MOMENT Materials for Optical, Magnetic, and Energy Technologies - - PowerPoint PPT Presentation

▶
moment
SMART_READER_LITE
LIVE PREVIEW

MOMENT Materials for Optical, Magnetic, and Energy Technologies - - PowerPoint PPT Presentation

Oct 02, 2023 105 likes •445 views

MOMENT Materials for Optical, Magnetic, and Energy Technologies Semiconducting and half metallic Heusler compounds for multifunctional applications Claudia Felser JST-DFG 2009 Heusler Compounds as Multifunctional Materials 1905

slide-1
SLIDE 1

Semiconducting and half metallic Heusler compounds for multifunctional applications

Claudia Felser

Materials for Optical, Magnetic, and Energy Technologies

MOMENT

slide-2
SLIDE 2

JST-DFG 2009

Heusler Compounds as Multifunctional Materials

  • Magnetic

material: Cu2 MnAl

  • Halfmetallic

ferromagnet: NiMnSb

  • Magneto-optical:

PtMnSb

  • Magneto-mechanic:

Ni2 MnGa

  • Superconductor:

Pd2 YSn

  • Semiconductors:

CoTiSb

  • Heavy fermion:

Fe2 VAl

  • Li-conductor:

LiMnSb

  • Magneto-electronic:

Co2 FeSi

  • Thermo-electric:

TiNiSn

  • Magneto-caloric:

CoMnSb:Nb

1905 1983 2001

slide-3
SLIDE 3

JST-DFG 2009

  • Concept
  • Semiconducting Half Heusler
  • Thermoelectric materials
  • Diluted Semiconductors
  • Half metallic Heusler compounds
  • High Curie temperatures
  • Ferrimagnets
  • High energy photoemission for Devices
  • Summary
slide-4
SLIDE 4

JST-DFG 2009

  • Concept
  • Semiconducting Half Heusler
  • Diluted Semiconductors
  • Thermoelectric materials
  • Half metallic Heusler compounds
  • High Curie temperatures
  • Ferrimagnets
  • High energy photoemission for Devices
  • Summary
slide-5
SLIDE 5

JST-DFG 2009

Rational Design

  • First TMR device (Inomata

et al.) 19% at RT

  • TMR-device

with MgO (Marukame et al. APL 90 (2007) 012508) 109% TMR at RT ⇒ 88 % spin polarisation at 4K

  • Point contact

80% MR (Coey et al.)

Patent (Felser, Block, DE 101 08 760, H01 L43/08 ) Block, Felser, et al. J. Solid State Chem. 176, 646 (2003)

Half metallicity High density

  • f states

at EF Large MR at room temperature Intermag 2002: Co2 Cr0.4 Fe0.6 Al CCFA

slide-6
SLIDE 6

JST-DFG 2009

Synthesis Semiconducting Heuslers – Stuffed ZnS

XYZ X2 YZ

Ti Si2 As Ga Co Sb

9 + 4 + 5 = 18 3 + 5 = 8

Cu Li2 Sb V Fe2 Al

2*8 + 5 + 3 = 24 2*1 + 11 + 5 = 18

additional t2

  • levels
slide-7
SLIDE 7

JST-DFG 2009

Slater-Pauling Rule

Kübler 1983 Galanakis et al., PRB 66, 012406 (2002)

Magic valence electron number X2 YZ 24

Valence electrons =^24 + sat. magnetization Co2 FeAl 2*9 + 8 + 3 = 29 Ms = 5μB

  • B. Balke et al., Sci. Technol. Adv. Mater. 9 (2008) 014102.

EF

slide-8
SLIDE 8

JST-DFG 2009

  • Concept
  • Semiconducting Half Heusler
  • Thermoelectric materials
  • Diluted Semiconductors
  • Halfmetallic

Heusler compounds

  • High Curie temperatures
  • Ferrimagnets
  • High energy photoemission for Devices
  • Summary
slide-9
SLIDE 9

JST-DFG 2009

Half Heusler: 18 valence-electrons

Thermoelectrica

  • R. Asahi et al. J. Phys.: Cond. Mat. 20 (2008) 64227
  • K. Miyamoto et al. Appl. Phys. Express 1 (2008) 081901
  • E. Toberer, Nature Mat. 7 (2008) 105

