A REPRESENTATIVE HARD SURFACE-LAYER PREPARED AND INVESTIGATED ON A COBALT-SAMARIUM MAGNET

For investigations on the micromagnetic processes on hard magnetic materials it is imperative that the surface grains display the same magnetic hardness as the bulk of the material. In this paper the successful preparation of a nucleation type cobalt-samarium sample (Co5Sm) with bulk coercivity in the surface for high resolution Kerr microscopy by waterfree diamond polishing technique is reported. This fact is proven by domain observations and by comparing hysteresis curves measured by VSM for the bulk and with a transverse optical magnetometer for the surface, Kerr microscopical domain observations on the remagnetizing behaviour at applied fields up to 18 kOe were performed after previous saturation at 26.5 kOe. Of particular interest were the soft spots which remagnetize long before the coercive field is reached. Some examples such as strongly misoriented grains, large grains, grains damaged during polishing, foreign phases etc. are presented. © 1990 IEEE