Thickness and roughness dependence of DC modulation noise in thin film magnetic recording disk media

DC modulation noise was studied as a function of magnetic-layer thickness and surface roughness for longitudinal, low-noise, nominally 1000-Oe, plated CoP and CoNiZnP, thin-film magnetic recording disk media made from controlled fabrication runs. DC modulation noise is generated when a reverse longitudinal DC field is applied to a uniformly magnetized disk. A model which allows autocorrelation functions and noise spectra to be calculated and which agrees with measured noise data (with correlations greater than 0.99) was developed. Trends observed with measured data and the model indicate that inhomogeneities in the medium, and not surface roughness, are the dominant sources of noise