1. Dilute moment ferromagnetic semicinductors for spintronics
Tomas Jungwirth
Bryan Gallagher, Tom Foxon, Richard Campion,
Kevin Edmonds,
Andrew Rushforth, Devin Giddings, Chris King, et al.
Jan Mašek, Alexander Shick
Karel Výborný, Jan Zemen,
Vít Novák, et al.
Nottingham
Prague
NANOSPIN
Jorg Wunderlich, David Williams, Andrew Irvine, Kaiyou Wang, Elisa De Ranieri, et al.
Cambridge
CNRS, Wuezburg,
Warsaw, Thales
Texas Universities
Jairo Sinova, Allan H.
MacDonald. et al.

2. (Ga,Mn)As (and realated DMSs) & spintronics:
Ideal systems for exploring basic physics and new functionality concepts V
Hso p s px py Mn Ga As
Dilute moment ferromagnets based on semiconductor material:
dependence on doping
low saturation magnetization
Ferromagnetic Mn-Mn coupling mediated by
GaAs host-like As p-orbital band states:
strongly exchange split and SO coupled
yet relatively simple carrier bands

3. Spintronics based on extraordinary magnetoresistance effects (AHE, AMR, STT,TMR,....)
response to internal magnetization in ferromagnets
often via quantum-relativistic spin-orbit coupling I _
FSO
majority
minority V
e.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

4. Origin of AMR Basic symmetry arguments for zincblende DMSs (GaMnAs)
SO-coupling – spherical model
FM exchange spiitting ky kx
scattering rate M
[110]
current )  
~(k . s)2
~Mx . sx
hot spots for scattering of states moving  M
 R(M  I)> R(M || I)
Successful microscopic modelling
AMRtheor.
AMRexp.
still R(M  I)> R(M || I) plus
magnetocrystalline anisotropy corrections
(M vs. crystal axes)

5. A family of new AMR effects dicovered in GaMnAs
- TAMR sensor/memory elemets
TAMR
TMR
no need for exchange biasing
or spin coherent tunneling Au
predicted and recently confirmed to exist in conventional metal FMs
- CBAMR spintronic transistor
combining processing with
permanent storage and p-type
and n-type transistor characteristics
predicted to exists in conventional metal FMs

6. Spintronic transistor based on CBAMR
Huge, gatable, and hysteretic MR
Single-electron transistor
Two "gates": electric and magnetic

7. Source Drain Gate VG VD Q Spintronic transistor based on CBAMR
electric &
magnetic
control of Coulomb blockade oscillations 
magnitude of MR reaches magnitude of CB oscillations

8. Strong spin-orbit coupling  band structure depends on M
 chemical potential depends on M
M || <100>
CBAMR if change of |(M)| ~ e2/2C
In (Ga,Mn)As ~ meV (~ 10 Kelvin)
In room-T ferromagnet change
of |(M)|~100K

9. Generic effect in FMs with SO-coupling
CBAMR SET
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

10. (Ga,Mn)As (and realated DMSs) & spintronics:
Ideal systems for exploring basic physics and new functionality concepts V
Hso p s px py Mn Ga As
Dilute moment ferromagnets based on semiconductor material:
dependence on doping
low saturation magnetization
Ferromagnetic Mn-Mn coupling mediated by
GaAs host-like As p-orbital band states:
strongly exchange split and SO coupled
yet relatively simple carrier bands
unprecedented micromagnetics  Jorg Wunderlich's talk