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

Resumo

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.