)of high strength conductors made of copperand stainless steel with different work-hardening ratio (RA= 65%, 70%, 75%, 80%;RA=[(Ai–A)/Ai ]*100, Ai is the cross sectionat the previous annealing stage) have been

2.00mm * 3.15mm cross section of CuSS wires

elaborated in-house and insulated by anindustrial company with a double layer ofpolyimide films (Kapton).

Four coils, with RA= 65%, 70%, 75%, 80%,have been aged at 90%Bmax.The resistancemonitoring data are plotted versus the shotsnumber in the following graph. For each coil,we observe that the increase of the electricalresistance shows a tendency to saturate near9% after 100 shots. Then, two regimes areevidenced:- when B increases,R is smaller for the mostcold-worked wires (80%)- during aging, R is higher for the most cold-worked wires (80%)Moreover, there is a more or less rapidtransition ranging from 1% to 8% of resistanceincrease, depending on the conductor’sfeatures. The plastic aging monitored by FiberSensor Monitoring is in agreement with theresistance monitoring.

RA(%), Kapton insulation 65 70 75 80

UTS ( RT) MPa 755 783 796 856

UTS (77K) MPa 1016 1041 1074 1073

Resistance variation, at 77K, versus shot numberfor different CuSS mini-coils aged at 90%Bmax

Ultra-high strength nanocomposite Cu/Nb conductors

Cu nanowhiskers embedded in Nb nanotubes inside a multiscale Cu matrix: the way to reachextreme mechanical properties in high strength conductorsCollaborations : L. Thilly (LMP, Poitiers), V. Vidal (MTM, Leuven)

For the development of non destructiveresistive pulsed magnets over 80T, optimizedreinforced Cu/Nb/Cu conductors composed ofa multi-scale Cu matrix embedding Nbnanotubes were produced by Severe PlasticDeformation. TEM reveals good co-deformation compatibility between thereinforcing Nb nanotubes and the multi-scaleCu. While a sharp single-component <110>fibre texture is developed in Nb nanotubes, adouble texture with <111> and <200>orientations is observed in copper matrix. The

mechanical properties are improved comparedto nanofilamentary Cu/Nb wires. Theextraordinary strengthening of the co-cylindrical structure seems to be related to: (i)an increase of Cu-Nb interfaces surface actingas dislocations barriers; (ii) a rapid andcontrolled access to nanometre scale wheresize effect operates on the plasticitymechanisms; (iii) the contribution of anadditional reinforcing phase: the Cu-fnanofilaments embedded in the Nb nanotubesbehave as whiskers with strong sizedependence. The Cu/Nb/Cu system is therefore

R% vs Shot number

98,000

100,000

102,000

104,000

106,000

108,000

110,000

0 20 40 60 80 100 120 140 160

Shot number

100*

R/R

0

Coil25 (65 %) Bmax= 41,44 vieillissement a 93,5% Coil2 (80%) Bmax=43 vieillissement a 89,6%Coil29 (70 %) Bmax= 41 vieillissement a 90,2% Coil28 (75 %) Bmax= 41,60 vieillissement a 90,1%


- 41 -

more efficient than the Cu/Nb system for thehigh- strength applications in magnets: itexhibits a controlled microstructure and anefficient strengthening in the nanocompositezones, where size and also geometry playmajor roles.Finally, the validity of the Cu/Nb/Cunanocomposite wires (N=853, 1mm),insulated with Kevlar fiber), without any lossin strength, has been demonstrated in thethumb-coils configuration (Ph.D work of S.Batut, see also “magnet” paragraph). Firstneutrons diffractions experiments onCu/Nb/Cu aged coils have been performed atthe continuous spallation neutron source SINQ(POLDI, Paul Scherrer Institut, Switzerland)and have to be completed.

(a), (b), (c) SEM image of the multi-scalestructure of Cu/Nb/Cu co-cylindrical wires (N= 853, d=1.511mm). (d) High-magnifica-tioncross-section SEM image of the nano-composite area show-ing the Nb nanotubes,the Cu fibers and the interfilamentary Cu

Evidence of internal Bauschinger test in Cu/Nb/Cu nanocomposite wires during in-situmacroscopic tensile cycling under synchrotron beamCollaborations : L. Thilly & P.O Renault (LMP, Poitiers), V. Vidal (MTM, Leuven), H. VanSwygenhoven & B. Schmitt (Swiss Light Source, Paul Scherrer Institut)

In-situ multiple tensile load-unload cyclesunder synchrotron radiation have beenperformed on nanocomposite Cu/Nb/Cuwires. The phase specific lattice strains andpeak widths demonstrate the dynamics of theload-sharing mechanism where the fine Cuchannels and the Nb nanotubes store elasticenergy, leading to a continuous build-up ofinternal stress. The in-situ technique allowsrevealing the details of the macroscopicallyobserved Bauschinger effect.The macroscopic true stress-true strain curveof one of the CuNbCu samples is plottedbelow: the increasing hysteresis during tensileload-unload is the signature of large internalstresses that are built-up.Figure (a) shows the applied stress versus runnumber (i.e. versus time since one runcorresponds to a 30s collection of X-rays) withindication of the holding time in theloaded/unloaded states. Figure (b)demonstrates the evolution of the (220)diffraction peak position of the large and fine

Cu peaks versus run numbers and figure (c) theevolution of the (110) reflection in the Nbnanotubes. Already in the as-prepared state, thetwo Cu phases are in a different stress state:the fine Cu channels being in larger axialelastic compression than the large Cu channelssince 2220(fine-Cu) < 2220(large-Cu) <2220(annealed Cu) = 23.12°. The Nbnanotubes are in axial elastic tension:2110(Nb) > 2110(annealed Nb) = 12.60°. Notethat both equilibrium 2 values weredetermined by neutron scattering on annealedCu and Nb samples. Applying tensile load, thetwo Cu phases respond differently: the shift ofthe peak position of the large Cu stabilizesupon loading (fig(b)), evidencing a pronouncedplasticity regime whereas the fine-Cu peakexhibits only a slight deviation from linearbehaviour at highest stress.


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The Nb nanotubes clearly remain in the elastic regime, as is demonstrated by the linear behaviourof the peak position (fig. (c)). The material is therefore composed of three phases with distinct elastic-plastic behaviour, a situation that favours the development of internal stresses during co-deformation,as evidenced by the gradual change of the peak positions at each unloaded state: both the axialcompression of Cu channels and the axial tension of Nb nanotubes increase after each cycle.

Macroscopic true stress – true strain curve of Cu/Nb/Cu (N=853, 0.5mm) wires

Evolution versus run numbers (i.e. time) and loading-unloading cycles of: (a) true stress, with variousholding times at loaded/unloaded states; (b) position of (220) large-Cu and fine-Cu peaks; (c) positionof (110) Nb peak.

Outlook

The NANOFILMAG project, funded by the ANR during 36 months, has started in July 2007. It isdedicated to the optimization of the processing parameters of ultra-high strength copper/niobium basednanocomposite conductors. Five partners are involved: two CNRS mixed research unit (LNCMP,LMP), two CEA Laboratories (DAPNIA, LTMEX), and an industrial company (MSA).Effect of the nanostructuration of Cu/Nb wires on damage mechanisms under applied stress will alsobe addressed.In the framework of DeNUF, “new” conductors and “new” insulators will be systematically agedusing the mini-coil aging platform. In 2008, we plane to finish the aging on the CuNbTi mini-coils andto perform aging on CuAg high strength wires, provided by IFW (Dresden), and in-situ CuNb wiresprovided by HLD (Dresden) and Bochvar Institute (Moscow).


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High-field coils

Personnel involved:

Permanent: BILLETTE Julien, FRINGS Paul, GIQUEL Franck, LAGARIGUE Jean-Marc,

Non permanent: BÉARD Jérome, MAUCHIN Julien, BATUT Sebastien

Collaboration: DeNUF

The production of user coils.

In 2007 the copper-zylon coils became theworkhorse of the laboratory. The distributedreinforcement by zylon fibres of coils builtwith relatively "soft" wire proved for themoment to be the most reliable, efficient andeconomic way to produce fields of 60 T.During the year 6 coils of this type were built,some of them to equip new cryostats but themajority to replace coils that have failed afterintensive use. The successful introduction ofthe rapid-cooling technique reduced the timeimposed by the cooling of the coil after a pulseand permitted users to perform more pulses during their stay but at the same time resulting in a highercoil "consumption" since the maximum number of pulses that a coil can produce (of the order ofseveral 100's) is reached in a shorter time. Lifetime of coils stays an important (but only partlyunderstood) issue. In 2007 the first zylon coil ever used in Toulouse (tested in June 2001 andgenerating a field of 64 T) failed after several 1000's of high-field pulses leaving us puzzled whysimilar coils can have such different lifetimes. At the moment no clear explanation other thanstatistical fluctuations is available, but we try to investigate and experiment further in order to get abetter understanding of the factors that influence coil lifetime.Although the copper-zylon coils represent the majority of the coils used at the moment one should notforget that this approach alone might not be sufficient to reach the highest fields.

