Magnetization reversal in mesoscopic Ni/sub 80/Fe/sub 20/ wires: a magnetic domain launching device

The magnetization reversal process in mesoscopic permalloy (Ni/sub 80/Fe/sub 20/) wire structures has been investigated using scanning Kerr microscopy, magnetic force microscopy (MFM) and micromagnetic calculations. We find that the junction offers a site for reversed domain wall nucleation in the narrow part of the wires. As a consequence, the switching field is dominated by the domain nucleation field and the junction region initiates reversal by the wall motion following the nucleation of domains. Our results suggest the possibility of designing structures that can be used to "launch" reverse domains in narrow wires within a controlled field range.