TEM studies of cobalt-rare earth permanent magnets

The microstructures of several cobalt-rare earth magnet alloys from various laboratories were examined by transmission electron microscopy (TEM). The magnets varied in alloying elements and in , the ratio of transition-metal to rare-earth atoms. Matsushita magnets with had a relatively featureless microstructure. Toshiba magnets with contained a fine cellular microstructure, and Brown-Boveri magnets with contained fine isolated precipitates plus a partly-formed cellular structure. These observations are consistent with magnetization hehavior, which indicated nucleation-controlled coercivity for the magnets and pinning-controlled coercivity for the and magnets. Results are compared with earlier TEM studies.