Rare-Earth-Free Magnets: Enhancing Magnetic Anisotropy and Spin Exchange Toward High-TC Hf₂MIr₅B₂ (M = Mn, Fe)

Designing new rare-earth-free (REF) permanent magnetic materials (PMM) to replace the high performing but critically restrained rare-earth-based PMM remains a great challenge to the scientific community. Here, we report on the rational design of new REF PMM, Hf₂MIr₅B₂ (M = Fe, Mn) via a theory-experiment combined approach. Density functional theory (DFT) predicted strong interchain M-M spin-exchange coupling and large magnetocrystalline anisotropy energies (EMAE) for the new compounds, suggesting potential intrinsic PMM properties. Subsequent experimental bulk syntheses and magnetic characterizations established the highest ordering temperature (TC ∼ 900 K) for Hf₂FeIr₅B₂ and the highest intrinsic coercivity (HC) value for Hf₂MnIr₅B₂ (HC = 62.1 kA/m) reported to date for Ti₃Co₅B₂-type compounds. Importantly, at room temperature both phases show significant coercivities due to intrinsic factors only, hinting at their huge potential to create REF PMM by improving extrinsic factors such as controlling the microstructure and the domain orientation.