Phase constituents, magnetic properties, intergranular exchange interactions and transition temperatures of Ge-doped CeFeB alloys

The formation of the paramagnetic CeFe2 phase has deleterious effects on the magnetic properties of Ce-Fe-B type alloys. In order to reduce the volume fraction of the CeFe2 phase and improve the magnetic properties of cost efficient Ce-Fe-B magnetic alloys, Ce17Fe77-xGexB6 (x = 0.0-1.5) alloys were fabricated by melt spinning technique. The crystal structures, magnetic properties, intergranular exchange interactions and phase transition temperatures of CeFe2 and Ce2F14B phases were investigated. The critical amount of Ge doping enhanced the magnetic properties of the alloys by partially decreasing the formation of paramagnetic CeFe2 phase and refining the nano-grains. The optimized magnetic properties of coercivity H-c(j) = 467 kA/m, remanence B-r = 0.51 T and energy density (BH)(max) = 40.6 kJ/m(3) were obtained for Ce17Fe76.4Ge0.6B6 alloy. The analysis of Henkel plots confirmed that the exchange interaction among nano-grains was greatly improved for the optimized doping of Ge. The improved magnetic properties of the investigated alloys are attributed to the refined grains, enhanced intergranular exchange interactions and the decrease of paramagnetic phase for the critical amount of Ge.