Rigid disk medium for 20 Gb/in/sup 2/ recording demonstration

A longitudinal medium was developed for 20 Gb/in/sup 2/ recording. This medium has a coercivity of 3380 Oe and M/sub r//spl delta/=0.42 memu/cm/sup 2/. Modulation noise and track edge noise were well suppressed by the decrease in the activation volume. Remanent magnetization is stable; at 338 K, the coefficient of remanence reduction was -0.066 dB/decade in a reverse field of 460 Oe which corresponds to the demagnetizing field in a bit at 430 kFCI. Recording bits of 430 kfci were confirmed by MFM. The BER was 3.45/spl times/10/sup -6/ using a conventional EPR4 channel with a 16/17 code rate at 405 kBPI (430 kFCI). From squeeze measurements, the track pitch was 0.505 /spl mu/m (50.3 ktpi) including a guard band of 0.06 /spl mu/m. 20.4 Gb/in/sup 2/ recording is made possible by the combination of a narrow gap spin-valve head and a low noise medium.