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_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