OBSERVATION OF A CURRENT-INDUCED FORCE ON BLOCH LINES IN NI-FE THIN-FILMS

Finite displacements of Bloch lines, induced by current pulses directly traversing the sample, have been observed by the ferrofluid technique in Ni 81Fe19 films of thickness 33-68 nm containing cross-tie domain walls. The pulses of duration ≤ 1 μs are normal to the wall. Bloch lines move along the wall whenever the current density exceeds a critical value ≊1×1012 A/m2. It is possible to partly control the sense of the central spin of Bloch lines by applying a field μ0H≊100 μT normal to the film during Bloch-line creation. The sense of the current-induced force on Bloch lines is found to depend on the sense of the central spin of Bloch lines, and agrees with the sense of the theoretically predicted s-d gyroscopic force which arises from s-d exchange. However, the average value of the force is about four times smaller than the predicted value for a one-band model.