Nanosecond Photographs of 90°–180° Switching in Biaxial Epitaxial Magnetic Thin Films

Abstract

Flux reversal in epitaxial Ni–Fe thin films has been studied with use of a 10‐nsec exposure time Kerr magneto‐optic camera. The epitaxial films exhibit biaxial anisotropy and both 90° and 180° switching may occur. When the switching field is applied antiparallel to the saturated magnetization, the switching processes are similar to the corresponding processes in polycrystalline films. When the field is applied at an obtuse angle to the saturated magnetization, stripe‐like domains form that lie along the hard axis (45° to easy axes). With very low‐drive fields the boundaries between stripes are 90° walls, but with higher fields the wall angle is much smaller, and the stripes appear like a large amplitude, large wavelength ripple. If the field is applied at an angle greater than 135° to the saturated magnetization, 180° domains nucleate and complete the switching after the stripes form. With angles less than 135°, the switching is completed by the formation of additional stripes and the rotation of the magnetization in nonswitched stripes.