Demagnetizing Fields in Thin Magnetic Films

The behavior of the magnetization in thin magnetic films of large lateral extent subject to a uniform applied field may be calculated directly from a knowledge of film properties and field strength. The calculation of the behavior of magnetization in the presence of nonuniformity of film properties or of applied field, however, must take into account the demagnetizing field that arises from a local nonuniformity of magnetization. Such a situation occurs in many problems of practical interest. Internally generated fields give rise to a number of effects when nonuniform fields are applied to thin uniaxially anisotropic films.1,2 For example, the hard axis field required for saturation may be several times the anisotropy field and the induced magnetization component may spread to regions where the applied field is very small. The occurrence of such effects in thin films has been considered by Rosenberg3 using a calculus of variations approach and by Kump and Greene4 and Kump 5 using an iterative numerical procedure. More recently Dove and Long0 have shown that there is a simple solution to the nonuniform field problem in the case of nonsaturating spatially periodic applied fields, and have treated localized 1527