Degradation Process Due to Multiple Erasing in Pt/Co Magneto-Optical Disks

The degradation process in Pt/Co magnetooptic disks due to repeated erasing was studied by measuring the magnetic properties of the degraded region and by observing deformation of the substrate. The media noise was found to increase starting at a lower number of erase cycles than was needed to effect a decrease in the carrier level. The increase in media noise is attributed to the decrease in perpendicular magnetic anisotropy (K
u
) of the Pt/Co multilayer film. The decrease in carrier level is attributed to a reduction in the residual Kerr rotation due to a further decrease in K
u
, and to deformation of the substrate.