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.

(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

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

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)

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

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

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

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

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

(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