Research and Development of Bulk Anisotropic Nanograin Composite Rare Earth Permanent Magnets

Innovative and cost-effective technology for synthesizing bulk anisotropic nanograin composite rare earth magnets has been developed. Using a powder blending technique, (BH)max of nanograin composite magnets can reach 40 to 50 MGOe, while applying powder coating techniques, (BH)max = 45–55 MGOe were achieved. Thus, principal technical difficulties in synthesizing bulk anisotropic nanograin composite magnets are successfully overcome. In addition, it was observed that the magnetically soft phase in a composite magnet could be up to tens of micrometers, or more than 1000 times larger than the upper size limit predicted by the current models of interface exchange coupling, which indicates that further reducing the size of the soft phase and improving its distribution will significantly improve the magnetic performance of nanograin composite magnets.