Zero-field splitting of 3d⁵(S=5/2) ions in axial symmetry: correlation with the Racah and ligand-field parameters

Abstract

The influence of the ligand-field inter-electronic repulsions and spin-orbit interaction on the zero-field splitting (ZFS) of 3d5 (s=5/2) ions in axial symmetry has been investigated on the basis of a complete calculation. ZFS diagrams valid for both tetragonal and trigonal symmetry and every value of the Racah parameter B are presented. The absolute value of the second-order AFS parameter b20 is found to be strongly dependent on B, C/B, Dq, zeta (3d) and the fourth-order axial parameter of the ligand-field operator. The last cited is the only parameter effective in determining the sign of the ZFS. The inadequacy of the commonly made assumption of a linear or regular dependence of b20 on the axial distortion of the centres is briefly discussed.