Coercivity enhancement of a Ce-based permanent magnet by grain boundary diffusion with Re70Cu30 (Re: Nd/Dy) eutectic alloys

Nd70Cu30 and Dy70Cu30 eutectic alloys have been used for the grain boundary diffusion process (GBDP) of a Ce-based permanent magnet, respectively. The coercivity increments (∼200 kA/m, 35%) are almost the same after GBDP in spite of the different diffusion sources. The thermal stabilities of remanence and coercivty of the magnet after GBDP with Nd70Cu30 alloy are much higher than that of the magnet after GBDP with Dy70Cu30 alloy. Continuous grain boundary phase was observed for the magnet after GBDP with Nd70Cu30 alloy while the grain boundary phase was less continuous for the magnet after GBDP with Dy70Cu30 alloy. The results indicate that Nd70Cu30 alloy is a promising diffusion source to improve the magnetic properties of Ce-based permanent magnets.