Rare-Earth-Free Iron-Based Permanent Magnets: Progress, Challenges, and Perspectives

Growing demand for secure, sustainable, and affordable magnetic materials has drawn significant attention to rare-earth-free Fe-based permanent magnets. This review integrates recent advances from atomic-scale theory to bulk processing. We first outline the fundamental parameters that govern permanent-magnet performance, such as saturation magnetization (M_s), magnetocrystalline anisotropy, Curie temperature (T_c), and microstructural factors. We then survey four principal material families. The first is Fe–Co alloys whose anisotropy is enhanced through lattice strain and light-element doping. The second is chemically ordered Fe–Ni, tetrataenite, originally discovered in meteorites. The third is nitrogen-rich iron phases typified by α″-Fe₁₆N₂. The fourth is iron phosphides and borides such as Fe₂P and Fe–B. Although calculations predict outstanding magnetic strength, experimental results remain limited by phase instability, grain-size effects, and processing constraints. To bridge this gap, we highlight four complementary research directions: strain engineering, heteroatom doping, deliberate microstructure control, and data-driven ab initio calculations. Coordinated progress in these areas could yield Fe-based magnets with high coercivity and robust magnetization, enabling practical devices for electrified transport, renewable-energy conversion, and compact electronics without costly rare-earth elements.