Post on 21-Dec-2015
Optical spin transfer in GaAs:Mn Joaquin Fernandez-Rossier,
Department of Applied Physics, University of Alicante (SPAIN)
CECAM June 2003, Lyon (FR)
cond-mat/0304492
andA. Núñez , M. Abolfath and A. H. MacDonald
Department of Physics, University of Texas at Austin
•Optical control of magnetization dynamics •Optical injection of electrons and holes in GaAs:Mnwith spin perpendicular to magnetization•Spin transfer in GaAs:Mn
Main Ideas
Current Induced Magnetization
Switching (CIMS)
E.B. Myers et al.,Science 285, 867 (1999).
Current
Magnetization dynamics under electrical spin injection
Co Cu Co
Oiwa et al., PRL 88, 137203 (2001)
Magnetization dynamics under c.w. optical spin injection
GaAs(Ga,Mn)As GaAs
Light Induced Magnetization tilt (LIMT)
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?
)( HM
Hdt
d
s
Magnetization Dynamics:
Damping
][E
H
Spin orbit + shape + applied field
Effective field
))((
ntPM s
B
Spin transfer
Quasiparticle spin orientation
Spin Transfer
n
Initiallyn
Recombination orSpin decoherence
The transfer !!
))((
ntPMdt
d
s
B
ST
Photo-carriers/(time volume)
Abolfath, et al. PRB (2001)
Band structure depends on direction of impurity-spin polarization
001
100 110
Anisotropy energy
E [m
eV/n
m3 ]
0.000
0.005
0.010
0.015
001 100 110 001
Effective Field, magnetic anisotropy
][E
H
x=0.055; strain=-0.29%
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
Optical Spin transfer with laser pulses
Results 1
Energy per pulse: 0.1 mJ/cm2
tL: 3 ps; tR= 2ps, p= n= 1.2 1018 cm3
Weak pumping: ‘FMR’
z
x
z
xz
x
My,Mz
Mx
Energy per pulse: 4.0 mJ/cm2
tL: 3 ps; tR= 2ps, p= n= 5 1019 cm3
z
x
Strong pumping: Switching
z
x
z
x
Take Home Message
Optical Spin transfer allows Laser Control of magnetization in
ferromagnetic (III,Mn)-V
E-mail:jfrossier@ua.esWeb: www.ua.es/personal/jfrossier