Dependence of coercivity ratio on anisotropy distribution and interactions in particulate media

Abstract

Summary form only given. The distribution of anisotropy energies is an important consideration in the performance of high-density recording media. Particles with very small anisotropy energies will be thermally unstable and particles with very large anisotropy energies may not be switchable. It was recently shown that large anisotropy distributions exist in L1/sub 0/ materials with partial chemical ordering, including FePt nanoparticles and CoPt/SiO/sub 2/ multilayer films. It was also observed that these partially ordered materials have large remanent to ordinary coercivity ratios that may be related in part to the anisotropy distribution. We have calculated the dependence of the coercivity ratio on the anisotropy distribution width and examined the effect of interactions on this dependence. The effect of both anisotropy distribution and mean field interaction parameter on the width of the irreversible susceptibility versus field curve was also calculated. These results suggest that the coercivity ratio can be a useful parameter for estimating anisotropy distribution widths in granular systems with weak interactions.