Theoretical Calculation of the Crystal Field Parameters of GdCo₅, GdFe₁₂, GdFe₁₂N, Gd₂Fe₁₇, and Gd₂Fe₁₇N₃ Compounds

Abstract

The electronic structures of GdCo₅, GdFe₁₂, GdFe₁₂N, Gd₂Fe₁₇, and Gd₂Fe₁₇N₃ have been calculated self-consistently by full-potential linearized augmented plane wave method within the framework of the local spin density approximation. The second order crystal field parameters (A₂⁰) at Gd-site of these compounds have been determined carefully from the calculated charge distribution. For GdCo₅, although the calculated value of A₂⁰ is larger than experimental ones for SmCo₅, it is found that the crystal structure is very suitable for producing the large negative value of A₂⁰. For the other compounds, the calculated values of A₂⁰ except for GdFe₁₂ are also larger than experimental ones. The trend of the increase of A₂⁰ by introducing nitrogen is, however, in agreement with experimental results. In RFe₁₁Ti and R₂Fe₁₇ (R=rare earth), the increase of the magnetocrystalline anisotropy energy by introducing nitrogen can be understood from the increase of the asphericity of charge distribution around R ion due to the bonding state between R ion and nitrogen.