Phase stability and magnetic properties of RE₂Fe₁₄C system with B substitution: a theoretical investigation

Developing heavy-rare-earth-free permanent magnets with high coercivity based on the RE₂Fe₁₄C system is a promising approach to alleviate the resource risk in this field. The long-standing issue of phase stability in RE₂Fe₁₄C system has been thoroughly investigated using first-principles calculations in this work. It reveals that the trigonal prisms formed by Fe and C atoms play a crucial role in phase stability. The Fe atoms in these prisms also make the largest contribution to the increase of magnetic moment when substituting B for C, which is induced by the decreasing covalent bonding strength of B–Fe compared to that of C–Fe. B substitution also results in a decrease in magnetic anisotropy. However, a balance between magnetization and coercivity can be achieved through composition optimization. This work provides key insight into the phase stability of the RE₂Fe₁₄C system and is also an important reference for the development of heavy-rare-earth-free high coercivity magnets.