Media noise considerations: Determination of particle noise limit from particulate disk coatings

Studies were made of particulate disk coatings to determine experimentally the particle noise limit. For a coating which has relatively good noise performance, the particulate noise limit is the asymptotic noise value obtained at high written frequencies. For a coating which has relatively poor noise performance, a plot can be made of noise vs. effective defect length (as determined by autocorrelation). The particle noise limit can be taken as the extrapolated noise at zero defect length. In this way the quality of the coating can be judged by the amount of "excess" noise. Noise performance of particulate disk coatings is compared with a thin-film disk.