VK Zaitsev et al. PRB 74 (2006) 045207

Typ Material Price in $/kg (metals )

V-VI Bi 2Te3 140 IV-VI PbTe 99 Zn4Sb3 Zn4Sb3 4 p-MnS i1.73 24 n-Mg2Si0.4Sn 0.6 18 Si0.80Ge0.20 660 Silicides Si0.94Ge0.06 270 Skutterutides CoSb3 11 Half-Heusler TiNiSn 55 n/p-Clathrate Ba8Ga16Ge30 1000 without Ba Oxides p-NaCo2O4, 17 without Na, O Zintl Phasen p-Yb14MnSb11 92 Th3P

4

La3-XTe4 160

Information H. Böttcher

200 400 600 800 1000 0,0 0,2 0,4 0,6 0,8 1,0 1,2 1,4 1,6 1,8

Bi2(Te0.8Se0.2)3 CoSb3 (Zr0.5Hf0.5)0.5Ti0.5NiSn0.998Sb0.002 Si0.8Ge0.2 (Hf0.5Zr0.5)NiSn (OFZ) Mg2Si0.8Sn0.2

Figure of merit ZT

Temperature T K

slide-10
SLIDE 10

JST-DFG 2009

Survey on HiTT –Materials

Half Heusler for Thermoelectrics

Balke et al. PRB 77, 045209 (2008) Kandpal et al. J. Phys. D 39 (2006) 776

−6 −4 −2 2 4 6 energy (eV) 10 20 30 40 TiCoSb VCoSn NbCoSn 10 20 30 40 DOS (states eV

−1 cell −1)

VFeSb TiCoSb YNiSb (a) (b)

100 200 300 400 500 600 700 800

  • 600
  • 500
  • 400
  • 300
  • 200
  • 100

(Zr0.5Hf0.5)Ti0.5NiSn0.998Sb0.002 TiCo0.93+xSb TiCoSb0.95Bi0.05

Seebeck coefficient S(T) [μVK

  • 1]

Temperature T [K]

T ZT λ σ α 2 =

α: Seebeck coeffizient σ: Electrical conductivity λ: Thermo conductivity T: Temperatur (K)

slide-11
SLIDE 11

JST-DFG 2009

Thermoelectrica

Barth et al., in preparation (2009) Improvement of the thermal conductivity Melt Spinning Ball milling – Spark Plasma Multilayer Nanoparticles Rattlers such as Lithium-Ions

19 20 21 22 23 24 5000 10000 15000 20000 25000 30000 35000 measured data Lorentz fit FW HM: ~0.86
  • Int. (cps)
ω (°)

30 40 50 60 70 80 90 5000 10000 15000 20000 25000 30000 35000 40000

Substrate

  • Int. (cps)

2θ (°)

TiNiSn on Al2O 3

Substrate (220)

100 200 300 400 500 600 700 800 10 100 1000

(Zr0.5;Hf0.5)Ti0.5NiSn0.998Sb0.002 TiCo0.93+xSb TiCo0.4Ni0.6Sb0.4Sn0.6

Resistivity R(T) [μΩm] Temperature T [K] 100 200 300 400 500 600 700 800 2 4 6 8 10

(Zr0.5Hf0.5)0.5TiNiSn0.998Sb0.002 TiCoSb TiNi0.9Co0.1Sn0.9Sb0.1 TiCo0.93+xSb

Thermal conductivity κ(T) [Wm

  • 1K
  • 1]

Temperature T [K]

slide-12
SLIDE 12

JST-DFG 2009

100 nm 50 nm 10nm 10 nm

First Heusler Nanoparticles: Co2 FeGa

Basnit et al. J. Phys. D, (2009) accepted

slide-13
SLIDE 13

JST-DFG 2009

For Spin Injection

XMCD-Investigation

  • n Fe

Kroth et al. APL 89 202509 (2006 ) Balke et al. PRB 77, 045209 (2008)

slide-14
SLIDE 14

JST-DFG 2009

Design of Diluted Semiconductors

Ti Si As Ga Co Sb Mn Fe/Mn

slide-15
SLIDE 15

JST-DFG 2009

  • Concept
  • Semiconducting Half Heusler
  • Diluted Semiconductors
  • Thermoelectric materials
  • Half metallic Heusler compounds
  • High Curie temperatures
  • Ferrimagnets
  • High energy photoemission for Devices
  • Summary
slide-16
SLIDE 16

JST-DFG 2009

Large temperature dependence of TMR ratio should be solved.

