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