Effect of exchange interaction between grains on R/W properties of single-layer perpendicular recording media

The effect of exchange interaction A between grains on signal (S) and signal-to-noise (S/N) ratio of single-layer perpendicular recording media was investigated by computer simulation. Oscillation of S and S/N, which could be due to the model of the media, was observed with variation of head field. The maximum values of S (to be called S_max) and S/N (to be called S/N_max) in oscillation increase with increasing A in a small A range, saturate and decrease in a large A range. On the other hand, the minimum S and minimum S/N (to be called S_min and S/N_min) in oscillation decrease monotonically with increasing A. The value of A corresponding to the maximum of S/N_max in a A-S/N_max curve increases with increasing anisotropy field of a medium and decreases with increasing recording density. The S_max or S/N_max in oscillation may correspond to S and S/N of media with small grains or amorphous substances and S_min or S/N_min may correspond to S and S/N of media with large grains, respectively. Therefore, S and S/N of the media composed of small grains or amorphous substances with high H_k could be increased with increasing A.