In-plane anisotropy in thin-film media: physical origins of orientation ratio

Variations of in-plane magnetic properties are observed in most commercial thin-film media. Magnetic anisotropies of varied origins give rise to preferred orientations quantified by the term orientation ratio (OR). Several mechanisms for in-plane anisotropy have been proposed. Oblique angle of incidence effects from vacuum deposition can lead to the formation of tilted columnar or curved grains resulting in a strong shape anisotropy. The most effort has been involved in understanding 'scratch' anisotropy in textured media where OR develops along texture lines. Mechanisms involving stress, preferred orientation, circumferential alignment of grain c-axes, and radial out of plane c-axis effects have been proposed. Recent experiments and calculations suggest that isotropic media, (OR=1), are superior in signal to media noise, S/N/sub m/, at high recording densities. It is thus important to understand the origin of in-plane anisotropies in thin-film media so as to control them for possible recording property improvements or eliminate them altogether to achieve an isotropic media.