Giant enhancement of the domain wall velocity in irradiated ultrathin magnetic nanowires

Domain wall velocity measurements in ultrathin Pt/Co(0.6 nm)/Pt narrow magnetic wires with perpendicular anisotropy are reported. Tracks (0.45 and 0.9 microns wide) are defined by drawing twins of parallel etched/irradiated lines with a focused Ga+ beam (FIB). In these films, irradiation induces a large decrease in coercivity due to Co-Pt intermixing at the interfaces, as checked in areas submitted to various fluences. At the same field, the domain wall propagates at far higher velocities in a 0.45 mum track than in the virgin film. It is explained by the calculated irradiation fluence profile. Hence, irradiation can be used to design structures where the magnetic information propagates very rapidly under a small applied field.