Kerr magnetooptic study of slow to intermediate speed propagation phenomena in thin Ni-Fe films

Evidence of high-speed propagation phenomena has been previously cited as a possible mechanism for slow to intermediate speed switching. Quasi-static Kerr magnetooptical observation of propagation phenomena for applied fields and total switching times well into the region of "incoherent rotation" has resulted in a more complete and quantitative description of these effects. The ability of the quasi-static procedure to predict the results of uninterrupted dynamic flux reversal is demonstrated. In particular, for applied easy-axis field Hswell above coercive field Hcbut below the anisotropy field Hk, a pair of "zigzag walls" composed of connected domain tips extended in the hard direction is observed to switch approximately 100 percent of the film by longitudinal motion. For threshold fields near the theoretical astroid value, well-defined propagation fronts have been observed and their velocities carefully measured. Finally, the resulting velocity-field data are used to predict with good accuracy the results of experiments on uninterrupted reversal under a ramp field for up to Oe/s.