Studies on EPR Parameters and Local Structures for the Rhombic Cu2+ Center in the ZnGeO4 · 6H2O Crystal

Abstract

The electron paramagnetic resonance (EPR) parameters (g factors and hyperfine structure constants) and local structures for the impurity Cu²⁺ center in ZnGeO₄ · 6H₂O crystal are theoretically studied using the perturbation formulas of these parameters for a 3d⁹ ion in rhombically elongated octahedra. These formulas are based on a two-spin-orbit-parameter model in which the contributions to the EPR parameters due to both the spin-orbit parameter of the central 3dⁿ ion and that of ligand ion are included. Based on the calculation, the relative axial elongation ratio ρ (≈7.3%) along z-axis and the relative planar bond length variation τ (≈4.3%) along x- and y-axes are found for [Cu(H₂O)₆]²⁺ cluster in ZnGeO₄ · 6H₂O crystal. The above local rhombic distortions of the Jahn–Teller nature around Cu²⁺ can suitably account for the axial and perpendicular anisotropies of the observed EPR parameters.