Measurements of the temperature and spatial variations of coercivity in magneto-optic recording media using a scanning laser microscope

A scanning laser microscope was used to obtain images of the spatial variation, on a micron scale, of coercivity in TbFeCo thin film samples with compositions close to the room-temperature compensation composition, which are to be used in magnetooptic recording applications. These images reveal local reductions in coercivity of about 30% in regions surrounding surface defects which are believed to be pinholes in the AlN passivation layer. The dependence of coercivity on the incident laser power, and hence sample temperature, was also observed, the coercivity being seen to reduce by an order of magnitude for a doubling of incident laser power density