Crystal structure and magnetic properties of lithium nitridoferrate: Density functional theory calculations

We report on first-principles calculations to study the effect of the substitution of Li by Fe in Li ₃N. We have investigated the electronic structure and magnetic properties of the iron nitridoferrate compound Li ₂(Li _0.75Fe _0.25)N using the supercell approach. In this work, the strong correlations among Fe-3 d electrons are treated by GGA + U, and the spin–orbit coupling is also taken into account. Ferromagnetic coupling between Fe ions was found for large Fe-Fe distances, which is in excellent agreement with the experimental results. We also showed that this indirect exchange coupling between the localized Fe ions is due to a RKKY-like interaction. The magnetic moment is primarily from Fe atoms. The calculations of the band structure and density of states have confirmed the experimentally observed insulating character with a band gap energy value of 0.44 eV. We also demonstrated that the spin–orbit coupling is responsible for the small value of the orbital moment. The total hyperfine field (B _TOT), the electric field gradient (EFG), and the magnetocrystalline anisotropy energy (Δ) were calculated and compared to the experiment. We hypothesize that the RKKY magnetic interaction, in combination with magnetic anisotropy, likely contributes to the stability of the ferromagnetic state.