Dilute moment ferromagnetic semicinductors for spintronics
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Transcript of Dilute moment ferromagnetic semicinductors for spintronics
Dilute moment ferromagnetic semicinductors for spintronicsDilute moment ferromagnetic semicinductors for spintronics
Tomas Jungwirth
Jan Mašek, Alexander Shick Karel Výborný, Jan Zemen,
Vít Novák, et al.
Bryan Gallagher, Tom Foxon, Richard Campion,
Kevin Edmonds, Andrew Rushforth, Devin
Giddings, Chris King, et al.
Jorg Wunderlich, David Williams, Andrew Irvine, Kaiyou Wang, Elisa De
Ranieri, et al. Cambridge
Nottingham Prague
NANOSPIN
CNRS, Wuezburg,
Warsaw, ThalesTexas Universities
Jairo Sinova, Allan H.
MacDonald. et al.
(Ga,Mn)As (and realated DMSs) & spintronics:Ideal systems for exploring basic physics and new functionality concepts
Mn
Ga
As Mn
Ferromagnetic Mn-Mn coupling mediated byGaAs host-like As p-orbital band states:
strongly exchange split and SO coupled yet relatively simple carrier bands
px
py
Dilute moment ferromagnets based on semiconductor material:
dependence on doping
low saturation magnetization
V
HHsoso
pss
Spintronics based on extraordinary magnetoresistance effects (AHE, AMR, STT,TMR,....)
Extraordinary magnetoresistance:response to internal magnetization in ferromagnets often via quantum-relativistic spin-orbit coupling
I
_ FSO
FSO
_ __majority
minority
Ve.g. anomalous Hall effect
anisotropic magnetoresistance
For decades controversial in conventional metal FMs: model of (non-SO-coupled non-exchange-split) s-state carriers and localized d-states difficult to match with microscopic bands of mixed s-d character
Origin of AMR
~(k . s)2 ~Mx . sx
SO-coupling – spherical model FM exchange spiitting
hot spots for scattering of states moving M R(M I)> R(M || I)
ky
kx
M
scattering rate
M
[110]
current
))
Basic symmetry arguments for zincblende DMSs (GaMnAs)
Successful microscopic modelling
still R(M I)> R(M || I) plus
magnetocrystalline anisotropy corrections
(M vs. crystal axes)
AMRtheor. AMRexp.
TAMR
Au
TMR
- CBAMR spintronic transistor
combining processing withpermanent storage and p-typeand n-type transistor characteristics
- TAMR sensor/memory elemets
no need for exchange biasing or spin coherent tunneling
A family of new AMR effects dicovered in GaMnAs
predicted and recently confirmed to exist in conventional metal FMs
predicted to exists in conventional metal FMs
Single-electron transistor
Two "gates": electric and magnetic
Spintronic transistor based on CBAMR
Huge, gatable, and hysteretic MR
Spintronic transistor based on CBAMR
Source Drain
GateVG
VDQ
GMMGG0
20
C
C
e
)M(V&)]M(VV[CQ&
C2
)QQ(U
electric && magneticmagnetic
control of Coulomb blockade oscillations
magnitude of MR reaches magnitude of CB oscillations
• CBAMR if change of |CBAMR if change of |((MM)| ~ )| ~ ee22//22CC
• In (Ga,Mn)As ~ meV (~ 10 Kelvin)In (Ga,Mn)As ~ meV (~ 10 Kelvin)
• In room-T ferromagnet change In room-T ferromagnet change of |of |((MM)|~100K )|~100K
Strong spin-orbit coupling band structure depends on M
chemical potential depends on M
M || <111>
M || <100>
• Generic effect in FMs with SO-coupling
• ~10 K in GaMnAs, ~100 K in room-Tc metal FM
• Combines electrical transistor action with magnetic storage
• Switching between p-type and n-type transistor by M programmable logic
CBAMR SET
(Ga,Mn)As (and realated DMSs) & spintronics:Ideal systems for exploring basic physics and new functionality concepts
Mn
Ga
As Mn
Ferromagnetic Mn-Mn coupling mediated byGaAs host-like As p-orbital band states:
strongly exchange split and SO coupled yet relatively simple carrier bands
px
py
Dilute moment ferromagnets based on semiconductor material:
dependence on doping
low saturation magnetization
V
HHsoso
pss
unprecedented micromagnetics Jorg Wunderlich's talk