The production of special coilsSeveral special coils were built or used successfully. A large opening horizontal field coil permitted tosuccessfully increase the available scattering angle with X-rays at the ESRF Grenoble using fields of30 T. A split coil allowing an even larger scattering angle was designed and most of the parts werefinished in 2007. The winding of the coil and the assembling of the cryostat can hence be finalised inthe beginning of 2008. A coil of even more original construction (X-coil) permitted to successfullyexclude the existence of axion-like particles performing experiments at the LULI (ÉcolePolytechnique). To increase the product of field and length for this and the BMV experiment westarted a systematic study of the technical limitations of the actual design which will hopefully lead tobetter understanding of the "non-classical" coils and thus to their improvement.

75

125

175

225

275

0 50 100 150 200

time [min]

tem

pera

ture

[K]

classical coil1 cooling gap1 cooling gap scaled by 3simulation no gapsimulation 1 gap

Cooling time of a coil with a cooling gap – Measurement and simulation.


- 44 -

Improvements of user coils

The biggest improvement was the actual implementation of rapid cooling coils as user coils. Rapid-cooling coils reduce the cooling time by more than a factor of three. However, at first, we wereworried that the change to a less monolithic structure might cause negative effects on lifetime or onthe field noise (in high magnetic fields "free" lunches” do not exist). A systematic measurement of thefield noise, by using a PU coil with the surface area perpendicular to the field, proved that the cooling

annulus inside the coil did not increase the field noise. The same measurements also showed that for agiven bore and maximum field there was no difference in noise-level between copper-stainless-steelcoils and copper-zylon coils. The archiving system for pulses permitted us to more precisely followthe lifetimes of our coils and at the moment we do not have any indication that rapid-cooling coilsshow a shorter lifetime than classical coils (non-rapid cooling or copper-stainless steel).

The first Cu Zy coil ever tested in Toulouse (builtJune2001June 2007).

Design of the split coil with vertical field.

Cooling gaps in the flanges


- 45 -

Although making the highest magnetic fields should not be a goal to be realised at all costs we actuallyinvest in efforts to keep the "European record" (mono-coil >79 T, duo-coil >76 T). The quest for evenhigher fields will increase our understanding of effects that limit coil-operation and thus, apart fromproviding users with higher fields, result also in more reliable coils for fields in the 60 T region. As afirst step in this approach we made a copy of the successful 79 T record coil (copper-stainless-steel-zylon) with the aim to use it as a 75 T user coil. This coil was successfully tested to fields above 65 Tbut further testing had to be postponed in order to avoid excessive coil heating. The actual capacitorbank is optimised for long pulses and thus not well adapted to the highest fields where one needs tohave rather short pulse times in order to reduce heating. In the long term we have planned to install a3 MJ short-pulse capacitor bank but for the time being we have to work with ad hoc modifications ofthe existing 14 MJ bank. After receiving the parts for this modification we expect to test and use thiscoil at field above 70 T in the beginning of 2008.

OutlookThe "groupe bobines" is expanding successfully. The implication of new technical staff in coilbuilding proved to be a big success in terms of quality and quantity. Regular meetings allow theproblems occurring for different coils to be analysed in a broader forum. For the coming year themilestones will be the operation of the split-coil, the production and operation of a new duo-coilsystem (in the framework of the DENUF project) and the availability of user coil s at the 70 T level. Atthe same time we will work on improvement of actual coils mainly on the cooling time and onreduction of the (magnetic) noise during the pulse.


- 46 -

Generator

Personnel involved:

Permanent: DRIGO Loic, FRINGS Paul, GRIFFE Bertrand

GeneralIn order to professionalize the use and maintenance of the capacitor bank we obtained a professionalsoftware package (SEE, electrical expert) to make professional drawings of the electrical installationand all the connections. Previously all wiring diagrams were drawn by hand and this caused archivingand documentation problems.

The 14 MJ capacitor bank

The 14 MJ capacitor bank functioned without any major problems. The only incident was a firing unitin the thyristor stack of module 1 that failed due to a bad contact. Unfortunately this type of problemscannot always be detected by the controlling system before major damage arrives. At a high voltagepulse one thyristor did not fire during this fault resulting in the total voltage being over only one(instead of 12) thyristor. This caused loss of that thyristor as well as the varistor parallel to it. Module1 had to be taken out of service without any influence on the measurement programme since most ofthe coils do not need all the ten modules. For testing a 75 T coil we were limited by the long pulse-time of the capacitor bank and the resulting excessive heating of the coil. For the time being thisproblem can only be partly reduced by modifying the bank ad hoc by removing a (painfully) by hand60 % of the (600!) capacitors.The control software is working routinely and the logging of pulses has been extended to theresistance value of the coil just before and after the pulse.A high-voltage coaxial conductor is replacing the electrical high-voltage connection to the coil inevery cell. Using a coaxial conductor instead of copper strips is more flexible and moreover theconnections are automatically isolated. The decentralised shunts in every cell are at the same timereplaced by a central shunt in the basement.

The "pneumatic" relaysA big improvement was the installation in every box of the so-called "pneumatic relay" which replacesthe HV Ross-relay. The advantage of the new system is that due to the "unlimited" number of contactsthe coil resistance measurements can be performed in a real four-wire mode. Moreover the electricaland the annoying acoustical noise of the Ross-relay are avoided by installing of the new system.

The transportable 150 kJ bank and its upgrade to 1 MJThe transportable 150 kJ bank has proven its usefulness. It is frequently transported between Toulouse,Paris and Grenoble. The frequent mounting and dismounting caused some minor (but annoying)mechanical problems to show up. It is foreseen to build a new and upgraded (1 MJ) capacitor bankwere these problems will be solved. The parts for the new capacitor bank have arrived and assemblingis planned for the first two months of 2008.

LNCMP Annual report 2007

- 47 -

OutlookThe most important and urgent investment is amoderately sized (~3 MJ) capacitor bank witha short pulse. This equipment will permit us toenergise coils in the 80 T range withoutmaking comprises in the design. The requestfor this investment was honoured in the "PlanRegion", unfortunately the university decidedto postpone the actual investment to thesecond investment round.In order to adapt the current 14 MJ slow bankas well as possible to higher field coils we willinstall new (more resistive) crowbarresistances in the beginning of 2008. Amodification of the modules in order to switchwithout loosing too much time between 100%and 40% capacitors is considered. But all thiseffort will result in a bank that is onlyborderline suitable to achieve fields of 75 T orhigher. So a new rapid capacitor bank remains the highest priority.In view of the increased amount of outside users it becomes important to make the installation "fool proof"and also (even more) user friendly. It is planned to modify the software in such a way that a user can onlymake allowed pulses based on the characteristics of the coil and the actual coil temperature (resistance). Atthe same time the user interface will be extended in order to include, for instance, various pumps and theliquid nitrogen filling. Since coils sometimes rapidly change boxes it would be desirable to have anautomatic identification (RFID) system attached to every coil to avoid that the whole logging systemdepends too strongly on the discipline of the users and responsible for the experimental equipment.In order to more successfully investigate problems with coils or with the generator we have foreseen tomeasure the current and voltage of every pulse real-time in a centralised way. These data will be stored onthe computer of the capacitor bank and will provide valuable (historical) information in case of problems.

The new, high energy density, capacitors and an industrialfuse for the 1 MJ upgrade of the transportable capacitorbank.

One of the new, pneumatically driven, relais.


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Single turn installation

Personnel involved:

Permanent: O. Portugall, F. Durantel, L. Bendichou, T. Schiavo, J.P. Laurent

Non permanent: S. Hansel

Installation of the Faraday Cage

The lion’s share of our activity is directed at the completion of a high frequency faraday cage surroundingthe capacitor bank and experimental chambers of the single turn coil Megagauss magnetic field generator.The cage serves several purposes, the protection of personnel and material from accidental discharges, itprovides the working frame of the experimental installation inside and finally it attenuates the anticipatedelectromagnetic noise that is generated at the discharges down to the world’s best signal to noise ratio insingle turn coil experiments.

