Nitrogen as the best interstitial dopant among $X$=B, C, N, O and F for strong permanent magnet NdFe$_{11}$Ti$X$: First-principles study

摘要

We study magnetic properties of NdFe$_{11}$Ti$X$, where $X$=B, C, N, O, andF, by using the first-principles calculation based on the density functionaltheory. Its parent compound NdFe$_{11}$Ti has the ThMn$_{12}$ structure, whichhas the symmetry of space group $I4/mmm$, No. 139. The magnetization increasesby doping B, C, N, O, and F at the $2b$ site of the ThMn$_{12}$ structure. Theamount of the increase is larger for $X$=N, O, F than for $X$=B, C. On theother hand, the crystal field parameter $\langle r^{2} \rangle A_{0}^{2}$,which controls the axial magnetic anisotropy of the Nd $4f$ magnetic moment,depends differently on the dopant. With increase of the atomic number from$X$=B, $\langle r^{2} \rangle A_{0}^{2}$ increases, takes a maximum value for$X$=N, and then turns to decrease. This suggests that in NdFe$_{11}$Ti$X$,nitrogen is the most appropriate dopant among B, C, N, O, and F for permanentmagnets in terms of magnetization and anisotropy. The above calculatedproperties are explained based on the detailed analysis of the electronicstructures of NdFe$_{11}$Ti$X$.