Materials properties and utilization of Fe3B/Nd2Fe14B-type nanocomposite permanent magnets based on Nd-Fe-Cr-Co-B

Recent progresses of materials development and their utilization of Cr-and-Co-doped Fe3B/Nd2Fe14B-type nanocomposite permanent magnets are reported. A practical balance between enhanced intrinsic coercivity and temperature stability of magnetic properties has been realized by simultaneous additions of Cr and Co. This type of magnets are less susceptible to oxidation because of the less rare-earth content. Consequently, even fine powders (e. g., under 38 micrometer sieve) are physically and chemically stable in contrast to the conventional Nd2Fe14B-type melt-spun materials. The stability in terms of the structural losses is also superior to that of the Nd2Fe14B-type melt-spun materials. Utilization of the Cr-and-Co-doped Fe3B/Nd2Fe14B nanocomposite permanent magnets as a hard magnetic component of injection-molded resin-bonded magnets seems promising because of the excellent stability of the magnetic properties of fine powders. Direct quenching of a melt into the nanocomposite structure has become possible recently in addition to the conventional processing route of crystallization of an amorphous precursor, opening up the possibility of less-expensive production of the material.