Magnetization reversal in particulate recording media

Magnetization is a material property traced to the spin motion of electrons. Magnetic particles are used in making magnetic tapes and disks for recording media; such particles are suspended in a binder and then painted onto the substrate (a film or a disk). Micromagnetics deals with magnetic phenomena at the “intermediate” scale, which includes such small particles as used in recording media. In micromagnetic phenomena at the scale of 0.01μm to 10μm, domains and domain-walls play a fundamental role in the model; these were described in [1]; the particles which will be considered in the present chapter are smaller, and do not support domain walls. On September 25, 1992 T. R. Hoffend, Jr. from 3M presented ongoing work [2] on micromagnetics based, vector hysteresis model for studying the collective effect of particle interaction and non uniformities on magnetization reversal processes in particulate recording media. The motivation for this work is to understand the link between single particle properties and ensemble properties and, in particular, to investigate the origins of measured differences in the response of various types of particulate recording media. He described the model, consisting of a coupled system of Landau—Lifshitz equations, and then presented some numerical results and posed open problems.