Improvement of coercivity and thermal stability of anisotropic Nd13Fe79.4B7Nb0.3Ga0.3 powders by diffusion of Pr-Cu alloys

Highly anisotropic Nd13Fe79.4B7Nb0.3Ga0.3 powders from a self-organized rod-like disproportionation microstructure and room temperature magnetic properties of μ0Mr = 1.4 T, iHc = 13 kOe, and (BH)max = 41 MGOe are obtained by optimizing hydrogenation disproportionation desorption recombination (HDDR) process. Diffusion of Pr68Cu32 alloy into the HDDR powders further increases the coercivity of the powders to 18 kOe. This enhancement in coercivity is mainly attributed to the modification of grain boundaries including the decrease of Fe content and the increase of boundary thickness. The modified boundaries can work as effective pinning layers for domain walls. The thermal stability of magnetic properties of HDDR powders is also improved after the diffusion treatment.