To achieve structural stability as well as good electromagnetic screening large plates of a honeycombstructure of Aluminium were installed into a structure formed by aluminium profiles. The base of the cage isformed on the same profiles with anti-glide structured solid aluminium plates. Special adjustments weremade to support the steel doors that have been brought from Berlin during the transfer of the machine andhave been framed with steel supports made in-house.

We are aiming to meet or surpass the signal to noise ratio previously achieved at the Berlin installation withthe same setup. Special care has to be taken for the joints of the different panels or frames. The solutionfound was connecting panels by profiles with a wire mesh of aluminium guaranteeing the electrical contact.The figure below shows the original noise level as generated by the discharge (upper curve) and the samerecording with a Faraday cage. The latter curve is amplified by a factor of 50. (Results were taken in Berlin.)Several additional features were installed such as a low pass power line filter to avoid feedback on thebuilding’s power grid. Ventilation and electrical systems have been installed complying with the requirementof the electrical screening. Several guides for non-metallic connections of the inside and outside of the cage,such as optical fibers, gas tubings or vacuum mounts have been added to the cage above each door to providemaximum flexibility for future experimental applications.


- 49 -

Installation of the GeneratorThe single turn coil Megagauss magnetic field generator (schematic below) is being installed into the newlyconstructed Faraday cage. Using know-how and material imported from Berlin it was installed with onlyminor adjustments to meet the spatial requirements of LNCMP.

When completed the available fields will operate on a µs timescale and can surpass 300T. Sample fields aregiven on the viewgraph below. This represents currently the best performance of any such system in theworld; We can deliver higher field at same diameter or same field at higher diameter than the competitorsISSP or NHMFL, respectively. To meet that requirement a 225kJ/60kV capacitor bank is discharged into alightweight disposable coil typically made from sheet copper. The overall inductance determines the field. Ithas been reduced beyond the competitor’s values by using the stripline technique rather than coaxial cablesto transfer the current into the coil. Moreover, the system of Toulouse will allow the use of bath cryostats asthe bore is vertical.

Outlook

The completion of the capacitor bank should take place on a very short timescale now. Previously existingexperimental setups will follow suit in quick succession. Simultaneously a solution for cryogenics will beinstalled.


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User facility activities

Personnel involved:

Permanent : H. Rakoto (coordinator)___________________________________________________________________________________

The LNCMP is a member of a network of European laboratories named EuroMagNET producing highmagnetic field. This network includes three main large infrastructures of high static and pulsed magnetic fields : HFMLat Nijmegen (the Netherlands) for DC field, LNCMP at Toulouse (France) and HLD, Rosendorf-Dresden (Germany)for pulsed field and a number of smaller pulsed-field installations (LVSM, Leuven, Belgium, LCMIZ, Zaragoza,Spainand IFW, Dresden, Germany). EuroMagNET is a consortium organised as Integrated Infrastructure Initiative (I3)concerning research in high magnetic fields and is partially financed under the 6th Framework " Structuring theEuropean Research Area, Research Infrastructures Action ". Details on this network can be seen in the EuroMagNETwebsite (http://www.euromagnet.org).

The Laboratoire National des Champs Magnétiques Pulsés of Toulouse is open to the French and internationalscientific communities and can operate many magnet sites on which various types of experimental set-ups are available.The detailed description of these installations can be found on our web site (www.lncmp.org).

The list below recall the different types of magnets which can be connected to the 14 MJ capacitors bankwhich has the particularity of to be modular, and consequently can be adapted to each type of magnet coil.

Energy(MJ)

Maximum field (T) Useful diameter(B mm)

Rise time / Totaltime (s)

Frequency of shot

1.25 40 19 0.09 / 0.8 1 / hour1.2 62 11 0.025 / 0.150 1 / hour3.3 62 19 0.045 / 0.250 1 / 3 hours8 77

(coilin-coilex)10 Coilin 0.005

Coilex 0.31/ 4 hours

According to the pulse duration, the in-house scientists and the technical staff have developed differentexperimental set-ups, able to perform measurements like ac or dc Transport, Magnetisation or Optical measurements inrelatively extreme limit of temperature (down to 50 mK) or under pressure (up to 2 GPa). Technical developments arealso done in collaboration with the external users (project of NMR, 10 Gpa pressure…). All of these set-ups areavailable for the visitors.

The access to the pulsed field installation and the scientific infrastructure around it, requires a submission ofproposals (twice a year), which are distributed in four scientific themes as Magnetism, Semiconductors, Metals andSuperconductors or Magnetic Resonance and Others. These applications are evaluated by an independent externalprogramme committee on their scientific merit and feasibility. For each evaluated and approved proposal a local contactis appointed to assist the external user.

For the two sessions of 2007, a total number of 70 applications have been submitted and 69 accepted (cf.listedbelow) coming from in-house and external users. The experiments are scheduled in general from April to October forthe first session and from November until the end of March of the following year for the second one.The repartition of these proposals by scientific theme is the following:

- Magnetism: 10- Semiconductors: 24- Metals and Superconductors: 28- Magnetic Resonance and Others: 8

About 75.7 % of these applications come from external users, of wich 11.3 % from French laboratories and therest from other European or international laboratories (see the list below).

We report the evolution of the number of the applications from 2002 to 2007 as well as the distribution percountry:

http://www.hfml.science.ru.nl/

http://www.hfml.science.ru.nl/

http://www.lncmp.org/

http://www.fzd.de/hld

http://www.fys.kuleuven.ac.be/vsm/pf/index.html

http://www.unizar.es/icma/depart/depart6.htm

http://www.ifw-dresden.de/eindex.htm

http://www.euromagnet.org/



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Number of proposals

25

6055

59

70

11

42 43

65

52 53

36

3026

75

2002 (1/2) 2003 2004 2005 2006 2007

Total External user User TNA

Distribution of proposals per country (2002-2007)

17

163

811

13853

245

12

61

45

128

113

922

1

0 20 40 60 80 100 120 140 160

AustriaBelarusBelgium

BrazilCanada

ChinaCuba

FranceGermany

IrelandIsraelItalia

JapanKorea

NetherlandsNorw ay

PolandPortugalRomania

RussiaSw itzerland

U.KU.S.ASpain

Venezuela

Since 2005, applicants coming from European Community laboratories or from associated countries (Bulgaria,Iceland, Israel, Liechtenstein, Norway, Romania, Switzerland), could be reimbursed for their travel and subsistence fees,thanks to the European Community Transnational Access (TNA) contract, part of the Integrated Infrastructure Initiative- EuroMagNET. For the two sessions of 2007, roughly 50% of the external users (26 over 53) have benefitted willbenefit from this financial support.

The proposals submitted to LNCMP is listed below and presented in the following form: Title , Affiliation andApplicant name ( Title * correspond to the proposals submitted during the second session ).


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List of proposals (2007)

Magnetism

1. Study of positive linear magnetoresistance in ferromagnetic materials.Tel Aviv University , Ramat Aviv, 69978 Tel Aviv, IsraëlProf. Alexander Gerber

2. Crystal field, electron structure and magnetic properties in a high magnetic field of Tb:YBa2Cu3Ox

(x = 6.0, 6.4) crystalsLaboratory of Problems for Magnetism, Department of Physics, Moscow State University, RussiaDr. Zoia Kazei

3. Study of magnetization in manganese multiferroics Eu1-xYxMnO3 in high magnetic fieldsA.M. Prokhorov General Physics Institute of Russian Academy of Science, Moscow, RussiaDr. Alexander A. Mukhin

4. FIR study of spin excitations and phase transitions in Eu1-xYxMnO3 multiferroics under high magnetic fieldsA.M. Prokhorov General Physics Institute of Russian Academy of Science, Moscow, RussiaDr Alexander A. Mukhin

5. Anomalous magnetocaloric effect in the rare-earth compound HoVO4 near the energy level crossingLaboratory of Problems for Magnetism, Department of Physics, Moscow State University, RussiaDr. Zoia Kazei

6. High Field Electron Spin Resonance in the nonanuclear complex [Ni(II)9L10(u2-OH)2(u3-OH)2(u-OH2)2(H2O)6](ClO4)4 12.5 MeCN*H2OLeibniz Institute for Solid State and Materials Research IFW, Dresden, GermanyDr. Vladislav Kataev

7. Determination of IRM (Isothermal Remanent Magnetization) anisotropy in 2500 Ma old rock samplesLMTG ,Toulouse, FranceProf. Jean-Luc Bouchez

8. B-T phase diagram of cuprous ferrite CuFeO2 *European Synchrotron Radiation Facility, Grenoble, FranceDr. Cornelius Strohm

