Transcript Slide 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 Cambridge CNRS, Wuezburg, Warsaw, Thales Texas Universities Jairo Sinova, Allan H. MacDonald. et al. Jorg Wunderlich, David Williams, Andrew Irvine, Kaiyou Wang, Elisa De Ranieri, et al. (Ga,Mn)As (and realated DMSs) & spintronics: Ideal systems for exploring basic physics and new functionality concepts s Ga As Mn p py V Hso Mn px Dilute moment ferromagnets based on semiconductor material: Ferromagnetic Mn-Mn coupling mediated by GaAs host-like As p-orbital band states: dependence on doping strongly exchange split and SO coupled yet relatively simple carrier bands low saturation magnetization 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 majority _ __ FSO FSO I 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 M Origin of AMR Basic symmetry arguments for zincblende DMSs (GaMnAs) SO-coupling – spherical model FM exchange spiitting ky ~(k . s)2 scattering rate kx M ~Mx . sx current [110] hot spots for scattering of states moving M R(M I)> R(M || I) Successful microscopic modelling still R(M I)> R(M || I) plus magnetocrystalline anisotropy corrections (M vs. crystal axes) AMRtheor. AMRexp. A family of new AMR effects dicovered in GaMnAs - TAMR sensor/memory elemets TAMR TMR no need for exchange biasing or spin Au coherent tunneling 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 Spintronic transistor based on CBAMR Source Q VD Drain Gate VG ( Q Q0 ) ( M ) C U & Q0 CG [ VG VM ( M )] &VM 2C e CG 2 electric & magnetic control of Coulomb blockade oscillations magnitude of MR reaches magnitude of CB oscillations M || <111> Strong spin-orbit coupling band structure depends on M M || <100> chemical potential depends on M • CBAMR if change of |(M)| ~ e2/2C • In (Ga,Mn)As ~ meV (~ 10 Kelvin) • In room-T ferromagnet change of |(M)|~100K 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 s Ga As Mn p py V Hso Mn px Dilute moment ferromagnets based on semiconductor material: Ferromagnetic Mn-Mn coupling mediated by GaAs host-like As p-orbital band states: dependence on doping strongly exchange split and SO coupled yet relatively simple carrier bands low saturation magnetization unprecedented micromagnetics Jorg Wunderlich's talk