HIGH-DENSITY RECORDING ON SMCO/CR THIN-FILM MEDIA

SmCo/Cr thin films with coercivity up to 3000 Oe were prepared by rf-diode sputtering. Hard disks were fabricated using glass substrates and the recording properties, carrier to integrated noise ratio, media noise and overwritability were evaluated using conventional thin film inductive heads. The influence of the thickness of the Cr underlayer, SmCo magnetic layer and Cr overlayer on media noise was studied. The intergranular exchange and magnetostatic interaction effects present in SmCo/Cr media were measured from their remanence magnetization curves and correlated to media noise values obtained from recording measurements. The media noise in SmCo/Cr disks varied little with increasing linear density and so supralinear increase in noise as explained by a transition noise model was observed. A thin Cr underlayer (<100 nm) gave the lowest noise SmCo media. An isolated pulse to integrated noise ratio of 44 dB and an overwritability of better than 45 dB were obtained for SmCo/Cr hard disks.