In recent years, with the rapid spread of electric vehicles toward the realization of carbon neutrality, the demand for permanent magnets in in-vehicle motors has increased, and the development of next-generation ferromagnetic materials for permanent magnets has been actively promoted. Ferromagnetic materials used for permanent magnets are required to have a high saturation magnetization (M_s), large uniaxial magnetic anisotropy energy (K_u), and large coercivity. However, most ferromagnetic materials with a large K_u contain rare earth or precious metal elements, so it is desirable to develop ferromagnetic materials that do not contain them in order to achieve a sustainable society. To meet that demand, we have focused on the L1_0-type ordered FeNi alloy (L1_0-FeNi) as a high M_s and large K_u material for a new permanent magnet material. Regarding this topic, we would like to introduce recent progress on the synthesis of L1_0-FeNi films and powder using a topotactic denitriding method to FeNiN and show the possibility of applying L1_0-FeNi to permanent magnets.
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