MAP – FIS 2011/2012
Universidade do Minho, MAP-FIS Conf.
Overview
Advanced materials science
MAP-FIS conference
Session
MAP – FIS 2011/2012
Universidade do Minho, MAP-FIS Conf.
- Multiferroic materials
- Magnetocaloric
- Nanowires/nanotubes (magnetic, for photoelectrochemical
water splitting)
- Quantum dots
Preparation techniques:
- Templated growth
- Electodeposition
- Others
Applications
Presentations
MAP – FIS 2011/2012
Universidade do Minho, MAP-FIS Conf.
Nanowires/Nanofibres/
Nanotubes
Wide range of application:
- Sensors, nanodevices, magnetic storage
- Tissue engineering
- Biodevices and systems, nanomedicine
- Fundamental studies of cell biology (role of cell nanostructures in guiding cell behavior)
- Optics (e.g., metamaterials)
MAP – FIS 2011/2012
Universidade do Minho, MAP-FIS Conf.
Top-down
-Top-down
- Litography
-e.g., focused ion-beam miling (FIB)
- e.g., electron-beam direct writing
FIB EBDW
MAP – FIS 2011/2012
Universidade do Minho, MAP-FIS Conf.
Self-assembled porous
templates
J. Vac. Sci. Technol. B
Porous Al2O3 templatePorous templates:- self-organized pores- Block copolymers- Anodic Aluminum oxide (Al2O3)
Porous alumina (anodic aluminum oxide) templates:- controllable pore diameter- narrow pore size distribution- self-ordered honeycomb lattice of nanopores after a two-step anodization process- Pore diameters of 11 nm and periods of 40 nm (or more) have been achieved
Electrodeposition- DC or pulsed (smaller particles)- Able to coat non-flat surfaces
Polycyclohexylethylene (PCHE)diblock co-polymer template
Chem. Mater.
MAP – FIS 2011/2012
Universidade do Minho, MAP-FIS Conf.
Electrophoretic Deposition
p-Si
(001
)
Si/SiO2 /TiO
2 /Pt
25V
20mm- Suspension of charged particles
- Electric field applied to electrodes
- Particles are deposited on the substates
- Controled particle sizes. They can be very
small (~30 nm or less)
- Functional thin films
-Can be applied with different materials and combinations of materials
- Able to form films on a wide range of shapes and 3D complex and porous structures
- It is able to be scaled-up to large volumes and sizes
MAP – FIS 2011/2012
Universidade do Minho, MAP-FIS Conf.
Nanocontac
ts
- Pt nanocontacts for nanocapacitors- Electrochemically deposited
BaTiO3
Science
Pt nanowires
Lowerelectrode
0.2 m
MAP – FIS 2011/2012
Universidade do Minho, MAP-FIS Conf.
PZT nanocapacitors
M. Alexe, et al, Advanced Materials
film-type(with top nanocontacts)
island-type
Nanocapacitors
Nano-capacitors for
integrated electronics
MAP – FIS 2011/2012
Universidade do Minho, MAP-FIS Conf.
Biomimetic cilia
-Sensing sound (acoustic)
- Fluid flow
Silicon-nitride suspending membranes with polymer cilia on topElectrodes on membrane and substrate form a variable capacitor for readout
Nanowires -
Biomimetic
Journal of Bionic Engineering
MAP – FIS 2011/2012
Universidade do Minho, MAP-FIS Conf.
Magnetic nanowires
- Patterned arrays
- Information storage (high density)
- Biological applications (e.g., magnetic carrier to
manipulate functionalized particles in suspensions)
- Magneto-optical
- High-aspect ratio wires through anodic aluminum
oxide templates (up to 50 m long)
- Magnetic anisotropy studies
Nanowires - Magnetic
Array of Fe nanowires
200nm diam, 10m long
Nanotechnology
Ni nanowires
λlaser=632.8 nm
MAP – FIS 2011/2012
Universidade do Minho, MAP-FIS Conf.
Magnetocaloric Materials
- Magnetocaloric effect
- Changing magnetic fields induces changes in the materials temperature
- Magnetic refrigeration
MAP – FIS 2011/2012
Universidade do Minho, MAP-FIS Conf.
Magnetocaloric Materials
lattice
L
electronic
E
magnetic
M TSTSTHSTHS )()(),(),( Entropy:
Magnetocaloric effect
- Application of a magnetic field H -> magnetic material is heated
- Reversible process (cooled upon H removal)
- Change in magnetic entropy
Effect is higher near Tc
Adiabatic Isothermal
MAP – FIS 2011/2012
Universidade do Minho, MAP-FIS Conf.
