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

To decrease the grain size and grain size distribution in longitudinal medi a, a small amount of oxygen exposure onto either normal NiP or Co co-precip itated Co-NiP/Al-alloy substrates has been used, The substrate surfaces of both media were dry-etched by RF-plasma prior to oxygen exposure, The expos ure of 3.5 L of oxygen onto the normal NIP substrate surface reduces the gr ain diameter from 10.0 nm to 8.8 nm while maintaining the standard distribu tion 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 s ubstrate 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.