Investigation on the EPR parameters and local structure for the Cu2+ center in ZnAl2O4 spinel

• Tetragonal field parameters are associated with the local structures around Cu2+.
• EPR parameters and local structures are analyzed for ZnAl2O4:Cu2+.
• In the calculation, ligand contributions are included from the cluster approach.

High-order perturbation formulas for a 3d9 ion in tetragonally elongated octahedral was applied to calculate the electron paramagnetic resonance (EPR) parameters (g factors g||, g⊥ and hyperfine structure constants A||, A⊥) of the tetragonal Cu2+ center in ZnAl2O4 spinel at the temperature T=4.2 K. In the calculations, the required crystal-field parameters are estimated from the superposition model which enables correlation of the crystal-field parameters and hence the EPR parameters with the tetragonal distortion (characterized by relative tetragonal elongation ratio ρ along the C4 axis due to the Jahn–Teller effect) of [CuO6]10− cluster, and the ligand orbital and spin–orbit coupling contributions are included on the basis of the cluster approach in view of moderate covalency for the studied systems. The calculated results show good agreement with the experimental data.