High-speed photography of topological switching and anisotropic saturation velocities in a misoriented garnet film

Abstract

The topological switching of a bubble array into one of the opposite polarity by a bias field pulse is studied in a garnet film by high-speed photography. The key requirement for regular switching is found to be an anisotropic wall velocity which causes the expanding bubbles to make contact with only four out of six of the nearest neighbours. The same anisotropy of almost 2:1 in the saturation velocity is also observed in isolated bubbles pulsed to expand. The velocity anisotropy and the static bubble ellipticity are related to a 2.2 degrees misorientation of the film's (111)-axis from the surface normal, which gives rise to an in-plane magnetic anisotropy.