Effects of underlayer and substrate texture on magnetic properties and microstructure of a recording medium

The dependence of magnetic properties and microstructure of a sputtered thin film medium for high-density longitudinal recording on a Cr underlayer and circumferential substrate texture has been studied. The combined use of the underlayer and substrate texture induces circumferential anistropic magnetic properties in the medium. In the media without and with the underlayer on textured substrates, the dominant planes lying in the film surface are Co hcp {0002} and {01 1 1}, respectively. Grain boundary matching between the medium and the underlayer, as observed by cross-sectional transmission electron microscopy (TEM), indicates that the medium grows by replicating columnar grains in the underlayer. With this replication, grains in the medium with the underlayer are much larger than those in the medium without the underlayer. The circumferential anisotropy occurs only when the grain diameter of the medium is of the same physical size as the surface roughness and the grain boundaries are aligned by the substrate texture.