Influence of Ho spontaneous aggregation on the coercivity and magnetic domain movement of sintered NdY-Fe-B magnets.

Development of NdY-Fe-B magnets not only reduces the cost of Nd-Fe-B type magnets but also promotes the balanced utilization of rare-earth resources. However, the lower coercivity of NdY-Fe-B magnets hinders their further development. This study investigated the coercivity of NdY-Fe-B magnets via intergranular doping of Ho 76 Al 12 Ga 12 powders. Although this process improved the coercivity, the remanence substantially deteriorated with the increasing content of the Ho 76 Al 12 Ga 12 alloy. A coercivity of 1.37 T was achieved in a NdY-Fe-B magnet with a Ho 76 Al 12 Ga 12 alloy doping of 7 wt%, showing a coercivity increment (Δ H cj) of 0.64 T compared to the original magnet. This can be attributed to the observed microstructural and elemental distributions, as well as the analysis of the magnetic domain wall movement. An abnormal Ho-biased layer is observed between the Y-rich core and the Ho-rich shell in the matrix grains, exhibiting a higher anisotropy field compared than the shell layer. Further analysis revealed that the movement of magnetic domain wall movement was obstructed by the Ho-biased layer, demonstrating a domain-wall pinning effect within the matrix grains. Additionally, the formation of a Ho-rich shell in the outer area of the 2:14:1 matrix grain and the presence of a continuous uniform grain boundary phase were found to be important for improving both coercivity and thermal stability. • The coercivity of NdY-Fe-B magnets have been improved by intergranular doping of Ho 76 Al 12 Ga 12 powders. • An abnormal Ho biased layer is observed between the Y-rich core and Ho-rich shell in the matrix grains. • The magnetic domain wall is obstructed by Ho-biased layer, which is considered to the reason for coercivity improvement. [ABSTRACT FROM AUTHOR]