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

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journal contribution
posted on 10.03.2021, 01:43 by Pritam Shankhari, Oliver Janka, Rainer Pöttgen, Boniface P. T. Fokwa
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.