Spintronics: How Spin Impacts Charge Carriers
Learn about the fascinating world of spintronics and how spin can influence charge carriers, as explained by Tomas Jungwirth from the University of Nottingham Institute of Physics in Prague. Explore the potential of spintronics in various applications such as magnetic field control and writing by current via spin torques.
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Presentation Transcript
Spintronics: How spin can act on charge carriers and vice versa Tomas Jungwirth University of Nottingham Institute of Physics Prague
Mott without spin current Mott with spin current Spintronics I 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 I AMR 1857 HD Read-heads 1990 s
Mott with antiferromagnets Mott with ferromagnets I I I I Dirac with ferromagnets Dirac with antiferromagnets I 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 s Pn Pn M M s M M N mec, Tesa ov , Nov k, 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 s Pn Pn M M s N mec, Tesa ov , Nov k, 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 s Pn Pn M M s N mec, Tesa ov , Nov k, 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 M s 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 ex + + 2) 1 ( / s / ex s 2) 1 ( / ex s = / NASTT / STT AD 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 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 Zhang & Li, PRL 93, 127204 (2004) Vanhaverbeke & Viret, PRB 75, 024411 (2007) Field-like STT
Electrical spin-transfer torque: current induced DW motion vDW > < j jC jC Antidamping STT Antidamping-like STT Zhang & Li, PRL 93, 127204 (2004) Vanhaverbeke & Viret, PRB 75, 024411 (2007) Field-like STT
s d M Steady-state carrier spin polarization torque dt QM averaging in non-equilibrium Electrical spin injection Non-relativistic STT P n Steady state Optical spin injection External P n antidamping-like torque M
s d M Steady-state carrier spin polarization torque dt QM averaging in non-equilibrium Electrical spin injection Relativistic SOT Internal Steady state Optical spin injection M
s d M Steady-state carrier spin polarization torque dt Linear response: eigenstates of H & non-equilibrium distribution Electrical drift and relaxation: broken inversion symmetry Relativistic SOT s s Internal Steady state M Optical generation and relaxation s s
Paramagnets Spin-orbit Magnetic field of moving nucleus in electron s rest frame Spin-galvanic effect s M = SOT without acting on 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?