Tunneljunction

Sakuraba et al. APL 89 (2006) 052508 Sakuraba et al. APL 88 (2006) 192508

TMR ratio = 67%@RT, 580%@2K

Co2 MnSi Co2 MnSi Al2 O3

50 100 150 200 250 300 100 200 300 400 500 600

TMR [%] Temperature [K]

slide-17
SLIDE 17

JST-DFG 2009

Hal f m et al l i c f er r om agnet s

  • f or Tunnel m

agnet or esi st ance TM R

  • f or CPP G

M R W hat do we need? Hi gh Cur i e Tem per at ur e O r der ed L21 st r uct ur e G

  • od i nt er f aces

Adj ust ed EF : m i ddl e of t he gap no m agnons Desi gned el ect r oni c st r uct ur e

slide-18
SLIDE 18

JST-DFG 2009

High Curie Temperatures

Fecher, J. Appl. Phys. 99 (2006) 08J106 Kübler et al., Phys. Rev. B 76 (2007) 024414

Expected Curie temperature for Co2 FeSi : > 1000K

slide-19
SLIDE 19

JST-DFG 2009

Co2 FeSi

Magnetic moment in saturation: 5.97μB ±0.1μB at 5K Extrapolation to 0K :Slater-Pauling rule: 6 μB Curie Temperature 1120 K

  • 3
  • 2
  • 1

1 2 3

  • 6
  • 4
  • 2

2 4 6

  • 2.0k

0.0 2.0k

  • 1.0%
  • 0.5%

0.0% 0.5% 1.0%

5K 300K 775K Magnetic Moment per unit cell m [μB] Magnetic Field H [10

6 A/m]

Wurmehl, et al ., APL 88 (2006) 032502

.

Wurmehl, et al ., Phys. Rev. B 72 (2005) 184434

700 800 900 1000 1100 1200 1300 10 20 30 40 50 60

TC

1/χ(T)

Θ = 1150 ± 50 K σ(T)

TC = 1100 ± 20 K

μ0H = 0.1T

m = 47 μg Specific Magnetization σ [Am

2kg

  • 1]

Temperature T [K]

200 400 600 800

Inverse Susceptibility 1/χ 120 140 160 180 6 8 10 12 14 16 18 20 22 24 26 28

Hyperfeinfeld (T)

59Co Spin-Echo Intensity (arb. units)

Frequency (MHz)

slide-20
SLIDE 20

JST-DFG 2009

Heusler in Spintronic Devices: TMR

200 150 100 50 TMR (%)

  • 1000
  • 500

500 1000 Field (Oe) 500 400 300 200 Resistance (Ω)

TMR: 223%, 300K, A470°C, Rs: 1.74e+02Ω, RA: 1.74e+04 Ω⋅µm

2

10 x 10 µm

2

MU28225A470L300-5m223

300 K 223%

400 300 200 100 TMR (%) 1000 500

  • 500
  • 1000

Field (Oe) 1000 800 600 400 200 Resistance (Ω)

TMR: 423.40%, 7K, A470°C, Rs: 1.91e+02Ω, RA: 1.91e+04 Ω⋅µm

2

10 x 10 µm

2

MU28-2-25A470L007-2m423

7 K 423%

CFAS(30) IrMn MgO(2) CFAS (5) CoFe(1)

10 5 5 10 10 5 5 10 10 5 5 10 10 5 5 10

  • 10
  • 5

10 5 5 10

(a) Minority Majority (b) (c) Spin resolved density of states ρ(E) [eV

  • 1]

(d) (e) Energy E − εF [eV]

Fecher, Felser J. Phys. D 40 1582 (2007)

Co2 FeSi1-x Alx

  • N. Tezuka et al.,Jpn. J. Appl. Phys. 46, L454 (2007)
slide-21
SLIDE 21

JST-DFG 2009

Heusler in Spintronic Devices: CPP-GMR

Inomata et al. to be published

CoFeB/MgO‐MTJ Half‐metal + MgO MTJ CPP‐GMR with half‐metal CoFeB/MgO‐MTJ

Challenge: fitting spacer

Courtesy

  • f Koki

Takanashi, Sendai Interlayer exchange coupling!

