Current induced domain wall motion in out-of-plane magnetized magnetic nanowires characterized by high resolution magnetic imaging

Current driven domain motion (CIDM) in perpendicularly magnetized multilayers attracts currently much interest due to the simple and narrow Bloch DWs observed in these materials and the more efficient spin transfer compared to previously studied in-plane magnetized permalloy nanowires. Here we report on current induced DW propagation in promising out-of-plane magnetized materials, such as low coercivity (CoFeB(0.6 nm)/Pt) n multilayers and highly spin polarized (Co/Ni)n multilayers. Current-induced magnetization switching was studied in these materials for the first time by high resolution magnetic imaging using XMCD-PEEM. In (CoFeB(0.6 nm)/Pt)n, for wide wires (2 μm) and/or high current densities, current induced domain nucleation is observed. The analysis of the domain patterns indicate that the Oersted field plays a major role in the domain nucleation. In particular, the domain structure can be reversibly switched from one domain configuration to another by current by the sole effect of the Oersted field. For smaller wire width and lower current, current induced DW motion is observed and the interplay between Oe field and spin torque results in a strongly geometry-dependent behaviour.