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 Ga0.95Mn0.05As thin films and Hall bar devices with perpendicular magnetic anisotropy. Hall bars with current direction along the [110] and [1 (1) over bar0]crystallographic axes are studied. The [110] device shows larger coercive field than the [1 (1) over bar0] device. Strong anisotropy is observed during magnetic reversal between [110]- and [1 (1) over bar0]-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.