Thermal relaxation of the magnetization in recording media

The time dependence of materials for magnetic recording media, both particl es and thin films, is studied. The stability, as deduced from the magnetiza tion decay, magnetic viscosity and fluctuation field, is greater in undoped materials with good morphological and structural order. The activation vol ume is smaller than the physical size in all the particulate materials, and related to the magnetization switching: it shows relative decrease when th e reversal does not take place by coherent rotation, as it occurs in doped particles, or when the particles are composed of segregated sub-units. (C) 1999 Elsevier Science B.V. All rights reserved.