Beneficial effect of Co substitution on the structure and magnetic properties of mechanically alloyed (Pr,Tb)-Fe-(C,B) magnets

The effect of Co substitution on the structure and magnetic properties of mechanically alloyed Pr14Tb2Fe76−xCoxC6B2 and Pr16Fe76−xCoxC6B2 (x=0-20) alloys has been studied systematically. The main phase in the alloys is Pr2Fe14C-type carbide, coexisting with a small amount of α-Fe and rare-earth-rich phases. In addition to the increasing of the Curie temperature of the Pr2Fe14C-type phase, Co substitution can affect the magnetic properties by adjusting the α-Fe fraction of the alloys. The increase of both coercivity and remanence has been realized in a certain composition range. This increase may be attributed mainly to the enhancement of the effective anisotropy constant Keff of the magnets due to the reduced α-Fe fraction with a small Co addition. The highest coercivity iHc of 20.3 kOe and the optimum energy product (BH)max of 10.3 MG Oe have been obtained for the Pr14Tb2Fe69.5Co6.5C6B2 alloy.