Cluster Cutting: A Better Understanding of Media Noise in Perpendicular Magnetic Recording

For perpendicular magnetic recording media, integrated media noise power plotted versus linear density typically shows a linear rise at low densities, then plateaus over the mid density range, and sharply rises in a supralinear fashion at very high densities. Various proposed explanations of this behavior have been less than simple and direct. Here we give evidence and theoretical analyses to support the simple idea that granular clusters existing at low densities can be cut into smaller average cluster lengths by write heads having sufficiently high field gradients, thus accounting for the plateau behavior. Not only is the plateau noise behavior explained, along with nonlinear partial erasure, but also a new insight into the nature of noise and granular cluster results.