Magnetic reversal under external field and current-driven domain wall motion in (Ga,Mn)As: influence of extrinsic pinning

We investigate the anisotropy of magnetic reversal and current-driven domain wall motion in annealed Ga 0.95 Mn 0.05 As thin films and Hall bar devices with perpendicular magnetic anisotropy. Hall bars with current direction along the [110] and crystallographic axes are studied. The [110] device shows larger coercive field than the device. Strong anisotropy is observed during magnetic reversal between [110]- and -directions. For both devices, the critical current required to depin a domain wall from an etch step is found to be strongly temperature-dependent, and can be described by a power-law dependence on the magnetization ( M ) with an exponent of 2.6±0.3. The domain wall motion is strongly influenced by the presence of local pinning centres.