Microstructural evolution and the magnetic properties of melt-spun Sm–Co–Cu–B and Sm–Co–Fe–Cu–B ribbons

Abstract An attempt has been made to obtain nanocomposite from Sm–Co–Cu-based alloys. Sm 12 Co 60 Cu 26 B 2 and Sm 16.7 Co 48.3 Fe 25 Cu 8.3 B 1.7 alloys were selected by considering the two-phase region of the Sm–Co–Cu ternary phase diagram and the phase equilibria of Sm–Co–Fe. Sm 12 Co 60 Cu 26 B 2 melt-spun ribbon transformed from TbCu 7 (1:7 H) type to Th 2 Ni 17 (2:17 H)-type phase on annealing at 600 °C for 10 min and exhibited coercivity ( i H c ) of ∼8.0 kOe. Co 23 B 6 precipitates were found either within the grains or at the grain boundary of the hard magnetic phase, and recoil curves in the demagnetization curve indicated exchange coupling between the two phases. Sm 16.7 Co 48.3 Fe 25 Cu 8.3 B 1.7 melt-spun ribbon showed an intermediate value of coercivity ( i H c ∼3–5 kOe). (FeCo)-B precipitates were found at the grain boundaries of SmCo 5 hard magnetic phase.