Developing rare-earth free permanent magnet is attracting extensive research efforts for several device applications and other issues. Here, we investigate the temperature-dependent magnetic properties of the Fe4CoSi alloy. The Fe4CoSi alloy shows a high critical temperature of 980 K with perpendicular magnetic anisotropy. At room temperature, it exhibits a magnetization of 1.44 T, anisotropy constant of 0.8 MJ/m3, and a magnetic hardness parameter of 0.75. We obtain the (BH)max of 554 kJ/m3 at 0 K, 410 kJ/m3 at 300 K, and 215 kJ/m3 at 600 K without demagnetization effect. Even with a demagnetization factor of 0.3, the Fe4CoSi alloy still possesses the (BH)max of 268 kJ/m3 at room temperature. The Fe4CoSi exhibits better permanent magnetic properties compared with ferrites and SmCo5. This may imply that the Fe4CoSi alloy can be a potential Fe-based gap permanent magnet between ferrite and Nd-Fe-B (or Sm–Co) at room temperature. © 2024

Keywords: Energy product, Fe₄CoSi alloy, Permanent magnet, Rare-earth-free, VAMPIRE