Study on magnetic properties and demagnetization process of the c-plane in the grain boundary diffusion magnet

Grain boundary diffusion (GBD) can effectively increase the coercivity of sintered Nd-Fe-B magnets. Tb is deposited in the specific areas of the c-plane rather than the entire c-plane to reduce the amount of heavy rare earth elements. In this work, we investigate the magnetic properties and demagnetization process of the c-plane using experimentation and micromagnetic simulation. The c-plane is divided into the center area without Tb deposition and the edge area with Tb deposition. According to the results of the experiment and micromagnetic simulation, it has been found that diffusion on the edge area can decrease the amount of Tb by 58% and increase the contribution of Tb to coercivity (Delta Hcj/wt.% Tb) to 20.55 kOe/wt.%. Compared to the other areas on the cplane, diffusing on the edge area offers the vast majority of Hcj for the GBD and has the highest Delta Hcj/wt.% Tb. Diffusing a small amount of Tb onto the center area can supplement the remaining Hcj. Micromagnetic simulation and Magneto-optical Kerr microscopy are used to study the differences in magnetic properties among different areas on the c-plane by simulating the demagnetization process. Because the edge area is more likely to be demagnetized than the center area, the diffusion of Tb in the edge area can significantly strengthen Hcj.