9. Reversal of Exchange bias with a large magnetic field *CEA SPEC, Gif sur Yvette, FranceDr. Michel Viret

10. Magnetotransport under high pressure on DWCNTs filled with Fe nanowires *LNCMP, Toulouse, FranceProf. Jean Marc Broto

Semiconductors

11. High magnetic field study of layered InSe under pressureDepartamento de fisica aplicada, University of Valencia, Burjassot, SpainProf. Alfredo Segura

12. Cyclotron-Resonance-monitored Xl—Xt valley crossover in AlP/GaP quantum wellsInstitute of Physics, Humboldt University Berlin, GermanyDr. W. Masselink – Dr. M. P. Semtsiv

13. Strain/Confinement-controlled ground state degeneracy in AlP/GaP QWs monitored by Shubnikov de HassmeasurementsInstitute of Physics, Humboldt University Berlin, GermanyDr. W. Masselink – Dr. M. P. Semtsiv


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14. Electrical transport and magnetoresistance in self-assembled monolayers of aligned carbon nanotubes and in thelayers with intertube bridgingDepartment of Materials Science and Engineering ,Suny at Stony Brook, NY, USA andDepartment of Physics, Belarus State University, Minsk, BelarusDr. Vladimir Samuilov

15. Optically Detected Resonance excited by THz Quantum Cascade LasersLNCMP, Toulouse, FranceProfs. Jean Léotin and Michel Goiran

16. Magnetic Field Dependent Photoluminescence of PentaceneInstitut für Physik, Humboldt-Universität zu Berlin, GermanyDr. Norbert Koch

17. New test for mass enhancement in electron gas of Si-(111) MOSFET *Institute of Solid State Physics Russian Academy of Sciences, Chernogolovka, Moscow, RussiaProf. Valeri T. Dolgopolov

18. Cyclotron resonance of two-dimensional holes in InGaAs/GaAs QW heterostructures in high magnetic fields *Institute for Physics of Microstructures of Russian Academy of Sciences, Nizhny Novgorod, RussiaProf. Vladimir Gavrilenko

19. High field spectroscopy of epitaxial graphene layers *Grenoble High Magnetic Field Laboratory, FranceDr Paulina Plochocka

20. Magneto-photoluminescence of GaAs:Er,O *Molecular Photoscience Research Center, Kobe University, JapanProf. Hitoshi Ohta

21. Lowest Landau level transport-spectroscopy in the Quantum-Hall regime in graphene *Centre on for Research on Adaptive Nanostructures and Nanodevices / Trinity College DublinDr. Vojislav Krstić

22. High magnetic field photoluminescence of p-type InSe *Departamento de fisica aplicada, University of Valencia, Burjassot, SpainProf. Alfredo Segura

23. Magneto-spectroscopy of organic quantum dots *LNCMP, Toulouse, FranceDr. Gerardus Rikken

24. Electrical transport and magnetoresistance in the arrays of metal and metal-oxides nanoclustters *Department of Physics, Belarus State University, Minsk, BelarusDr. Vitaly Ksenevich

25. Cyclotron resonance studies on organic single crystals with high charge carrier mobilities *Stuttgart University, GermanyDr. Jens Pflaum

26. Magnetic field dependence of the exciton dynamics in the organic donator/acceptor system Anthracene:PMDA(pyromellitic dianhydride) *Stuttgart University, GermanyDr. Jens Pflaum

27. Magnetic Field Dependent Photoluminescence of Pentacene (extension) *Institut für Physik, Humboldt-Universität zu Berlin, GermanyDr. Norbert Koch


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28. The magnetic field dependence of triplet-doublet interaction in the organic donator/acceptor systemAnthracene:PMDA (pyromellitic dianhydride) *Stuttgart University, GermanyDr. Jens Pflaum

29. Magnetoresistance of AlP quantum wells under parallel magnetic field *CEMES/CNRS, Toulouse, FranceProf. Alfred Gold

30. InducedΓ-X conduction band crossover in InGaP/GaP nanostructures under hydrostatic pressure in magneticfield *Institute of Physics, Humboldt University Berlin, GermanyDr. Fariba Hatami

31. Magnetic field inducedΓ-X conduction band crossover in InP nanostructures embedded in GaP *Institute of Physics, Humboldt University Berlin, GermanyDr. Fariba Hatami

32. Landau level sequence in graphene *LNCMP, Toulouse, FranceDr. Walter Escoffier

33. Photo-conductivity under 60T on individual carbon nanotubes *LNCMP, Toulouse, FranceProf. Bertrand Raquet

34. Optical properties of carbon nanotubes in organic solutions *Physics Department, Oxford University, UKProf. RobinJ. Nicholas

Metals and Superconductors

35. Characteristics of superconducting permanent magnetsCRISMAT - CNRS UMR 6508, ENSICAEN, Caen, FranceDr. Jacques Noudem

36. Dynamics of magnetic flux trapping in YBCO single domains under pulsed magnetization conditionsCRETA – CNRS, Grenoble , FranceDr. Xavier Chaud

37. Fermi Surface study of the quasi-two-dimensional organic (super)conductors β''-(BEDT-TTF)4A[M(C2O4)3]•Solv (A = NH4, H3O, K; M = Cr, Fe, Ga; Solv = benzonitrile, nitrobenzene, pyridine,dimethylformamide)ICREA, Barcelona / ICMAB-CSIC, SpainDr. Laukhin Vladimir

38. Tests up to 2 GPa of a pressure cell designed for isothermal transport measurements at liquid helium temperaturesin 55 T pulsed magnetic fields. Application to the organic metal (BEDT-TTF)8Hg4Cl12(C6H5Br).LNCMP, Toulouse, FranceDr. Alain Audouard

39. Nernst effect in a quasi-2D organic conductorLNCMP, Toulouse, FranceDr. Cyril Proust

40. Search for criticality in the quasi-one-dimensional cuprate PrBa2Cu4O8

H. H. Wills Physics Laboratory, University of Bristol, UK


- 55 -

Prof. Nigel Hussey

41. Electronic transport in semi-metallic bismuthESPCI & CNRS, Paris, FranceDr. Kamran Behnia

42. Suppression of superconducting fluctuations by high magnetic fields in high-Tc cupratesCEA – SPEC , CE Saclay, Gif-sur-Yvette, FranceDr Florence Rullier-Albenque

43. Investigation of the low temperature normal state of the underdoped Bi2Sr2Ca1Co2O8+δby pulsed high magneticfieldEPFL, Lausanne, SwitzerlandProf. László Forró

44. Transport measurement on single-wall and multi-wall carbon nanotubes at very low temperature and highmagnetic fieldLNCMP, Toulouse, FranceDr. Walter Escoffier

45. Photo-conductivity under 60T on individual carbon nanotubesLNCMP, Toulouse, FranceProf. bertrand Raquet

46. Mesoscopic transport in DWCNTsLNCMP, Toulouse, FranceProf. bertrand Raquet

47. Magneto-transport measurement in the heavy Fermion CeCoIn5LNCMP, Toulouse, FranceDr. David Vignolles

48. High-field Hall effect in YBCOUniversité de Sherbrooke, CanadaProf. Louis Taillefer

49. Fermi Surface study of the quasi-two-dimensional organic (super)conductors *''-(BEDT-TTF)4A[M(C2O4)3]•Solv (A = NH4, H3O, K; M = Cr, Fe, Ga; Solv = benzonitrile, dichlorobenzene,pyridine, dimethylformamide) - (extension)ICREA, Barcelona / ICMAB-CSIC, SpainDr. Laukhin Vladimir

50. Suppression of superconducting fluctuations by high magnetic fields in high-Tc cuprates * - (extension)CEA – SPEC , CE Saclay, Gif-sur-Yvette, FranceDr. Florence Rullier-Albenque

51. High-field Hall effect in YBCO * - (extension)Université de Sherbrooke, CanadaProf. Louis Taillefer

52. Electronic transport in semi-metallic bismuth * - (extension)ESPCI & CNRS, Paris, FranceDr. Kamran Behnia

53. Shubnikov-de Haas oscillations in high temperature superconductors *H. H. Wills Physics Laboratory, University of Bristol, UKProf. Nigel Hussey


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54. Investigation of the low temperature normal state of the underdoped Bi2Sr2Ca1Co2O8+δby pulsed high magnetic *field - (extension)EPFL, Lausanne, SwitzerlandProf. László Forró

