A Description of Magnetic Switching in Disperse Anisotropy Films

The model of a magnetic film as one domain with a single anisotropy axis is often an inadequate approximation to true film behavior. A better approximation considers the film to consist of many uniaxial regions, with a range of anisotropy constants and of axis orientations in the plane of the film. The dispersion of values results in considerable confusion and awkwardness when using the single domain representation to understand magnetic switching. It is shown here that the total anisotropy distribution can be displayed on a polar plot in which each film region is characterized by a single point with the coordinates: Hk, its anisotropy field, and α, its axis orientation. In this (Hk,α) plane the switching effectiveness of the applied field is represented by a curve which is fixed in size and orientation relative to the field vector. Switching occurs in those parts of the film whose anisotropy points fall within the curve. The field figure is extended to include magnetization reversal by domain wall motion. Inverted switching behavior and switching time measurements are briefly discussed. Interactions between regions are not considered.