3-D MICROMAGNETIC MODELING OF DOMAIN CONFIGURATIONS IN SOFT-MAGNETIC MATERIALS

This paper describes a micromagnetic model that computes the vector ma gnetization in a three-dimensional geometry. Since the magnitude of th e magnetization is constant, the energy minimization is performed with respect to polar and azimuthal angles. This generates a pair of coupl ed nonlinear partial differential equations solved numerically in sphe rical coordinates. The demagnetizing field, on the other hand, is not constrained in magnitude and therefore requires three variables at eac h point to fully describe it. Applying this to a Permalloy film whose thickness is equal to one mesh unit permits direct comparison to our 2 -D study that only permitted pure Neel walls to form. The extra degree of freedom allows the magnetic spins to have an out-of-plane componen t, which is especially noticeable in the region where a vortex formed in the 2-D model. This numerical model is being used to study and opti mize the flux conduction in a pipe whose cross section permits the eli mination of closure domains, thus improving both the magnetic suscepti bility and the magnetic stability of the recording head.