COMPOSITION EFFECTS ON RECORDING PROPERTIES OF COPTCR THIN-FILM MEDIA

The effects of different composition of CoPtCr thin-film media on macromagnetic and recording parameters have been studied. Increasing Cr percentage in the magnetic alloy drops M(5), and consequently M(r) for films of similar squareness, requiring a greater thickness value to achieve the same M(r) delta product. Resolution at high recording densities degrades with higher M(r) delta as expected. For fixed M(r) delta, resolution drops with the higher delta values as predicted by the thickness loss factor in the Wallace equation. Low M(r) high delta films have worse resolution, but an improvement in media noise is noted. It could be argued that this results from greater exchange decoupling from higher intergranular Cr concentrations in the high Cr content, low M(r) alloys. It is speculated here that the noise reduction results from the lower magnetostatic interactions in the film from the decreased value of M(5). Recording densities and head-medium spacings have reached a point where the thin-film media thickness can become a significant loss factor for the short wavelength signals. Thus, the media design must be a compromise for noise and short wavelength amplitude.