Recording properties of Co-based alloy heat-treated media

The recording properties of Co-based alloy heat-treated media using carbon substrates with high heat resistance were investigated. For media with the same Hc, the amplitude and media noise of the CoCrTa media were lower than those of CoNiCr and CoCrPt media, because of the lower Brδ (where δ is the thickness of the Co-based alloy layer). For CoNiCr media with the same Brδ, the media noise decreased with increasing Hc, that is, with increasing heat treatment temperature. Analyses of the rotational hysteresis loss using a highly sensitive torque magnetometer and high resolution scanning transmission electron microscopy (HRSTEM) showed that the values of Hc/Hkgrain increased to 0.44 with increasing Hc, and that the Cr concentration at the grain boundaries of the CoNiCr also increased. It is therefore thought that the reduction in noise was achieved as a result of reduced exchange coupling between grains.