Intrinsic Coupling between Current and Domain Wall Motion in (Ga,Mn)As

We consider current-induced domain wall motion and, the reciprocal process, moving domain wall-induced current. The associated Onsager coefficients are expressed in terms of scattering matrices. Uncommonly, in (Ga,Mn)As, the effective Gilbert damping coefficient alpha(w) and the effective out-of-plane spin-transfer torque parameter beta(w) are dominated by spin-orbit interaction in combination with scattering off the domain wall, and not scattering off extrinsic impurities. Numerical calculations give alpha(w)similar to 0.01 and beta(w)similar to 1 in dirty (Ga,Mn)As. The extraordinarily large beta(w) parameter allows experimental detection of current or voltage induced by domain wall motion in (Ga,Mn)As.