Media noise reduction in co-based longitudinal media with new Co co-precipitated NiP/A1 substrate

To decrease the grain size and grain size distribution in longitudinal media, a small amount of oxygen exposure onto either normal NiP or Co co-precipitated Co-NiP/Al-alloy substrates has been used. The substrate surfaces of both media were dryetched by RF-plasma prior to oxygen exposure. The exposure of 3.5 L of oxygen onto the normal NiP substrate surface reduces the grain diameter from 10.0 nm to 8.8 nm while maintaining the standard distribution of grain diameter of about 1.4 nm. As the results, the media signal to noise ratio increases by 0.6 dB. By adding 400 ppm of Co into NiP plated substrate and combined with 1.5 L of oxygen exposure, the grain diameter and the standard distribution of grain diameter decrease from 9.2 nm to 8.3 nm. As the results, the media signal to noise ratio increases by 1.0 dB.