Nd-Fe-B/Sm-M/Nd-M (M = Fe, Co, Ti, Cu, Zr) hybrid magnets with improved thermal stability

Abstract Hybrid magnets of Nd 12 Fe 82 B 6 (2:14:1-phase)/Nd 9.4 Fe 59 Co 25.3 Ti 6.3 (3:29-phase) and Nd 12 Fe 82 B 6 /Sm 11.1 Co 65.8 Fe 8.9 Cu 10.7 Zr 3.5 (2:17-phase) with different weight ratio have been prepared by spark plasma sintering pressing technique from ball-milled powders obtained from melt-spun ribbons. Influence of the ratio between the two phases on the magnetic properties and thermal stability of the hybrid magnets was studied. It has been found that the ratio has a remarkable influence, especially on the thermal stability of the bulk magnets. However, the magnetic properties of such type of hybrid magnets result not only from the type and ratio of components but also from the interaction between them. It was found that in NdFeB/3:29 hybrid magnets with 15% content of 3:29-phase, the temperature coefficients of remanence (α) and of coercivity (β) are improved from −0.095 to −0.082 (%/°C) and from −0.57 to −0.47 (%/°C), respectively, as compared to the Nd 2 Fe 14 B single-phase counterpart. While for the NdFeB/2:17 hybrid magnets the content of 2:17-phase is not significantly influencing the temperature coefficient of induction (α), the temperature coefficient of °C (β) increases up to −0.41 (%/°C) for 10% content of 2:17-phase. The increase in the reversible temperature coefficients of hybrid magnets indicate a remarkable improvement of their thermal stability.