Permanent magnets based on 4f-3d compounds

This paper briefly traces the 20-year development history of the magnets that are based on intermetallic compounds of rare-earth and iron-group transition metals. Some fundamental properties that make the 4f-3d alloys useful for permanent magnets are reviewed. The wide variety of practical magnet types, methods for their production and some economic aspects are discussed. Prospects for further development and improvement of these magnets are analyzed in terms of various application requirements.