Fine-particle iron-cobalt magnet achievements in the permanent-magnet industry

Experiences of the past decade in developing and utilizing Fe-Co fine-particle magnets are described. A brief review of theoretical considerations involved and the extent to which theoretical promise has been realized in a commercial process is discussed. The wide range of unit magnetic properties obtained by spacing and ordering the fine-particle building blocks are given. Cold pressing and extrusion-forming techniques have contributed to the many combinations of mechanical and magnetic property variation available. Some of the unique experiences in utilizing fine-particle magnets in magnetic circuits and devices are described. The close magnetic and physical tolerances of fine-particle magnets have had an important impact on the small electromechanical device area. Specific examples of unique designs are described in terms of a small dc motor, a core meter, a hearing aid, and the reed switches.