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/sub max/) and S/N (to be called S/N/sub 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/sub min/ and S/N/sub min/) in oscillation decrease monotonically with increasing A. The value of A corresponding to the maximum of S/N/sub max/ in a A-S/N/sub max/ curve increases with increasing anisotropy field of a medium and decreases with increasing recording density. The S/sub max/ or S/N/sub max/ in oscillation may correspond to S and S/N of media with small grains or amorphous substances and S/sub min/ or S/N/sub 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/sub k/ could be increased with increasing A.