Studies on the g-factors of the copper(II)–oxygen compounds

The g factors for Cu2+ in meta-zeunerite (Cu(UO2)2(AsO4)2·3H2O), kroehnkite (Na2Cu(SO4)2·2H2O), copper benzoate (Cu(PhCO2)2·3H2O) and diaboleite (Pb2Cu(OH)4Cl2) of the tetragonal phase are uniformly treated by high order perturbation formulas for 3d9 ions in tetragonally elongated octahedra. The calculation results are in good agreement with the observed values and systematically analyzed in view of the local structures around Cu2+. The g anisotropies Δg (= g‖−g⊥) are largely ascribed to the local tetragonal elongations of the Cu2+ sites, characterized by the relative elongation ratios (R‖−R⊥)/R̅ ≈ 19%, 21%, 27% and 30% for metazeunertie, kroehnkite, copper benzoate and diaboletie, respectively. The anomalous valley (minimum) of relative g anisotropy for copper benzoate is attributed to the modification of the Cu2+ electronic states due to the phenyl ring. The ligand orbital contributions are found to be significant due to covalency, and should be taken into account. The present study would be helpful to the unified investigations of structures and properties of the copper oxygen compounds.