experimental methods for the determination of magnetic, electrical and thermal transport properties...

Experimental methods for the determination of magnetic, electrical and thermal transport properties of

condensed matterJanez DolinšekJanez Dolinšek

FMF Uni-Ljubljana & J. Stefan Institute, LjubljanaFMF Uni-Ljubljana & J. Stefan Institute, Ljubljana

Magnetic, electrical and thermal transport properties

- Magnetic susceptibility- Electrical resistivity- Thermoelectric power- Hall coefficient- Thermal conductivity

Introduction

• Why to measure magnetic, electrical and thermal transport properties of solid materials ?

• Ever-present demand for new materials with novel/improved physical-chemical-mechanical properties• Novel materials preparation techniques were developed• High-quality single crystals available

• Complex metallic alloys (CMAs) and quasicrystals (QCs) offer unique physical properties or combinations of properties

Electrical conductor + thermal insulatorCombination of hardness + elasticity+ small friction coefficient

• Potential applications in high technology

Complex Metallic Alloys

• Intermetallic compounds• Giant unit cells• Cluster arrangement of atoms• Inherent disorder:

• Configurational• Chemical or substitutional• Partial or split occupation

quasicrystals ∞YbCu4.5 7448 at. / u. c.Ψ-Al-Pd-Mn 1480 at. / u. c.β-Al3Mg2 1168 at. / u. c.λ-Al4Mn 586 at. / u. c.Al39Fe2Pd21 248 at. / u. c.Mg32(Al,Zn)49 162 at. / u. c.Re14Al57 71 at. / u. c.elem. metals <5 at. / u. c.

Mg32(Al,Zn)49

Quasicrystals

• Discovered in1984

• Thermodynamically stable samples have appeared after 1990

• Well-ordered but nonperiodic solids

• Diffraction patterns with non-crystallographic point symmetry

Penrose tiling (quasiperiodic)Periodic tiling Diffraction pattern of a decagonal quasicrystal

Sample preparation

Czochralski methodBridgman method Flux-grown method

Single-crystal is cut in bar-shaped samples

•The first solidification zone

•Coexistence of solid and liquid phases

Czochralski method

Al-Co-Ni decagonal QC

Experimental methods

Magnetization and magnetic susceptibility measurement

H

M … magnetic susceptibility

SQUID magnetometer 5 T

Experimental methods

Measurement of the electrical conductivity

Electrical resistance:

R = U/I

l

SR

Specific resistivity:

PPMS – Physical Property Measurement System 9 T

Experimental methods

Thermoelectric effect

Experimental methods

Measurement of the thermoelectric power

Thermal conductivity measurement

TS

P qj

TSU

Experimental methods

Measurement of the Hall coefficient

BI

dU

Bj

E

BR

H

x

yHH

Hall coefficient

neH1

R

Magnetization vs. magnetic fieldY-Al-Ni-Co o-Al13Co4

Al4(Cr,Fe)

i-Al64Cu23Fe13

kHTHLMM ),,(0

kHJgBMJgBMM ),(),( 222111

FM contribution linear term

Curie magnetizations

ferromagnetic component

linear term

Magnetic susceptibilityY-Al-Ni-Co

o-Al13Co4Al4(Cr,Fe)

i-Al64Cu23Fe13

44

220)( TATA

T

CT

j

j0j T

C

Curie-Weisssusceptibility

temperature-independent term

temperature-dependent correction

Curie-Weisssusceptibility

temperature-independent term

Electrical resistivityY-Al-Ni-Co o-Al13Co4

PTC of the resistivity – predominant role of electron-phonon scattering mechanism (Boltzmann type)

Electrical resistivityAl4(Cr,Fe) i-Al64Cu23Fe13

is nonmetallic with NTC

slow charge carriers

j

j2j2

j2j

2

NBjBjj

Lgevge

)(

)()( FF

wpLvτ

pseudogap in ()

22

22

2

21

21

1 11)(

A

specific distribution of Fe

Thermoelectric power Y-Al-Ni-Co o-Al13Co4

Al4(Cr,Fe) i-Al64Cu23Fe13

Hall coefficient

Y-Al-Ni-Co o-Al13Co4Al4(Cr,Fe)

• RH values of QCs and CMAs are typical metallic

• RH’s exhibits pronounced anisotropy

• Fermi surface is strongly anisotropic

• consists of hole-like and electron-like parts

Thermal conductivity

Y-Al-Ni-Co o-Al13Co4 Al4(Cr,Fe)

• Total is a sum of the electronic el and the phononic ph contribution

• el is estimated from the Wiedemann-Franz law: el=2kB2T(T)/3e2

• WF law valid when elastic scattering of electrons is dominant

Thermal conductivity

i-Al64Cu23Fe13

)()()()( HDel TTTT

long wave phonons

(Debye model)

electronic part hopping of localized vibrations

• 300K < 1.7 W/mK lower than SiO2 (2.8 W/mK)

Thank you for your attention !