Theoretical calculation on the magnetocrystalline anisotropy of NdFe_10.5V_1.5N_x

The NdFe_10.5V_1.5N_x compounds with different nitrogen content have been synthesized. The dependence of magnetic properties at room temperature on the nitrogen content was investigated in order to give evidence of the importance of the nitrogen content on the magnetic anisotropy of the rare earth sublattice. In the meantime, the theoretical calculations were performed to analyze the nitrogen content dependence of the magnetocrystalline anisotropy constants K_1,2, as well as the anisotropy field H_a in the NdFe_10.5V_1.5N_x. The results confirmed that the second-order crystal-field parameter A₂₀ is dominant and, in the nitrides, the chief contribution to A₂₀ comes from nitrogen located at 2b sites. Finally, the increase of nitrogen content will first turn the easy-plane magnetocrystalline anisotropy of the rare earth sublattice into easy-axis one and then enhance it linearly to a much larger value, which is in quite good agreement with experiment.