Investigation of rare earth lean Sm-(Fe,Co)-Mo alloys for permanent magnets

Bulk magnets with the composition of Sm1Fe10.5_xCoxMo1.5 (where x = 0, 1, and 2) with the tetragonal ThMn12 structure were prepared and their intrinsic magnetic properties were studied. The cast samples were then subjected to high-energy-ball-milling (HEBM), followed by hot-compaction at 650 degrees C. The compacted samples were annealed at temperatures ranging from 700 degrees C to 1000 degrees C to obtain high coercivity. The effects of Co on the magnetic properties, including the Curie temperature TC, saturation magnetization MS, anisotropy field HA, and energy product (BH)max were investigated. It is observed that Co substitution increases the Curie temperature, the saturation magnetization, and the remanence, but decreases the anisotropy field and the coercivity. Among the investigated samples, the isotropic Sm1Fe9.5Co1Mo1.5 showed the highest energy product (21.5 kJ/m3) after annealing at 750 degrees C for 48 h, marking a 23 % enhancement relative to our specimen without cobalt substitution.