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CECAM June 2003, Lyon (FR)

cond-mat/0304492. CECAM June 2003, Lyon (FR). Optical spin transfer in GaAs:Mn Joaquin Fernandez-Rossier, Department of Applied Physics, University of Alicante (SPAIN). and A. Núñez , M. Abolfath and A. H. MacDonald Department of Physics, University of Texas at Austin. Main Ideas.

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CECAM June 2003, Lyon (FR)

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  1. cond-mat/0304492 CECAM June 2003, Lyon (FR) Optical spin transfer in GaAs:MnJoaquin Fernandez-Rossier, Department of Applied Physics, University of Alicante (SPAIN) and A. Núñez , M. Abolfath and A. H. MacDonald Department of Physics, University of Texas at Austin

  2. Main Ideas • Optical control of magnetization dynamics • Optical injection of electrons and holes in GaAs:Mn • with spin perpendicular to magnetization • Spin transfer in GaAs:Mn

  3. Co Co Cu Magnetization dynamics under electrical spin injection Current Current Induced Magnetization Switching (CIMS) E.B. Myers et al.,Science 285, 867 (1999).

  4. GaAs GaAs Magnetization dynamics under c.w. optical spin injection (Ga,Mn)As Light Induced Magnetization tilt (LIMT) Oiwa et al., PRL 88, 137203 (2001)

  5. Questions • Effect of non-equilibrium quasiparticles on magnetization dynamics? • SPIN TRANSFER(Slonczewski) • Spin transfer explains CIMS • Does spin transfer explain LIMT? • No, low carrier fluency in cw • Optical Spin transfer with laser pulses?

  6. Spin transfer Effective field Spin orbit + shape + applied field Quasiparticle spin orientation Magnetization Dynamics: Damping

  7. Initially Recombination or Spin decoherence The transfer !! Photo-carriers/(time volume) Spin Transfer

  8. Anisotropy energy 001 0.015 ] 3 0.010 E [meV/nm 0.005 100 110 0.000 001 110 001 100 Effective Field, magnetic anisotropy Abolfath, et al. PRB (2001) Band structure depends on direction of impurity-spin polarization x=0.055; strain=-0.29%

  9. Optical Spin transfer with laser pulses • Time scales: • Electron precession: 0.1 ps • Recombination: 2-20 ps • Electron Spin decoherence: 5-20 ps • Laser pulse duration: 2-20 ps • Ferromagnetic resonance: 60 ps

  10. Weak pumping: ‘FMR’ z z z x x x Results 1 Energy per pulse: 0.1 mJ/cm2 tL: 3 ps; tR= 2ps, p= n= 1.2 1018 cm3

  11. z z z x x x Strong pumping: Switching My,Mz Mx Energy per pulse: 4.0 mJ/cm2 tL: 3 ps; tR= 2ps, p= n= 5 1019 cm3

  12. K K+Q SPIN WAVE EMISSION Spin relaxation time

  13. Optical Spin transfer allows Laser Controlof magnetization in ferromagnetic (III,Mn)-V Take Home Message E-mail:jfrossier@ua.es Web: www.ua.es/personal/jfrossier

  14. Coherent vs Incoherent Rotation

  15. ALICANTE

  16. Magnetization dynamics under spin injection 1) Current Induced Magnetization Switching in metals Electrical Spin injection CIMS E.B. Myers et al.,Science 285, 867 (1999). 2) Light Induced Magnetization tilt in GaAs:Mn Oiwa et al., PRL 88, 137203 (2001) GaAs:Mn GaAs Optical Spin injection LIMT

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