Domain wall dynamics in annealed GaMnAs epilayers

4th International School and Conference on Spintronics and Quantum Information Technology (Spintech IV), Maui, HI, JUN 17-22, 2007International audienceWe study magnetic field-driven domain wall motion in a GaMnAs thin film. The velocity is measured as function of the applied field. It varies over 6 orders of magnitude in a field range of 2.5 mT. Two regimes are identified. At low field, the domain wall motion follows a creep regime: it is controlled by defects and the domain wall velocity increases exponentially with the applied field. At higher fields, the domain wall motion follows a depinning regime: pinning defects are less efficient and the wall velocity increases linearly with the field. The highest measured domain wall velocity is 14 ms(-1)