Current-induced domain-wall dynamics is investigated via high-resolution soft x-ray transmission microscopy by a stroboscopic pump-and-probe measurement scheme at a temporal resolution of 200 ps. A $180°$ domain wall in a restoring potential of a permalloy microstructure is displaced from its equilibrium position by nanosecond current pulses leading to oscillations with velocities up to 325 m/s. The motion of the wall is described with an analytical model of a rigid domain wall in a nonharmonic potential allowing one to determine the mass of the domain wall. We show that Oersted fields dominate the domain-wall dynamics in our geometry.

• Received 2 October 2008

DOI:https://doi.org/10.1103/PhysRevB.78.180405