Coercivity enhancement in (Ce,Nd)-Fe-B sintered magnets prepared by adding NdH_x powders

(Ce,Nd)-Fe-B sintered magnets were prepared by the addition of NdH_x powders in Ce₉Nd_4.5Fe₈₀B_6.5 powders. The coercivity is rather low in Ce₉Nd_4.5Fe₈₀B_6.5 magnets, and Ce element prefers to distribute at the outer-layer of main phase (Ce,Nd)₂Fe₁₄B. The investigation of scanning electron microscope shows that the addition of NdH_x powders leads to the increase of Nd content at grain outer-layer of main phase owing to the element diffusion. Magnetization reversal undergoes the nucleation of reversed domain wall at grain outer-later, and the addition of NdH_x powders leads to the increase in the nucleation field of reversed domain, giving rise to the significant improvement of coercivity. The larger amount addition of NdH_x powders leads to the increase in the amount of intergranular phase, resulting in the decreases of the remanence, the squareness of demagnetization curve and the maximum energy product.