Magnetocaloric MaterialsGiant magnetocaloric effect
- Strong changes in entropy near Tc
- First order magnetic phase transition
- e.g., Gd5Si2Ge2
5TeslaGd5Si2Ge2
V.K. Pecharsky, Phys. Rev. Lett. (1997)
Gd5Si2Ge2 : PM->F(I) at T~300K (2nd order); F(I)->F(II) at T ~ 277 K (1st order); Magneto-structural (~282-289K)
HT
mag
T
M
H
S
2
1
1H
H Had dH
T
MT
CT
T
dTT
THCTHS
0
),(),(
M (e
mu/
g
MAP – FIS 2011/2012
Universidade do Minho, MAP-FIS Conf.
Magnetocaloric MaterialsApplications - Magnetic refrigeration
-e.g., cooling integrated circuits
- avoids fans and complex dissipators
- compact and fully solid-state
-New materials to:
- widen the applicable temperatures
- use of lower magnetic fields
MAP – FIS 2011/2012
Universidade do Minho, MAP-FIS Conf.
Magnetocaloric MaterialsOther effects for cooling
- Magnetic field dependant thermal conductivity
- Application of magnetic field increases K1 and decreases
K2 (changing heat transfer)
- Avoids refrigeration fluids completely
- e.g., LaCaMnO3 (K = 0.125 W/mK (0T), 0.085 W/mK (8T)
Science
PZT
Giant electrocaloric effectIn ferroelectric materials
2
1
1E
E Ead dE
T
PT
CT
ET T
P
E
S
K1 < K2 K1 + K1 > K2 - K2
K1 ->
K2 ->
MAP – FIS 2011/2012
Universidade do Minho, MAP-FIS Conf.
Multiferroic MaterialsMultiferroic materiais combine, at least, two ferroic orders:-Ferroelectricity-Ferromagnetism -Ferroelasticity Some insulator oxides
Magnetoelectric materials exhibit a coupling between their electric and magnetic degrees of freedom
MAP – FIS 2011/2012
Universidade do Minho, MAP-FIS Conf.
Multiferroic Materials
The magnetoelectric response (ME), in multiferroic (MF) systems:-appearance of an electric polarization (P) upon applying a magnetic field (H)- and/or appearance of a magnetization (M) upon applying an electric field (E)
- Single phase- Composites -> coupling through strain
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2
12
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1),( 000Free energy
jiijkkjijk
me
jijjijSi
ii EHHHHEP
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FP
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10
Polarization
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FM
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Magnetization ij – induction of a polarization (magnetization) due to a magnetic (electric) field. Linear ME effect
MAP – FIS 2011/2012
Universidade do Minho, MAP-FIS Conf.
Multiferroic MaterialsPotencial applications:-magnetic field sensors, current measurement probes, transducer, filters, oscillators, phase shifters, memory devices- Higher ME on laminated composites
Sensitive to low H freq. ac fields
Tunable microwave line
MAP – FIS 2011/2012
Universidade do Minho, MAP-FIS Conf.
Multiferroic MaterialsSingle-phase multiferroics
emme
- limitation of single-phase materials -> search new materials, Or -> strain coupling ME -> composites
- ferroelectricity and magnetism have independent sources with some coupling between them- ferroelectricity typically appears at higher temperatures than magnetism- perovskyte type ferroelectrics, charge-ordering, tilting of unit cell blocks- spontaneous polarization P is often large (10 – 100 C/cm2)- e.g., BiFeO3 (TFE~1100K, TN= 643 K, P ~ 90 C/cm2); YMnO3 (TFE~914K, TN= 76 K, P ~ 6 C/cm2 )
Type I
Type II
Off-centering
Charge-ordering
tilt
Lone pair
Spiral magnetic phase
- magnetism causes ferroelectricity, implying a strong couplingbetween them- polarization in these materials is usually much smaller ( ~ 10-2 C/cm2)- e.g., TbMnO3, Ni3V2O6, or MnWO4
MAP – FIS 2011/2012
Universidade do Minho, MAP-FIS Conf.
Piezoelectric Phase + Magnetostrictive Phase
Magnetoelectric (ME) response
Elastic interactions
Multiferroic composites
2-2 multilayer0-3 granular 1-3 vertical
- Laminated composites – high ME response- Thin films
H
EE
- When a magnetic field is applied to the composite, the magnetic phase changes its shape magnetostrictively. Strain is then passed along to the piezoelectric phase, resulting in an electric polarization. For the converse effect a similar coupling is obtained.
