Theoretical investigation on the EPR parameters for VO 2+ doped ZnO–CdS nanocomposites

The three optical absorption bands and electron paramagnetic resonance (EPR) parameters g factors ( g || , g ