A representative hard surface layer prepared and investigated on a cobalt-samarium magnet

The successful preparation of a nucleation-type cobalt-samarium sample (Co₅Sm) with bulk coercivity in the surface for high-resolution Kerr microscopy by the water-free diamond polishing technique is reported. The surface coercivity value is proven by domain observations and by comparing hysteresis curves measured by VSM (vibrating sample magnetometry) for the bulk of the material and with a transverse optical magnetometer for the surface. Kerr microscopic domain observations on the remagnetizing behavior 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, and foreign phases, are presented