Domain Walls Dynamics in
(Ga,Mn)As
1 Laboratory
for Nanoelectronics and Spintronics, Research Institute of Electrical
Communication
2 ERATO Semiconductor
Spin-polarized current induced domain wall (DW) motion reveals rich physics resulting from the interaction between spin-polarized conduction electrons and localized spins in a DW. By using a 30 nm thick, 5 mm wide (Ga,Mn)As stripe (xMn = 0.045) having a perpendicular magnetic anisotropy, we determined the DW velocity (v) versus current density (j) curves with the sample temperature as a parameter using magneto-optical Kerr microscopy. Two regimes in the v-j characteristics are shown to exist. At high-current densities (> 2 x 105 A/cm2), the domain wall velocity was a linear function of the current density above a threshold [1, 2]. At low-current densities, the functional form of the velocity-current curves turned out to be more complex, following a non-trivial empirical scaling law similar to the one observed previously in the magnetic-field driven creep motion in magnetic metals. The former regime is well described by spin-transfer theories, indicating that spin-transfer from the spin-polarized conduction carriers to the localized spins was taking place. Examination of the latter regime and comparison with the magnetic-field driven creep measured on the same (Ga,Mn)As sample has revealed that both follow similar scaling laws but with different scaling exponents, indicating that the two drives, the spin-current drive and the magnetic-field drive, act on DW in fundamentally different ways belonging to two different universality classes.
Acknowledgement: Work done with M.
Yamanouchi, D. Chiba, F.
References:
[1]
M. Yamanouchi, D.
[2]
M. Yamanouchi, D.
[3] M. Yamanouchi, J. Ieda, F.