Anisotropic SmFe₁₀V₂ Bulk Magnets with Enhanced Coercivity via Ball Milling Process

Anisotropic bulk magnets of ThMn₁₂-type SmFe₁₀V₂ with a high coercivity (H) were successfully fabricated. Powders with varying particle sizes were prepared using the ball milling process, where the particle size was controlled with milling time. A decrease in H occurred in the heat-treated bulk pressed from large-sized powders, while heavy oxidation excessively occurred in small powders, leading to the decomposition of the SmFe₁₀V₂ (1-12) phase. The highest H of 8.9 kOe was achieved with powders ball-milled for 5 h due to the formation of the grain boundary phase. To improve the maximum energy product ((BH)), which is only 2.15 MGOe in the isotropic bulk, anisotropic bulks were prepared using the same powders. The easy alignment direction, confirmed by XRD and EBSD measurements, was <002>. Significant enhancements were observed, with saturation magnetization (M) increasing from 59 to 79 emu/g and a remanence ratio (M/M) of 83.7%. (BH) reaching 7.85 MGOe. For further improvement of magnetic properties, controlling oxidation is essential to form a uniform grain boundary phase and achieve perfect alignment with small grain size.