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.

Overview

Advanced materials science

MAP-FIS conference

Session

MAP – FIS 2011/2012


- Multiferroic materials

- Magnetocaloric

- Nanowires/nanotubes (magnetic, for photoelectrochemical

water splitting)

- Quantum dots

Preparation techniques:

- Templated growth

- Electodeposition

- Others

Applications

Presentations

MAP – FIS 2011/2012


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


Top-down

-Top-down

- Litography

-e.g., focused ion-beam miling (FIB)

- e.g., electron-beam direct writing

FIB EBDW

MAP – FIS 2011/2012


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


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


Nanocontac

ts

- Pt nanocontacts for nanocapacitors- Electrochemically deposited

BaTiO3

Science

Pt nanowires

Lowerelectrode

0.2 m

MAP – FIS 2011/2012


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


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


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


Magnetocaloric Materials

- Magnetocaloric effect

- Changing magnetic fields induces changes in the materials temperature

- Magnetic refrigeration

MAP – FIS 2011/2012


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


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


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


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


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


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

kjiijkkjiijk

jiijjiijjiijiSii

Si

EEHHHE

HEHHEEHMEPFHEF

2

1

2

12

1

2

1),( 000Free energy

jiijkkjijk

me

jijjijSi

ii EHHHHEP

E

FP

2

10

Polarization

kjijkjiijk

me

iijjijSi

ii EEHEEHM

H

FM

2

10

Magnetization ij – induction of a polarization (magnetization) due to a magnetic (electric) field. Linear ME effect

MAP – FIS 2011/2012


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


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


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


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


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


-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


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


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


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


PZT-CoFe2O4 nanocomposites

ACS NanoNanodots Nanograins inside a Matrix

Multiferroic

nanostructures

MAP – FIS 2011/2012


Conclusions

- New materials

- Combination of different physical properties and techniques

- Modeling physical behavior

- New designs for applications

MAP – FIS 2011/2012


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

Documents

MAP – FIS 2011/2012 Universidade do Minho, MAP-FIS Conf. Overview Advanced materials science MAP-FIS conference Session