55. Shubnikov de Haas effect in misfit cobaltites *Laboratoire Crismat, Caen , FranceDr. Sylvie Hébert

56. dHva experiment in heavy fermions in extreme conditions of temperature and magnetic field *LNCMP, Toulouse, FranceDr. David Vignolles

57. High field ultrasound measurements in the ultra-quantum limit of Bismuth *LNCMP, Toulouse, FranceDr. Cyril Proust

58. Attempt to measure Nernst effect up to the highest fields available (60 T) at low temperature (1.5 K) *LNCMP, Toulouse, FranceDr. Baptiste Vignolle

59. Landau states and electronic conductivity in MWCNTs under 60 T * - (extension)LNCMP, Toulouse, FranceProf. Bertrand Raquet

60. Magnetization and magnetostriction under pulsed magnetic fields of some heavy-fermions compounds *FZK Karlsruhe, Germany - LNCMP, Toulouse, FranceDr. William Knafo

61. High-field phase diagram of the “green phase” system Y2BaCuO5 *FZK Karlsruhe, Germany - LNCMP, Toulouse, FranceDr. William Knafo

62. Ca3Ru2O7: Magnetotransport in the quantum limit *School of Physics & Astronomy, University of St Andrews , UKProf. Andy Mackenzie

Magnetic Resonance and Others

63. Ruby luminescence under high pressure and high magnetic fieldLNCMP, Toulouse, FranceProf. Jean Marc Broto

64. Pulsed field NMR on high Tc superconductorsFaculty of Physics and Earth Science, University of Leipzig, GermanyDr. Juergen Haase

65. Cyclotron resonance experiments in novel semiconductor dilute nitride alloys *University of Nottingham, UKDr. Amalia Patanè

66. Pulsed field NMR on cuprate and cobaltate superconductors * - (extension)Faculty of Physics and Earth Science, University of Leipzig, GermanyDr. Juergen Haase

67. Absorption measurements on aligned films of DNA-wrapped carbon nanotubes *


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Department of Electrical and Computer Engineering, Rice University, Houston , USAProf. Junichiro Kono

68. Investigation of the dynamic alignment of DNA-wrapped carbon nanotubes in liquid suspension * - (extension)Department of Electrical and Computer Engineering, Rice University, Houston , USAProf. Junichiro Kono

69. Ruby luminescence under high pressure and high magnetic field * - (extension)LNCMP, Toulouse, FranceProf. Jean Marc Broto

70. Installation of a new sample stick design and first ODMR experimentsKU Leuven – INPAC, BelgiumProf. Victor V. Moshchalkov.


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PUBLICATIONS 2007

Articles dans des revues avec comité de lecture (ACL) :

1

Bangura A.F, J. D. Fletcher, A. Carrington, J. Levallois, M. Nardone, B. Vignolle, P. J.Heard, N. Doiron-Leyraud, D. LeBoeuf, L. Taillefer, S. Adachi, C. Proust and N. E. Hussey.“Shubnikov-de Haas oscillations in YBa2Cu4O8”.Physical Review Letters, accepted for publication

2Banks M. G., Heidrich-Meisner F., Honecker A., Rakoto H., Broto J-M, Kremer R. K. Highfield magnetization of the frustrated one-dimensional quantum antiferromagnet LiCuVO4.Journal of Physics-Condensed Matter 19, 145227 (2007)

3

Battesti R., B. Pinto Da Souza, S. Batut, C. Robilliard, G. Bailly, C. Michel, M. Nardone, L.Pinard, O. Portugall, G. Trénec, J.-M. Mackowski, G.L.J.A. Rikken, J. Vigué, and C. RizzoThe BMV experiment: a novel apparatus to study the propagation of light in a transversemagnetic field.European Physical Journal D (2007) DOI: 10.1140/epjd/e2007-00306-3

4

Cadenas Ruben, Perez Flor V., Quintero Miguel, Quintero Eugenio, Tovar Rafael,Morocoima Manuel, Gonzalez Jesus, Bocaranda P., Ruiz J., Broto J. M., Rakoto H.Magnetic properties of the semimagnetic semiconductor Zn0.15Mn0.85Ga2Se4.Physica B-Condensed Matter 389, 302 (2007)

5

Doiron-Leyraud Nicolas, Cyril Proust, David LeBoeuf, Julien Levallois, Jean-BaptisteBonnemaison, Ruixing Liang, D. A. Bonn, W. N. Hardy & Louis Taillefer."Quantum oscillations and the Fermi surface in an underdoped high-Tc superconductor".Nature 447,565-568 (2007)

6

Drechsler S.-L., Richter J., Kuzian R, Malek J., Tristan N., Buechner B., Moskvin A. S.,Gippius A. A., Vasiliev A., Volkova O., Prokofiev A., Rakoto H., Broto J. -M., Schnelle W.,Schmitt M., Ormeci A., Loison C., Rosner H.Helimagnetism and weak ferromagnetism in edge-shared chain cuprates.Journal of Magnetism and Magnetic Materials 316, 306 (2007)

7Essaleh L., Wasim Syed M., Galibert J.Effect of a high magnetic field on the localization length in n-type copper indium diselenide.Comptes Rendus Physique 8, 942 (2007)

8

Ferrando V., I. Pallecchi; C. Tarantini, D. Marre, M. Putti, C. Ferdeghini, F. Gatti, HU.Aebersold, E. Lehmann, E. Haanappel, I. Sheikin, P. Orgiani, and X.X. Xi.Systematic study of disorder induced by neutron irradiation in MgB2 thin films .Journal of Applied Physics 101, 043903, (2007).

9Gerber A., I. Kishon, I.Ya. Korenblit, O. Riss, A. Segal, M. Karpovski, B. Raquet. Linearpositive magnetoresistance and quantum interference in ferromagnetic metals.Physical Review Letters. 99, 027201 (2007)

10Goiran M, Klingeler R, Kazei ZA, Snegirev, V. V. Microwave absorption in the singletparamagnet HoVO4 in high pulsed magnetic fields up to 40T.Journal of Magnetisme and Magnetic Materials 318, 1 (2007).

11Gonzalez J., Power Ch., Belandria E., Broto J. M., Puech P., Sloan J., Flahaut E. Pressuredependence of Raman modes in DWCNT filled with PbI2 semiconductor. Physica StatusSolidi B-Basic Solid State Physics 244 (1): 136-141 (2007)

12

Guyot H., J.Dumas, M. Kartsovnik, J. Marcus, C. Schlenker, I. Sheikin, D. Vignolles.Angular studies of the magnetoresistane in the density wave state of the quasi two-dimensional purple bronze KMo6O17.European Physical Journal B 58, 25 (2007)


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13

Herranz G., Basletic M., Bibes M., Carretero C., Tafra E., Jacquet E., Bouzehouane K.,Deranlot C., Hamzic A., Broto J.-M., Barthelemy,A., Fert, A.High mobility in LaAlO3/SrTiO3 heterostructures: Origin, dimensionality, and perspectives.Physical Review Letters 98, 216803 (2007)

14

Kim J. S., Xie Wenhui, Kremer R. K., Babizhetskyy V., Jepsen O., Simon A., Ahn K. S.,Raquet B., Rakoto H., Broto J.-M., Ouladdiaf B.Strong electron-phonon coupling in the rare-earth carbide superconductor La2C3.Physical Review B 76, 014516 (2007)

15

Krstic V, G.L.J.A. Rikken, P. Bernier, S. Roth and M. Glerup,"Nitrogen doping of metallic single-walled carbon nanotubes: n-type conduction and dipolescattering",Europhysics Letters 77, 37001 (2007)

16Krstic V., G.L.J.A. Rikken, M. Kaempgen, S. Roth and J. A. Beukes,Tellurium nanocylinders under pressure: effects of the geometry of nanostructures, AdvancedMaterials 19, 1101 (2007)

17Langford R., M. Thornton, X. Wang, W. Blau, B. Lassagne, B. Raquet. Magnetoresistanceand spin-diffusion in Multi-walled carbon nanotubes.Microelectronic Engineering. 84, 1593 (2007

18

Lassagne B., Cleuziou J.-P., Nanot S., Escoffier W., Avriller R., Roche S., Forro L., RaquetB., Broto J.-M.Aharonov-Bohm conductance modulation in ballistic carbon nanotubes.Physical Review Letters 98 176802 (2007)

19

LeBoeuf David, Nicolas Doiron-Leyraud, Julien Levallois, R. Daou, J.-B. Bonnemaison, N.E. Hussey, L. Balicas, B. J. Ramshaw, Ruixing Liang, D. A. Bonn, W. N. Hardy, S. Adachi,Cyril Proust & Louis Taillefer."Electron pockets in the Fermi surface of hole-doped high-Tc superconductors".Nature 450, 533-536 (2007)

20

Mendels P., Bert F., de Vries M. A., Olariu A., Harrison A., Duc F., Trombe J. C., Lord J.S.,Amato A., and Baines C.Quantum magnetism in the paratacamite family: Towards an ideal kagomé lattice . PhysicalReview Letters 98, 077204 (2007).

