Magnetism of the regular and excess iron in Fe1+xTe studied by Mössbauer spectroscopy

A. Błachowski1, K. Ruebenbauer1, P. Zajdel2, E.E. Rodriguez3, M.A. Green3, 4

1Mössbauer Spectroscopy Division, Institute of Physics, Pedagogical University, Kraków, Poland

2Division of Physics of Crystals, Institute of Physics, Silesian University, Katowice, Poland

3National Institute of Standards and Technology, Center for Neutron Research, Gaithersburg, U.S.A.

4Department of Materials Science and Engineering, University of Maryland, U.S.A.---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------

XVI National Conference on Superconductivity, 7-12 October 2013, Zakopane, Poland

Tsc max = 56 K 47 K 18 K 14 K

37 K at 9 GPa

Fe-based Superconducting Familiespnictogens: P, As, Sb chalcogens: S, Se, Te

1111 122 111 11

LnO(F)FeAs AFe2As2 AFeAs FeTe(Se,S)

Ln = La, Ce, Pr, Nd, Sm, Gd … A = Ca, Sr, Ba, Eu, K A = Li , Na

Layered Structure of Fe-based Superconductors

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Spin density wave (SDW)

magnetic order

perpendicular

longitudinal

COMMENSURATE

or INCOMMENSURATE

Fe1+xTe BaFe2As2

Spin density wave (SDW) seen by Mössbauer Spectroscopy

] )12( sin[ )(1

12

N

nn qxnhqxB

h2n-1 – amplitudes of subsequent harmonics

q – wave number of SDW x – relative position of the resonant nucleus along propagation direction of SDW

SDW hyperfine field distribution 57Fe Mössbauer spectrum

Fe1+xTe

x = 0.04 – 0.18x = 0.06 , 0.10 , 0.14 , 0.18

Magnetic-crystallographic phase diagramS. Röler et al., Phys. Rev. B 84 174506 (2011)

x in Fe1+xTe

G.F. Chen et al., Phys. Rev. B 79 140509(R) (2009)

Parent CompoundFe1+yTe

Doped Compound → Superconductory ≈ 0

Fe1+yTe1-xSex Fe1+yTe1-xSx

K. Katayama et al., J. Phys. Soc. Japan 79, 113702 (2010)

Y. Mizuguchi et al., J. Appl. Phys. 109, 013914 (2011)

Alcoholic beverages induce superconductivity in FeTe1−xSx

K. Deguchi et al., Supercond. Sci. Technol. 24, 055008 (2011)

”Some components present in alcoholic beverages, other than water and ethanol, have the ability to induce superconductivity in FeTe0.8S0.2 compound.”

Fe1.06Te 57Fe Mössbauer spectra SDW field distribution shape of SDW

                                                                     regular (tetrahedral) Fe          excess (interstitial) Fe SDW higher magnetic fields than SDW

Fe1.14Te

57Fe Mössbauer spectra  SDW field distribution shape of SDW

  Three different kinds (surroundings) of excess (interstitial) Fe.

Magnetism of the excess Fe and SDW disappear at the same transition temperature.

SDWregular Fe

Fe1+xTe

x=0.06

x=0.10

x=0.14

x=0.18

65 K 4.2 Kshape of SDW

at 4.2 K

SDW is very sensitive to concentration of interstitial iron with relatively large localized magnetic moments.

regular Fe (SDW) excess Fe                                                    

Root mean square amplitude of SDW versus temperature

The critical exponent of the mean square amplitude of SDW versus temperature indicates that the universality class is close to the (1, 2) class,

i.e. the one dimension of the spin space (Ising model) and two spatial dimensions (Fe-Te layers).

Conclusions

Excess (interstitial) iron with relatively large localized magnetic moment strongly influences ordering temperature, shape and amplitude of the regular iron SDW order.

Despite existence of the single crystallographic site for the excess iron one sees at least three different kinds of these atoms. Such situation could occur due to the partial filling of the available interstitial sites by iron and due to some ordering (or clustering). The site with the highest magnetic hyperfine field is likely to contain almost isolated ions, i.e., surrounded by the vacancies on the interstitial sites.

The magnetism of the excess iron and SDW are coupled one with another. Both kinds of magnetism disappear at the same transition temperature.

Interstitial iron has relatively large localized magnetic moment. These moments interact strongly with the electrons having ability to form Cooper pairs and prevent appearance of the superconductivity. One has to remove interstitial iron to have a chance to get superconducting material.

A. Błachowski, K. Ruebenbauer, P. Zajdel, E.E. Rodriguez, M.A. Green,Mössbauer study of the ‘11’ iron-based superconductors parent compound Fe1+xTe,J. Phys.: Condens. Matter 24, 386006 (2012)

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Clarification as to why alcoholic beverages have the ability to induce superconductivity in Fe1+dTe1-xSx

K. Deguchi et al., Supercond. Sci. Technol. 25, 084025 (2012)

Clarification as to why alcoholic beverages have the ability to induce superconductivity in Fe1+dTe1-xSx

K. Deguchi et al., Supercond. Sci. Technol. 25, 084025 (2012)

”We found that the mechanism of inducement of superconductivity in Fe1+dTe1-xSx is the deintercalation of excess Fe from the interlayer sites.”