LAUSR

Enhancing energy product and thermal stability at the same time while retaining the concentration of rare-earth (RE) elements in RE-$3d$ compounds is desirable for permanent magnetic applications. Herein, all-electron electronic structure calculations are used to reveal possibilities of enhancing saturation magnetization (${\ensuremath{\mu}}_{0}{M}_{s}$) and uniaxial magnetic anisotropy (${K}_{u}$) in ${\mathrm{Th}\mathrm{Mn}}_{12}$-type ${\mathrm{Sm}\mathrm{Fe}}_{12}$ by carefully exploring substitutional and interstitial impurities. More specifically, an addition of only one N atom, among $2p$-electron elements, per formula unit cell of ${\mathrm{Sm}\mathrm{Fe}}_{12}$ not only improves its structural stability but also enhances ${K}_{u}$ by more than 2 times and ${\ensuremath{\mu}}_{0}{M}_{s}$ up to 5%, which are superior to those of the currently known permanent magnetic materials. Our calculations further demonstrate that these permanent magnetic properties of ${\mathrm{Sm}\mathrm{Fe}}_{12}$ can also be enhanced by replacing $\mathrm{Fe}$ with $\mathrm{Co}$, in agreement with an experiment [Y. Hirayama et al., Scr. Mater. 138, 62 (2017)].