MAP – FIS 2011/2012
Universidade do Minho, MAP-FIS Conf.
Piezoelectric Phase + Magnetostrictive Phase
Magnetoelectric (ME) response
Elastic interactions
Multiferroic composites
Advantages - High magnetization and electric polarization- Higher ME response as compared with single phase
H
EE
MAP – FIS 2011/2012
Universidade do Minho, MAP-FIS Conf.
Multiferroic nanostructuresMotivation:- on nanostructures high electric fields can be applied with small voltages- energy consumption
Magnetoresistance
Electroresistance(bias E-field)
Materials Science and Engineering R
MAP – FIS 2011/2012
Universidade do Minho, MAP-FIS Conf.
-Feixe laser, pulsado, incide no alvo.
-Radiação laser é absorvida pela superfície sólida do alvo e a energia electromagnética é convertida em energia térmica, causando assim a evaporação explosiva, ou seja a “pluma”.
-No interior da pluma, o livre percurso médio é pequeno e, como tal, logo depois da irradiação do laser no alvo a pluma rapidamente se expande sob a forma de um jacto que é perpendicular ao alvo.
- As partículas são recolhidas num substrato de modo a formar um filme. Depende da distância alvo-substrato, e da posição da pluma em relação ao substrato.
Pulsed laser ablation
(PLD)
MAP – FIS 2011/2012
Universidade do Minho, MAP-FIS Conf.
Self-assembled magnetoelectric nanostructures- Imiscible materials- Matrix: Piezoelectric. P, E.- Colums: Magnetostrictive. M, H.- Stress mediated coupling => P versus H.
M versus E- Laser ablation
Zheng et al., Science , (2004)
Multiferroic Nanostructures
-Others: BaTiO3/NiFe2O4, PZT/BaTiO3/CoFe2O4, etc
BaTiO3/CoFe2O4
MAP – FIS 2011/2012
Universidade do Minho, MAP-FIS Conf.
Multiferroic NanostructuresMagnetic thin film on a piezoelectric substrate- R(1-x)A(x)MnO3 Manganite films- Strain: changes Mn-O bond-lenghts and Mn-O-Mn angles- Mismatch with substrate affects: structural (unit cell distortion), electrical (metallic phase) and magnetic properties (anisotropy, Tc changes)- CMR tuning and CO-melting- e.g., LaCaMnO3/PMN-PT, LaSrMnO3/LiNbO3
20 30 40 50 60 70 80 900
10
20
30
40
50
60
(0012)LiNbO3
Inte
nsit
y (1
03 cps)
2 (deg)
(006)LiNbO
3
(111)LSMO
(222)LSMO
a)
Phil. Mag.
MAP – FIS 2011/2012
Universidade do Minho, MAP-FIS Conf.
Granular magnetoelectric thin films and composites
Matrix Grains - Magnetostrictive grains in a piezo matrix
-Matrix: Piezoelectric. P, E.
- Grains: Magnetostrictive. M, H.
- 0-3 composite
Multiferroic Nanostructures
115010~
OecmmVH
EE
- e.g., BaTiO3/CoFe2O4, PZT/NiFe2O4
C.W. Nan, (1994)
BaTiO3/CoFe2O4
fCFO = 0.8
MAP – FIS 2011/2012
Universidade do Minho, MAP-FIS Conf.
PZT-CoFe2O4 nanocomposites
ACS NanoNanodots Nanograins inside a Matrix
Multiferroic
nanostructures
MAP – FIS 2011/2012
Universidade do Minho, MAP-FIS Conf.
Conclusions
- New materials
- Combination of different physical properties and techniques
- Modeling physical behavior
- New designs for applications
MAP – FIS 2011/2012
Universidade do Minho, MAP-FIS Conf.
15:45 Probing Electrostructural Coupling on Magnetoelectric CdCr2S4
Speaker: Gonçalo Oliveira
16:00 Effect of la substitution on Tb5Si2Ge2 compound: structural and magnetic properties Speaker: João Horta Belo
16:15 - 17:00 Coffee Break + Poster Session
17:00 Ordered arrays of electrodeposited nanowires and nanotubes: comparing magnetic propertiesSpeaker: Mariana Proença
17:15 Hematite nanowires for solar water splitting: development and structure optimizationSpeaker: João Azevedo
17:30 Critical behaviour of a three-dimensional hardcore cylinders composite systemSpeaker: Jaime Silva
17:45 Dynamic electronic interactions at nanoscopic scaleSpeaker: Marcelo Barbosa
18:00 Exchange coupled donor dimers in nanocrystal quantum dotsSpeaker: António José Almeida
Session