Magnetic Properties of Hot-Formed Pr-Fe-Co-B-Cu/.ALPHA.-Fe Type Anisotropic Nanocomposite Magnets

Abstract

Magnetic properties of hot-formed magnets with compositions of Pr 10 Fe (80-x) Co 5 B 5 Cu x (x=0, 1, 3, 5) were investigated. J-H curves parallel and perpendicular to the alignment field direction of a powder sample were measured and J' ratio was calculated in order to determine whether the magnet was isotropic or anisotropic. It was found that the values of J'ratio for Cu-free samples with various hot-forming temperatures were lower than 1.05 and indicated that the magnets were isotropic. This result is similar to that obtained for Nd based Cu-free samples. The J-H curves for Cu-added samples showed anisotropic behavior and the highest value of J'ratio (1.46) was obtained for Pr 10 Fe 77 Co 5 B 5 Cu 3 with hot-formed at 1223 K. This value was higher than that of Nd 10 Fe 77 Co 5 B 5 Cu 3 (J'ratio=1.31). The result of DSC measurement for Pr 10 Fe 77 Co 5 B 5 Cu 3 showed an existence of a phase with melting temperature of 1065 K. A similar phase was observed in Nd 10 Fe 77 Co 5 B 5 Cu 3 , and melting temperature of the phase was 1099 K. It was considered that a reason of the improvement of J'ratio for Pr based sample was due to the decrease in melting temperature of this phase.