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_s, and consequently M_r for films of similar squareness, requiring a greater thickness value to achieve the same M_r δ product. Resolution at high recording densities degrades with higher M_rδ as expected. For fixed M _rδ, resolution drops with the higher δ values as predicted by the thickness loss factor in the Wallace equation. Low M_r high δ 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 that the noise reduction results from the lower magnetostatic interactions in the film from the decreased value of M_s. 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