材料期刊网

The spin Hamiltonian parameters (the anisotropic g factors, the hyperfine structure constants and the ligand superhyperfine parameters) for the tetragonal Rh(2+) centers in MgO and CaO are theoretically studied from the perturbation formulae of these parameters for a 4d(7) ion in tetragonally elongated octahedra. In these formulae, the related molecular orbital coefficients as well as the ligand unpaired spin densities are determined quantitatively from the cluster approach in a uniform way. The above centers are attributed to Rh(2+) occupying divalent cation sites in MgO (and CaO), associated with a relative elongation of 0.5% ( and 1.4%) along the [001] (or C(4)) axis due to the Jahn-Teller effect. The calculated spin Hamiltonian parameters based on the Jahn-Teller elongations are in good agreement with the observed values. The local structures of the impurity centers are discussed.