Transcript Part 3
Spintronics: How spin can act on charge carriers and vice versa Tomas Jungwirth Institute of Physics Prague University of Nottingham Mott without spin current Mott with spin current I Spintronics I From Wikipedia, the free encyclopedia Spintronics (a pormanteau meaning spin transport electronics).... GMR 1988 MRAM 2006 Dirac without current through magnet Dirac with current through magnet I AMR 1857 I HD Read-heads 1990‘s Mott with antiferromagnets Mott with ferromagnets I I I Dirac with ferromagnets I I Dirac with antiferromagnets I I I Magnetic-field control of FMs: scales with current Control by current via spin torques: scales with current density Control by photo-carriers via spin torques: sub ps timescales 0.1 pJ Relativistic spin-orbit torques might work equally well in AFMs plus photocarriers in SCs Electro-static field control via relativistic magnetic anisotropy effects: 1fJ Should work equally well or better in AFMs: more choices including SCs (or piezo-electric) Writing by current via spin torques: scales with current density Writing by photo-carriers via spin torques: sub ps timescales 0.1 pJ Relativistic spin-orbit torques might work equally well in AFMs plus photocarriers in SCs Optical spin-transfer torque OSTT Pn s M M s Pn M M Němec, Tesařová, Novák, TJ et al. Nature Phys.’12, Nature Photonics ‘13, Nature Commun. ‘13 Fernandez-Rossier, Nunez, Abofath, MacDonald cont-mat/0304492 Optical spin-transfer torque OSTT Pn s s Pn M M Němec, Tesařová, Novák, TJ et al. Nature Phys.’12, Nature Photonics ‘13, Nature Commun. ‘13 Fernandez-Rossier, Nunez, Abofath, MacDonald cont-mat/0304492 Optical spin-transfer torque OSTT Pn s s Pn M M Němec, Tesařová, Novák, TJ et al. Nature Phys.’12, Nature Photonics ‘13, Nature Commun. ‘13 Fernandez-Rossier, Nunez, Abofath, MacDonald cont-mat/0304492 Electrical spin-transfer torque Antidamping-like (adiabatic) STT OSTT Pn s M Zhang and Li PRL 2004 Vanhaverbeke et al. PRB 2007,...... Electrical spin-transfer torque Field-like (non-adiabatic) STT s Pn M Zhang and Li PRL 2004 Vanhaverbeke et al. PRB 2007,...... Electrical spin-transfer torque Antidamping-like STT Field-like STT ~ 1 1 ( ex / s ) 2 ex / s 1 ( ex / s ) 2 STTNA / STTAD ex / s small in weakly SO-coupled dense-moment metal FMs large in strongly SO-coupled dilute-moment (Ga,Mn)As Electrical spin-transfer torque: current induced DW motion Electrical spin-transfer torque: current induced DW motion vDW =0 “intrinsic” pinning j jC Antidamping STT Antidamping-like STT Zhang & Li, PRL 93, 127204 (2004) Vanhaverbeke & Viret, PRB 75, 024411 (2007) Electrical spin-transfer torque: current induced DW motion vDW < j jC Antidamping STT Antidamping-like STT Field-like STT Zhang & Li, PRL 93, 127204 (2004) Vanhaverbeke & Viret, PRB 75, 024411 (2007) Electrical spin-transfer torque: current induced DW motion vDW > < j jC jC Antidamping STT Antidamping-like STT Field-like STT Zhang & Li, PRL 93, 127204 (2004) Vanhaverbeke & Viret, PRB 75, 024411 (2007) Steady-state carrier spin polarization s torque dM dt QM averaging in non-equilibrium Electrical spin injection Non-relativistic STT Pn Steady state Optical spin injection External antidamping-like torque Pn M Steady-state carrier spin polarization s torque dM dt QM averaging in non-equilibrium Electrical spin injection Relativistic SOT Internal Steady state Optical spin injection M s Steady-state carrier spin polarization torque dM dt Linear response: eigenstates of H & non-equilibrium distribution Electrical drift and relaxation: broken inversion symmetry Relativistic SOT s Internal Steady state s M Optical generation and relaxation s s Paramagnets Spin-orbit Magnetic field of moving nucleus in electron‘s rest frame Spin-galvanic effect = SOT without s acting on M Electrical drift and relaxation: broken inversion symmetry s Aronov, Lyanda-Geller, JETP ’89, Edelstein SSC ’90, Ganichev et al. Nature ‘02 Paramagnets Spin-orbit Magnetic field of moving nucleus in electron‘s rest frame Spin Hall effect MRAM switching by in-plane current SHE spin-current non-relativistic STT Ralph, Buhrman,et al., Science ‘12 Hall antidamping STT SHE in Pt acts as the external polarizer MRAM switching by in-plane current attractive alternative to perp. current STT Conventional perpendicular current STT MRAM switching by in-plane current attractive alternative to perp. current STT Conventional perpendicular current STT Competing scenario: In-plane current swithing by relativitic SOT due to broken structural inversion symmetry at Co/Pt? Miron et al., Nature ‘11 Ralph, Buhrman et al.: SHE Miron et al.: SOT -We see antidamping-like torque -We also see antidamping-like torque -SOT is field-like so we exclude it -SOT is field-like but maybe there is some antidamping-like SOT as well - non-relativistic STT in metals is dominated by the antidamping torque Where could a comparable strength antidamping-like SOT come from?