Ultra-Low Noise Properties of Co-Pt and SiO₂ Granular Magnetic Recording Media

The disk characteristics of granular media comprising Co-Pt and SiO2 have been examined to demonstrate their high-density recording capabilities. The grain size increased when RF-bias was applied during sputtering. A coercivity was 2 kOe at a magnetic moment (Mrt) of 0.4 memu/cm2 and a Co-Pt content of 50vol.% when a Cr seed layer used. The mean grain size was less than 10 nm and the grains were thoroughly isolated in the SiO2 matrix. The normalized media noise was less than 10-2μm1/2μVrms/μVpp up to 200 kfci. Transition patterns of more than 200 kfci were clear at a track-width of 1μm. The surface roughness was similar to that of a bare glass substrate. No degradation in magnetic properties was observed after 1000 hrs. in an 80°C-75%R.H. environment.