21

Mendels P., Olariu A., Bert F., Bono D., Limot L., Collin G., Ueland B., Schiffer P., CavaR.J., Blanchard N., Duc F. and Trombe J. C.Spin dynamics in frustrated magnets: from edge- to corner-sharing geometriesJournal of Physics: Condensed Matter 19, 145224 (2007).

22Mortimer I.B, L.J.Li, R.A.Taylor, G.L.J.A.Rikken, O.Portugall, R.J.Nicholas. Magneto-optical studies of single-wall carbon nanotubes.Physical Review B 76, p.085404, (2007)

23Nicholas R.J, I.B.Mortimer, L.J.Li, A.Nish, O.Portugall, G.L.J.A.Rikken.Temperature and magnetic field dependent photoluminescence from carbon nanotubes.International Journal of Modern Physics B 21/8-9 p.1180, (2007)

24

Portugall O, V.Krstic, G.L.J.A.Rikken, J.Kono, J.Shaver, S.Zaric, V.C.Moore, R.H.Hauge,R.E.Smalley, Y.Miyauchi, S.Maruyama.Magneto spectroscopy of single-walled carbon nanotubes.International Journal of Modern Physics B 21/8-9 (2007) p.1189

25Robilliard C., R. Battesti, M. Fouché, J. Mauchain, A.-M. Sautivet, F. Amiranoff, C. Rizzo.No ‘‘Light Shining through aWall’’: Results from a Photoregeneration Experiment.Physical Review Letters 99, 190403 (2007)


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26Rullier-Albenque F., H. Alloul, C. Proust, P. Lejay, A. Forget, and D. Colson. TotalSuppression of Superconductivity by High Magnetic Fields in YBa2Cu3O6.6.Physical Review Letters 99 027003 (2007)

27

Sakarya S., van Dijk N. H., de Visser A., Brueck E., Huang Y., Perenboom J. A. A. J.,Rakoto H., Broto J.-M.High field magnetisation measurements on UIr in the ferromagnetic state.Journal of Magnetism and Magnetic Materials 310, 1564 (2007)

28

Serrate D., De Teresa J.M., Algarabel P.A., Galibert J., Ritter C., Blasco J., Ibarra M.R.Colossal magnetoresistance in CaxSr2-xFeReO6 double pervoskites: evidence for field inducedphase coexistence.Physical Review B 75, 165109 (2007)

29Serrate D., De Teresa J.M., Algarabel P.A., Marquina C., Blasco J., Ibarra M.R. Galibert J.Magnetoelastic coupling in Sr2(Fe1−xCrx)ReO6 double perovskites.Journal of Physics : Condensed Matter 19 436226 (2007)

30

Shaver J, J.Kono, O.Portugall, V.Krstic, G.L.J.A.Rikken, Y.Miyauchi, S.Maruyama,V.Perebeinos.Magnetic brightening of carbon nanotube photoluminescence through symmetry breaking.Nano Letters 7, 1851 (2007)

31

Thilly L., P.O. Renault, S. Van Petegem, S. Brandstetter, B. Schmitt and H. VanSwygenhoven, V. Vidal and F. Lecouturier.Evidence of internal Bauschinger test in nanocomposite wires during in-situ macroscopictensile cycling under synchrotron beam.Applied Physics Letters 90, 241907 (2007)

32Vedeneev S.I., D. K. Maude, E. Haanappel, and V. P. Mineev.c-axis resistivity of La-free Bi2+xSr2-xCuO6+single crystals in high magnetic fields.Physical Review B, 75 (2007) 064512.

33

Vidal V., L. Thilly, F. Lecouturier, P.-O. Renault.Cu nanowhiskers embedded in Nb nanotubes inside a multiscale Cu matrix: the way to reachextreme mechanical properties in high strength conductors.Scripta Materiala , vol 57 245-248 (2007)

34

Vignolles D., A. Audouard, , R. B. Lyubovskii, S. Pesotskii, J. Beard, E. Canadell, G.Shilov, R. Lyubovskaya.Crystal structure, Fermi surface calculations and Shubnikov-de Haas oscillations spectrum ofthe organic metal theta-(BETS)4HgBr4(C6H5Cl) at low temperature.Solid State Sciences 9 1140-1148 (2007)

35

Vignolles D., A. Audouard, V. Laukhin, J. Beard, E. Canadell, N. Spitsina, E. Yabubskii.Frequency combinations in the magnetoresistane oscillations spectrum of a linear chain ofcoupled orbits with a high scattering rate.European Physical Journal B 55, 383-388 (2007)

36C. Detlefs, F. Duc, Z.A. Kazei, J. Vanacken, P. Frings, W. Bras, J.E. Lorenzo, P.C. Canfield,G.L.J.A. Rikken "Direct observation of the high magnetic field effect on the Jahn-Tellerstate in TbVO4", accepted for publication in Phys. Rev. Lett.. arxiv 0711.2874

37Grigorieva, I.V., W. Escoffier, V.R. Misko, B.J. Baelus, F.M. Peeters, L.Y. Vinnikov, S.V.Dubonos, “Pinning induced formation of vortex clusters and giant vortices in mesoscopicsuperconducting disks », Physical Review Letters 99, 147003 (2007)

38

Kataev V, Schaufuss U, Goiran M, Klingeler R, Sekar C, Krabbes G, Tristan N, Waske A,Hess C, Drechsler S.-L, Buechner B.The low-dimensional spin magnet CaCu2O3 probed by high-field.Journal of Magnetism and Magnetic Materials 310, 1251 (2007)


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39

Hawthorn D.G., S.Y. Li, M. Sutherland, E. Boaknin, R.W. Hill, C. Proust, F. Ronning, M.A.Tanatar, J. Paglione, L. Taillefer, D. Peets, R.X. Liang, D. A. Bonn, W.N. Hardy, N.N.Kolesnikov”Doping dependence of the superconducting gap in Tl2Ba2CuO6+from heat transport”Physical Review B 75, 104518 (2007)

40Semtsiv M.P., Dressler S., Masselink W.T., Goiran M., Rylkov V.V., Galibert J., Leotin J.High magnetic field study of 2D electron gas in AlP.International Journal of Modern Physics B 21, 1466 (2007)

41Bert F., Nakamae S., Ladieu F., L’Hôte D., Bonville P., Duc F., Trombe J.-C., & Mendels P.Low temperature magnetization of the S= kagome antiferromagnet ZnCu3(OH)6Cl2Physical Review B 76, 132411 (2007).

42

Olariu A., Mendels P., Bert F., Duc F., Trombe J.-C., M.A. de Vries, and Harrison A.17O NMR study of the intrinsic magnetic susceptibility and spin dynamics of the quantumkagome antiferromagnet ZnCu3(OH)6Cl2accepted for publication in Physical Review Letters., arxiv 0711.2459

43

Girault B., V. Vidal, L. Thilly, P.-O. Renault, P. Goudeau, E. Le Bourhis, P. Villain, J.Tranchant, J.-P. Landesman, P.-Y. Tessier, B. Angleraud, M.-P. Besland, A. Djouadi, F.Lecouturier.Small scale mechanical properties of polycrystalline materials: in situ diffraction studies.Internation Jouran of Nanotechnology «The nanotechnology in C’Nano Nord-Ouest»,accepted for publication

Communications avec Actes (ACT) :

1Chaud X., E. Haanappel, J. G. Noudem and D. Horvath.Trapped field of YBCO single-domain samples using pulse magnetization from 77K to 20K.8th European Conference on Applied Superconductivity (EUCAS 2007)(sous presse)

2

Detlefs C., Frings P., Vanacken J., Duc F., Lorenzo J. E., Nardone M., Billette J., ZitouniA., Bras W. and Rikken G.L.J.A.Synchrotron X-ray Powder Diffraction Studies in Pulsed Magnetic Fields.AIP Conference Proceedings 879, 1695-1698 (2007)

3

Goiran M., Galibert J., Leotin J., Rylkov V.V., Semtsiv M., Bierwagen O., Masselink W.T.A THz niche for AlP/GaP quantum wells. Proc 2007 APS March Meeting, Focus session:« Physics & Technology of III-V Semiconductors in Infrared & THz Imaging II » March 5-9,2007 , Denver Colorado USA

