Local Probing of Magnetization Reversal in Ni–Fe Elliptical Dots With Variable Geometry

We have investigated the detailed magnetization reversal in 10-nm-thick Ni-Fe elliptical dots with several dot sizes using magnetic field sweeping (MFS)-magnetic force microscopy (MFM). At the dot edges, the shape of the phase (the stray field) curve versus magnetic field changes from a stepped hysteresis loop to a almost nonstepped hysteresis loop with increasing dot size. On the other hand, at the center within the dot, sharp or weak decreases in phase are observed as the magnetic field is varied. From these results, it is found that, in the magnetization reversal of a 10-nm-thick Ni-Fe elliptical dot with several dot sizes, the dominant factor changes from the change in the magnetic domain configuration to the domain wall motion as the length of major axis increases.