Investigation of the body-centred tetragonal structure of Fe–Co–V–N Bulk foils using the rolling and ammonia-gas-nitriding method

Improving the properties of permanent magnets is essential for the advancement of electric motors in reducing energy consumption and carbon emissions. This study investigated the effect of V and N addition to FeCo foils on the stability of tetragonally distorted FeCo-based bulk magnets. The incorporation of these two elements stabilised the body-centred tetragonal structure in thin-film and bulk systems. Fe–Co–V ingots were rolled and nitrided by ammonia gas at 650 °C for 5 h. A body-centred tetragonal lattice with an axial ratio of c/a ≈ 1.1 was observed by transmission electron microscopy, and the collected data suggested the induction of a large uniaxial magnetic anisotropy. This study is expected to improve our understanding of rare-earth-free magnets.