Microstructural evolution and magnetic properties of spark plasma sintered SmCo5 and SmCo5-Fe composites

Optimizing SmCo 5 -based nanocomposites for high-temperature magnetic applications requires balancing coercivity and saturation magnetization, properties often compromised by grain coarsening, oxidation, and secondary phase formation during conventional sintering. This study investigates the microstructural evolution and magnetic properties of SmCo 5 and SmCo 5 -Fe composites processed via high-energy ball milling followed by spark plasma sintering at 900 °C and 1000 °C, a route designed to retain the nanostructure while enabling rapid densification compared to conventional sintering. A suite of characterization techniques, including electron microscopy, X-ray diffraction, magnetometry, Magneto-optical Kerr effect, and magnetic force microscopy, reveals the extent of consolidation, phase composition, and change in magnetic response due to the presence of different phases such as SmCo 5 , Sm 2 Co 17 , Sm 2 O 3 , and CoFe. SmCo 5 sintered at 900 °C exhibits a coercivity of 37.4 kOe and saturation magnetization of 77.2 emu/g, with phase fractions of ~64% SmCo 5 (hard phase, H c ≈ 44 kOe) and ~36% Sm 2 Co 17 (soft phase, H c ≈ 7.5 kOe). At 1000 °C, coercivity increased slightly to 38.0 kOe while magnetization decreased to 71.1 emu/g, with ~65% SmCo 5 (H c ≈ 45 kOe) and ~35% Sm 2 Co 17 (H c ≈ 5.5 kOe). Fe addition promoted CoFe phase formation, raising magnetization to 133 emu/g, but reducing coercivity to ~45-80 Oe. These results highlight the role of Fe in tuning magnetic interactions and emphasize the strong influence of processing temperature in controlling phase evolution, which could offer a pathway to optimize SmCo 5 -based nanocomposites for high-temperature magnetic applications. • SmCo 5 and SmCo 5 -Fe were synthesized by ball milling and spark plasma sintering. • Sintering temperature controls Sm 2 Co 17 and Sm 2 O 3 phase formation in SmCo 5 magnets. • Fe addition forms CoFe, increasing saturation magnetization but lowering coercivity. • TEM and MFM reveal nanoscale phase distribution and magnetic heterogeneity. • Exchange coupling not achieved due to undesirable extensive phase transformation.