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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, Hf 2 M Ir 5 B 2 ( 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 ( E MAE ) for the new compounds, suggesting potential intrinsic PMM properties. Subsequent experimental bulk syntheses and magnetic characterizations established the highest ordering temperature ( T C ∼ 900 K) for Hf 2 FeIr 5 B 2 and the highest intrinsic coercivity ( H C ) value for Hf 2 MnIr 5 B 2 ( H C = 62.1 kA/m) reported to date for Ti 3 Co 5 B 2 -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.

Two different boron layers, flat (graphene-like) and puckered (phosphorene-like), found in the crystal structure of Mo 2 B 4 show drastically different activities for hydrogen evolution, according to Gibbs free energy calculations of H-adsorption on Mo 2 B 4 . The graphene-like B layer is highly active, whereas the phosphorene-like B layer performs very poorly for hydrogen evolution. A new Sn-flux synthesis permits the rapid single-phase synthesis of Mo 2 B 4 , and electrochemical analyses show that it is one of the best hydrogen evolution reaction active bulk materials with good long-term cycle stability under acidic conditions. Mo 2 B 4 compensates its smaller density of active sites if compared with highly active bulk MoB 2 (which contains only the more active graphene-like boron layers) by a 5-times increase of its surface area.