slide-22
SLIDE 22

JST-DFG 2009

Fer r i m agnet s Appl i cat i on: Spi nt or que Com pensat ed f er r i m agnet ? no net m agnet i zat i on t wo m agnet i c subl at t i ces wi t h com pensat i ng m

  • m

ent s

W ar r en E. Pi cket t Phys. Rev. B 57 ( 1998) 10613.

slide-23
SLIDE 23

JST-DFG 2009

m2 m1 J ≈ 1 – 100 MA/cm2 J ≈ ― αMs HU d ħg e reduction

  • f α

& MS

Spin transfer switching

Courtesy after Shigemi Mizukami

Sloczewski 1996

slide-24
SLIDE 24

JST-DFG 2009

Halfmetallic Ferrimagnet

Kübler’s Rule Slater Pauling Rule Mn2 MnGa Two magnetic sublattice

  • 24 Valence electrons –

0 μB

  • Mn3+

at octahedral site – 4 μB

  • Mn

compensates ⇒Compensated ferrimagnet

Wurmehl, et al. J. Phys. Cond. Mat. 18 (2006) 6171 Balke et al. APL 90 (2007) 152504

slide-25
SLIDE 25

JST-DFG 2009

Compensated Ferrimagnet: Heusler

Mn2 MnGa

Low Moment – High Curie Temperature: low current for spinswitch Tetragonal distorted Heusler: Mn3+ Jahn Teller Ion

Balke et al. APL 90 (2007) 152504 Winterlik et al. Phys. Rev. B 77 (2008) 054406

Compensated ferrimagnet: 1μB Theoretical Spinpolarisation: 88% Curie temperature: 730 K

slide-26
SLIDE 26

JST-DFG 2009

Heusler and relates Structures

X2 MnZ XMnMnZ XCrCrZ

slide-27
SLIDE 27

JST-DFG 2009

  • Concept
  • Semiconducting Half Heusler
  • Diluted Semiconductors
  • Thermoelectric materials
  • Halfmetallic

Heusler compounds

  • High Curie temperatures
  • Ferrimagnets
  • High energy photoemission for Devices
  • Summary
slide-28
SLIDE 28

JST-DFG 2009

High Energy Photoemission

slide-29
SLIDE 29

JST-DFG 2009

High Energy Photoemission: buried films

Fecher et al. APL 92 195313 (2008) MgO substrate 50 nm Co2 MnSi 1nm AlOx MgO 2nm, 20nm

Films Yamamoto Sapporo Measurements SPring8 hν = 7.94 keV

slide-30
SLIDE 30

JST-DFG 2009

Film quality studied by High Energy PES

1nm AlOx

hν = 7.94 keV

  • 14
  • 12
  • 10
  • 8
  • 6
  • 4
  • 2

0.0 0.2 0.4 0.6 0.8 1.0 1.2

as-grown annealed Bulk Mn t2g ↑ Co t2g ↓ Mn eg ↑ Si a1g ↑↓ Relative intensity Energy E − εF (eV)

MgO substrate 30 nm Co2 MnSi 1nm AlOx MgO 2nm

Annealing and Irradiation improves the film quality

Ouardi et al. J. Phys. D (2009) accepted

slide-31
SLIDE 31

JST-DFG 2009

Summary

  • Half Heusler compounds (Stuffed ZnS) are candidates for

thermoelectric applications and for diluted semiconductors

  • Nanostructured Heuslers are need for low thermoconductivity
  • Heusler compounds are half metals with high Curie temperatures

Co2YZ

  • Compensated ferrimagnetic Heuslers Mn2YZ with 24

Valenceelectrons

  • Halfmetallic ferrimagnets for spintorque applicationMn2CoZ
  • High energy photoemission is an excellent tool to study devices
  • SPINHAXPES is needed
slide-32
SLIDE 32

JST-DFG 2009

Co-workers

JST-DFG Project:

  • NIMS, Tohoku:
  • K. Inomata
  • Saporro: M. Yamamoto
  • SPring8: K. Kobayashi

Dresden: S. Wurmehl Augsburg: A. Reller FG 559: G. Jakob, B. Hillebrands, J. Kübler, Y. Ando (Tohoku) DFG-FG559, FE633, SP1166, BMBF: HEUSPIN, MULTIMAG