Studies of the Spin Hamiltonian Parameters for NiX_2 and CdX_2:Ni~(2+) (X = Cl, Br)

摘要

The spin Hamiltonian parameters (zero-field splitting D and the g factors) for NiX_2 and CdX_2:Ni~(2+) (X=Cl, Br) are quantitatively investigated from the perturbation formulas of these parameters for a 3d~8 ion in trigonally distorted octahedra based on the cluster approach. In the calculations, the trigonal field parameters v and v' are determined from the superposition model and the local structures of Ni~(2+) in the halides. The theoretical g factors show reasonable agreement with the observed values, and the experimental D for CdX_2:Ni~(2+) are also interpreted by considering suitable lattice distortions (angular decreases) in the impurity-ligand bond angles related to the C_3 axis due to the size mismatching substitution. The contributions from the ligand orbital and spin-orbit coupling interactions are important and should be taken into account.