High density recording on particulate and thin film rigid disks

Current development efforts in small rigid disks (5.25 and 3.5 inch) directed toward achieving linear flux reversal densities in the range of 20-35 kfci (787-1378 fc/mm) are discussed. In conjunction with appropriate encoding, this can yield linear bit densities in the range of 30-50 kbpi (about 1200-200 b/mm). The author compares the write current response at high bit densities and the bit density response of the various small developmental rigid disks in order to determine their relative potential for fulfilling these requirements. It is shown that the performance of the Ba-ferrite disks is comparable to that of the very high coercivity thin-film disks, while the performance of the Co-gamma disks is inferior, particularly with respect to resolution. The typical hysteretic parameters do not explain the observed differences in recording performance. Instead, the authors propose a different set of criteria based on remanence loops, which are expected to correlate much better with the high-density recording characteristics of the media