Investigations of magnetic properties and microstructure of 40Cedidymium–Fe–B based magnets

The influence of Si, Co, and Dy2O3 on magnetic properties of sintered 40Cedidymium–Fe–B magnets was investigated and related to the microstructure through transmission electron microscopy (TEM) investigations. It is found that the decrease in iHc and Tc caused by the presence of Ce in the 40Cedidymium could partly be compensated by additives. Sintered magnets with iHc = 9.2 kOe and (BH)max=28.2 MG Oe were successfully achieved. TEM investigations show an intragranular amorphous phase within the R2Fe14B (R=Nd, Pr, or Ce) grains and three new intergranular phases at grain boundaries and junctions of the R2Fe14B grains. It is suggested that the deterioration in the magnetic hardening is closely related to these new phases as well as the low magnetic anisotropy field of the Ce2Fe14B compound. The intragranular phase is likely to act as nucleation positions for reverse magnetic domains.