Abstract: The intermetallic compounds based on the tetragonal ThMn₁₂ prototype crystal structure have exhibited great potential as advanced rare-earth-lean permanent magnets due to their excellent intrinsic magnetic properties. However, the trade-off between the phase stability and the magnetic performance is often encountered in the ThMn₁₂-type magnets. This work was focused on the effects of V doping and nanostructuring on the phase stability and magnetic properties of ThMn₁₂-type Sm-Co-based magnets. Novel SmCo₁₂-based nanocrystalline alloys with the SmCo₁₂ main phase were prepared for the first time. The prepared alloys from the optimal design achieved obviously higher coercivity than the isotropic SmFe₁₂-based alloys, together with comparable performance of other magnetic features. The enhancement in the coercivity was ascribed to the pinning of domain walls by the nanocrystalline grain boundaries and stacking faults. First-principles calculations and magnetic structure analysis disclosed that V substitution can stabilize the SmCo₁₂ lattice and elevate its magnetocrystalline anisotropy. This study provides a new approach to developing stabilized metastable structured rare-earth-lean alloys with high magnetic performance.

Key words: Nanostructuring, Phase stability, SmCo₁₂-based magnets, Coercivity