4

Goiran M., Semtsiv M.P., Dressler S., Masselink W.T., Galibert J., Fedorov G., Smirnov D.,Rylkov V. V., Léotin J.Conduction band states in AlP/GaP quantum wells. in Proc 13th Int. Conf Narrow GapSemiconductors « NGS 13 » Guilford UK July 8th 12th, 2007

5Hansel Stefan, Von Ortenberg Michael."Transient Fields on Indium Antimonide and Mercury Cadmium Telluride"; 28th ICPS,Vienna, 22-26 Juliet 2006, AIP Conf. Proc. *893*, 131 (2007)

6

Kataev V.,C. Golze, A. Alfonsov, R. Klingeler,B. Büchner, M Goiran, J-M. Broto, H.Rakoto, C. Mennerich, H-H. Klauss, S. Demeshko, G. Leibeling and F. Meyer. Magnetism ofa novel tetranuclear nickel(II) cluster in strong magnetic fields. YAMADA CONFERENCELX ON RESEARCH IN HIGH MAGNETIC FIELDS, 16–19 Août 2006, Sendai Japan.Journal of Physics : Conference Series, Vol.51, pages 351-354 (2006)


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7

Ksenevich V. K., Galibert J. , Kozlov V, Samuilov V. A.Magnetotransport properties of carbon nanotubes fibers. Proc. Physics, Chemistry andApplications of Nanostructures « NANOMEETING 2007 » Minsk Belarus 22-25 may 2007,ed by V.F. Borisenko, S.V. Gaponenko, V.S. Gurin pp 262

8Semtsiv M. P., Goiran M., Rylkov V., Galibert J., Dressler S., Masselink W. T., Léotin J.Symmetry of the Conduction-band Minima in AlP.AIP Conference Proceedings, vol. 893, pp. 329–330, 2007.

9

Semtsiv M.P , M. Goiran, V. Rylkov, J. Galibert, S. Dressler, W. T. Masselink, J. Léotin.Symmetry of the conduction band minima in AlP.Proceedings of the 28th International conference on the physics of semiconductors, (ICPS-2006), Vienne , 24-28 Juillet 2006

10

Thilly L., V. Vidal, F. Lecouturier.Plasticity mechanisms in multiscale copper-based nanocomposite wires. Thermec’2006(International Conference on Processing & Manufacturing of Advanced Materials), 4-8July2006, Vancouver (Canada).Materials Science Forum, Vols. 539-543 (March 2007), pp814-819

11

Vanacken J., Detlefs C., Mathon O., Frings P., Duc F., Lorenzo J.E., Nardone M., BilletteJ., Zitouni A., Dominguez M.-C., Herczeg J., Bras W., Moshchalkov V. V., and RikkenG.L.J.A.Synchrotron X-ray Powder Diffraction and Absorption. Spectroscopy in Pulsed MagneticFields with Milliseconds Duration.AIP Conference Proceedings 902, 103-106 (2007).

Communications sans Actes (COM) :

1

Aleshkin V Ya, Yu.B.Vasilyev, V.I.Gavrilenko, B.N.Zvonkov, A.V.Ikonnikov, D.V.Kozlov,S.S.Krishtopenko, M.L.Orlov, Yu.G.Sadofyev, K.E.Spirin, M.L.Sadowski, M.Goiran,W.Knap.Cyclotron resonance study of 2D electrons and holes in quantizing magnetic fields. Abst. VIIIRussian Conf. Phys. Semiconductors, September 30 - October 5, 2007, Ekaterinburg, p.194

2

Aronzon B.A, V.V. Rylkov, A.S. Lagutin, V.V. Podolskii, V.P. Lesnikov, M. Goiran, J.Galibert, B. Raquet, J. Léotin.Peculiarities of the transport properties of InMnAs layers in strong magnetic fields.International Conference “Spin Electronics: Novel Physical Phenomenon and Materials”.Tbilisi, Georgia, Oct. 22-24, 2007. Abstracts, p.44-45.

3

Aronzon B.A , V.V. Rylkov, P.A. Pankov, A.B. Davydov, B.N. Zvonkov, Yu.A. Danilov, M.Goiran, B. Raquet, A. Lashkul, R. Laiho.Properties of GaAs/InGaAs/GaAs quantum wells doped with a Mn -layer.International Conference “Spin Electronics: Novel Physical Phenomenon and Materials”.Tbilisi, Georgia, Oct. 22-24, 2007. Abstracts, p.19-20.

4Goiran M.Terahertz spectroscopy under high magnetic field. Journées couplées GDR ondes et GDRTHZ, 5-6 Décembre 2006, Montpellier.

5Goiran M. , J. Galibert, V. Rylkov, J. Léotin, M. P. Semtsiv, S. Dressler, W. T. Masselink.Study of AlP-GaP heterostuctures towards green LED application. JMC 10, Toulouse,Septembre 2006

6

Goiran M., Galibert J., Leotin J., Rylkov V.V., Semtsiv M., Bierwagen O., Masselink W.T.A THz niche for AlP/GaP quantum wells . in Proc 2007 APS March Meeting, Focussession: « Physics & Technology of III-V Semiconductors in Infrared & THz Imaging II »March 5-9, 2007 , Denver Colorado USA


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7Goiran M., M. Costes, J. M. Broto, F. C. Chou , R. Klingeler, E. Arushanov, S.-L.Drechsler, B. Büchner , V. Kataev.High-field ESR studies of the quantum spin magnet CaCu2O3. JMC 10, Toulouse, 2006.

8

Goiran M., Semtsiv M.P., Dressler S., Masselink W.T., Galibert J., Rylkov V.V., Leotin J.THz spectroscopie of the electron subbands in AlP Qws. French Russian seminar « Sourcesand Detectors of TeraHertz radiation based on semiconductor nanostructures. » LNCMPToulouse 5th and 6th June 2007.

9Jaudet C. , D. Vignolles, C. Proust, A. Audouard, J. Flouquet, I. Sheikin, G. Lapertot .Oscillations de Haas-van Alphen dans le composé à fermions lourds CeCoIn5. GDR NEEM àTours 5 au 8 juin 2007

10Jaudet C., D. Vignolles, C. Proust, A. Audouard, J. Flouquet, I. Sheikin, G. Lapertot.Oscillations de Haas-van Alphen dans le composé à fermions lourds CeCoIn5. Congrès SFP,Grenoble 2007

11Jaudet C., D. Vignolles , C. Proust, A Audouard.Systèmes fortement corrélés : diagramme de phase, criticalité et fermiologie. GDR NouveauEtat Electronique de la Matière Gif/Yvette 18-19 décembre 2006.

12

Kozlov D.V, A.V.Ikonnikov, K.E.Spirin, B.N.Zvonkov, V.I.Gavrilenko, W.Knap, M.Goiran.Cyclotron resonance of holes in strained InGaAs/GaAs QW heterostructures in high magneticfields. Proc. 15thInt. Symp. “Nanostructures: Physics and Technology”, Novosibirsk, Russia, June 25-29,2007; Ioffe Institute, St.Petersburg, 2007, pp.28-29 (ISBN 978-5-93634-022-2).

13

Laukhin V., D. Vignolles, A. Audouard, M . Nardone, J. Béard, E. Canadell, T.Prokhorova, E. Yagubskii.Pressure effect on magneto/transport properties of BEDT-TTF based molecular metals withTris(oxale)metalate anions. ISCOM'97: International Symposium on Crystalline OrganicMetals – Spain (September 2007)

14

Orlov M.L , A.V.Ikonnikov, Yu.B.Vasilyev, S.S.Krishtopenko, D.V.Kozlov, V.Ya.Aleshkin,Yu.G.Sadofyev, V.I.Gavrilenko, M.L.Sadowski, W.Knap, M.Goiran, B.N.Zvonkov.Cyclotron resonance of 2D electrons and holes in high magnetic fields. French-RussianSeminar "Sources and detectors of terahertz radiation on semiconductor nanostructures". June5-6, 2007, LNCMP, Toulouse.

