Spin transfer and spin-orbit torques in in-plane magnetized (Ga,Mn)As tracks

Current-driven domain wall motion is investigated experimentally in in-plane magnetized (Ga,Mn)As tracks. The wall dynamics is found to differ in two important ways with respect to perpendicularly magnetized (Ga,Mn)As: the wall mobilities are up to ten times higher and the walls move in the same direction as the hole current. We demonstrate that these observations cannot be explained by spin-orbit field torques (Rashba and Dresselhaus types) but are consistent with nonadiabatic spin transfer torque enhanced by the strong spin-orbit coupling of (Ga,Mn)As. This mechanism opens the way to domain wall motion driven by bulk rather than interfacial spin-orbit coupling as in ultrathin ferromagnet/heavy metal multilayers.