Crystallization, morphology and magnetic properties of melt-spun (Nd,Pr,Dy)2(Fe,Co,Mo)14B/α-Fe nanocomposites

Crystallization, phase evolution, nanostructure, exchange coupling, and hard magnetic properties of melt-spun Nd_2.4Pr_5.6Dy₁Fe₈₅B₆ and Nd_2.4Pr_5.6Dy₁Fe₇₈Co₆Mo₁B₆ nanocomposites have been studied. All the Nd_2.4Pr_5.6Dy₁Fe₈₅B₆ alloys annealed for 30 s at 565°C or above contain nanostructured α-Fe and Nd₂Fe₁₄B-type (2:14:1) phases, whereas Nd_2.4Pr_5.6Dy₁Fe₇₈Co₆Mo₁B₆ alloys annealed at 600°C or below are mainly composed of α-Fe and a metastable 1:7 phase. A small amount of 2:14:1 phase forms after annealing at 600°C. When annealed at 640°C or above, the hard phase in Nd_2.4Pr_5.6Dy₁Fe₇₈Co₆Mo₁B₆ alloys is the 2:14:1 phase rather than the 1:7 phase. The differences in magnetic properties of the Nd_2.4Pr_5.6Dy₁Fe₈₅B₆ and Nd_2.4Pr_5.6Dy₁Fe₇₈Co₆Mo₁B₆ nanocomposites at different anneal temperatures result from the different nanostructures, exchange coupling and phase components present in the alloys, in particular from the different amount of the 1:7 phase.