15

Thilly L., V. Vidal, P-O Renault, F. Lecouturier, S. Van Petegem, B. Schmitt, H. VanSwygenhoven.Déformation in-situ de composites nanofilamentaires Cu/Nb: effet Bauschinger et stockagedes dislocations. Colloque Plasticité 2007, 19-21 Mars 2007, Futuroscope

16

Thilly L., V. Vidal, P-O Renault, F. Lecouturier, S. Van Petegem, B. Schmitt, H. VanSwygenhoven.Plasticity of nanocomposite wires during in-situ tensile tests under neutrons and X-rays:Bauschinger effect, size effect and dislocation storage. International workshop on small scaleplasticity:, 5-8 september 2007, Braunwald (Switzerland)

17

Vidal V., L. Thilly, F. Lecouturier, P-O Renault, S Van Petegem and H. Van Swygenhoven.High Strength Cu/Nb Nanocomposite Wires Processed by Severe Plastic Deformation:Effects of Size and Composite Structure on Mechanical Properties. MRS 2007( Materials Research Society conference), 26-30 november 2007, Boston (USA)

18

Vidal V., L. Thilly, S. Van Petegem, U. Stuhr, F. Lecouturier, P.O. Renault, H. VanSwygenhoven.Size effect in the plasticity of multiscale nanofilamentary Cu/Nb composite wires during in-situ tensile tests under neutron beam. ECNS 2007 (4th European Conference on NeutronScattering), 25-29 june 2007, Lund (Sweden)


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19

Vidal V., L. Thilly, S. Van Petegem, U. Stuhr, F. Lecouturier, P.O. Renault, H. VanSwygenhoven.Size effect in the plasticity of multiscale nanofilamentary Cu/Nb composite wires during in-situ tensile tests under neutron beam.EUROMAT 2007, 10-13 September 2007, Nurnberg (Germany)

Ouvrages scientifiques (OS) :

1

Lecouturier F., L.Thilly.« Applications of nanomaterials: mechanics : high field coils ». Nanomaterials andnanochemistry, Springer editions, (2007), Lahmani (Marcel) / Bréchignac (Catherine) /Houdy (Philippe). To be published

2

Sandim M., H. R. Z. Sandim, L. Ghivelder L. Thilly, F. Lecouturier, D. Stamopoulos.“Superconductivity and magnetic properties of multifilamentary Cu-Nb micro/nanocomposite wires”. Magnetism and Superconductivity in low dimensional systems: Utilizationin Biotechnological and Engineering Applications, published by NOVA Science, New York(www.novapublishers.com), edited by Dimosthenis Stamopoulos. To be published

Conferences Invitées (INV) :

1Batut S., J. Mauchain, R. Battesti, C. Robilliard, M. Fouché, and O. Portugall.A Transportable Pulsed Magnet System for Fundamental Investigations in QuantumElectrodynamics and Particle Physics. IEEE Transactions on applied superconductivity.

2

Duc F., Chesnel K., Detlefs C, Frings P., Vanacken J., Mathon O., Lorenzo J. E., NardoneM., Billette J., Zitouni A., Bras W. and Rikken G.L.J.A.X-ray powder diffraction and absorption experiments under pulsed magnetic fields up to 30T.E-MRS Fall Meeting 2007, 17-21 Septembre 2007, Varsovie, Pologne.

3

Galibert J« Some aspects of nanophysics in Toulouse » .Conference at Institute for Nuclear Problems Belarus State University, Minsk, Belarus may2007

4Goiran M.Terahertz spectroscopy under high magnetic field. ESRF workshop on “TeraHertz Dynamicsprobed with X-rays”. ESRF, Grenoble, 10-11-12 September 2007.

5

Hansel Stefan, Von Ortenberg Michael, Portugall Oliver, Rikken Geert."The Single Turn Coil Generator, Toulouse / Berlin, a user magnet for EuroMagNET",presentation orale invité, Summer School "Trends in High Magnetic Field Science" 29.8.07-8.9.07 Cargese, France, Ecole d'été Cargese

6

Hansel Stefan, Von Ortenberg Michael, Kirste Alexander, Richter Bettina, PortugallOliver, Rikken Geert, Durantel Florent."MegaGauss @ EuroMagNET", presentation orale invité, EuroMagNET User Meeting,22./23.10.2007 Nijmegen, Pays-Bas

7Latyshev Yu.I 1, A.P. Orlov1, P. Monceau2, Th. Fournier2, E. Mossang3, D. Vignolles4.Enhancement of Peierls transition temperature in NbSe3 by high magnetic field. InternationalSchool, "Magnetic field for science" – Août 2007

8Proust C.« La surface de Fermi des supraconducteurs à haute température critique ». invitation ducomité local de la Société Française de Physique à Toulouse (octobre 2007)

http://www.novapublishers.com/






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9

Proust C., J. Levallois, N. Doiron-Leyraud, , D. LeBoeuf, N.E. Hussey , R. Liang, D.A.Bonn, W.N. Hardy, L. Taillefer, " Fermi surface of underdoped cuprate revealed byquantum oscillations and Hall effect". "Canadian Institute for Advanced Research" meetingof the Quantum Materials Program, Montréal, Canada (octobre 2007)

10

Proust C., N. Doiron-Leyraud, , D. LeBoeuf, J. Levallois, J-B Bonnemaison, R. Liang, D.A.Bonn, W.N. Hardy, Louis Taillefer, "Quantum oscillations and Fermi surface inYBa2Cu3O6.5". "Exploring Quantum Matter: Visions and Opportunities", St Andrews,Ecosse (juillet 2007)

11Raquet B. Aharonov-Bohm conductance modulation in Ballistic Carbon Nanotubes,International Winter School on the Electronic Properties of Novel Materials. IWEPNM2007,Kirchberg – Autriche Mars 2007

12 Rikken G.L.J.ALight scattering in magnetic fields, IMCODE Council meeting, Grenoble 20/12/2007

13 Rikken G.L.J.AMagnetic fields and chirality; 'Chirality at the Nanoscale', Sitges17-21 september 2007

14 Rikken G.L.J.AMagneto-optics and symmetry; EuroMagNET School, Cargèse 27 August-7 september 2007

15 Rikken G.L.J.AMagneto-optics and symmetry; invited to INLN, Nice 14 december 2007

16

Proust C., J. Levallois, N. Doiron-Leyraud, , D. LeBoeuf, N.E. Hussey , R.Liang, D.A.Bonn, W.N. Hardy, L. Taillefer.Fermi surface of underdoped cuprate revealed by quantum oscillations and Hall effect,invited to the workshop on Properties on High Tc superconductors, Munich, 17-18 dec 2007

17

Levallois J. , N. Doiron-Leyraud, Proust C., D. LeBoeuf, J-B Bonnemaison, R. Liang, D.A.Bonn, W.N. Hardy, Louis Taillefer."Surface de Fermi révélée par des oscillations quantiques dans YBa2Cu306.5""GDR NEEM, Tours 5 au 8 juin 2007"

18

Levallois J., Proust C., N. Doiron-Leyraud , D. LeBoeuf, N.E. Hussey , R. Liang, D.A.Bonn, W.N. Hardy, L. Taillefer."Quantum oscillations and the Fermi surface in underdoped high-Tc superconductors""EuroMagNET Summer School, Cargèse 27 August-7 september 2007"

Evolution of the scientific production of the LNCMP


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Organisation 1/1/2008

email adresses : “first 8 letters of family name”@lncmp.org, e.g. [email protected]. For telephone numbers, consultwww.lncmp.org.

Director G.Rikken DRDeputy O. Portugall IR

Generator-ElectronicsP. Frings IRB. Griffe AIL. Drigo IE

Reinforced conductorsF. Lecouturier IRN. Ferreira AJTJ.M Lagarrigue TM. Mainson CDDCoilsP. Frings IRJ. Billette IEF. Giquel TJ. Béard CDD

ScientistsA. Audouard CRR. Battesti MC UPSJ.M. Broto PR UPSF. Duc CRW. Escoffier MC INSAJ. Galibert CRM. Goiran PR UPSE. Haanappel CRW. Knafo CRJ. Léotin PR UPS emeritusC. Proust CRB. Raquet PR INSAL. Rigal MC UPSD. Vignolles MC INSA

General SupportH. Rakoto IRG. Gauran AIF. Durantel IES. George TL. Bosseaux T

Machine shopG. Coffe AI INSAL. Bendichou TT. Schiavo AJT UPS

Administration / SecretaryS. Bories AJT INSAF. Mateo T

PhD StudentsS. Batut INSAJ. Levallois UPSC. Jaudet UPSCh. Power (UPS/Merida)E. Bellandria (UPS/Merida)S. Nanot CNRSM. Millot UPSJ.B. Dubois (Poitiers)

Cryogenics-Pressure-VacuumM. Nardone IRA. Zitouni CDDJ.P. Laurent T INSA

PostdocsS. HanselF. BielsaB. Vignolle

mailto:�first 8 letters of family name�@lncmp.org

mailto:[email protected]


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