Grain boundary construction and properties enhancement for hot deformed (Ce,La,Y)-Fe-B magnet by a two-step diffusion process

The rare earth-iron-boron magnets based on high abundance rare earths (REs) show potential for costeffective permanent magnets but their hard magnetic properties have to be greatly improved. The grain boundary diffusion process (GBDP) is known as an effective way to improve the coercivity of Nd-Fe-B magnets, however, the conventional diffusion method faces a challenge for Ce-based magnets since there is no enough continuous GB layer as the diffusion channel. Here, a two-step (Nd-Cu doping followed by Nd-Cu diffusion) GBDP was introduced for hot deformed (Ce,La,Y)-Fe-B magnet, and the excellent magnetic properties of & mu;0 H c = 0.63 T, & mu;0 M r = 0.68 T, and (BH) max = 72.4 kJ/m 3 were achieved. The Nd-Cu doping helps the formation of RE-rich GB layer, and then it acts as the diffusion channel for increasing the efficiency of the subsequent Nd-Cu diffusion and results in the increased volume fraction of continuously distributed GB phase, whose paramagnetism was verified by 57 Fe Mossbauer spectrometry. Those paramagnetic GB phases help to form the discontinuous domain walls, as observed by Lorentz transmission electron microscopy, and break the magnetic exchange coupling of RE 2 Fe 14 B grains. It thus contributes to the coercivity enhancement of the hot deformed magnet with two-step diffusion, which is further proved by micromagnetic simulation. This study proposes a potential technique to prepare anisotropic hot deformed (Ce,La,Y)-Fe-B magnet with high cost-performance.& COPY; 2023 Published by Elsevier Ltd on behalf of The editorial office of Journal of Materials Science & Technology.

Automated summary

This article introduces a new method to improve the magnetic properties of rare earth-iron-boron magnets. By using a two-step grain boundary diffusion process, a magnet with excellent magnetic properties was obtained. The formation of RE-rich grain boundary layer through doping and diffusion was found to contribute to the enhancement of coercivity, supported by differential scanning calorimetry and transmission electron microscopy.