Magnetization reversal in mesoscopic Ni80Fe20 wires: A magnetic domain launching device

The magnetization reversal process in mesoscopic permalloy (Ni80Fe20) wire structures has been investigated using scanning Kerr microscopy, magnetic f orce microscopy (MFM) and micromagnetic calculations, We find that the junc tion offers a site for reversed domain wall nucleation in the narrow part o f the wires. As a consequence, the switching field is dominated by the doma in nucleation field and the junction region initiates reversal by the wall motion following the nucleation of domains, Our results suggest the possibi lity of designing structures that can be used to "launch" reverse domains i n narrow wires within a controlled field range.