Role of pinning in current driven domain wall motion in wires with perpendicular anisotropy

Spatial and time resolved giant magnetoresistance measurements are used to detect thermally activated domain wall (DW) propagation along wires formed from spin valves having perpendicular magnetic anisotropy. We show that field- and current-induced DW propagation are both strongly influenced by the presence of pinning defects. As a result, the creep motion of DWs over macroscopic length scales is found to be stochastic. Only the combination of a high polarized current density and/or magnetic field allows DWs to propagate freely. These results may help explain low current-driven DW velocities observed in previous experiments.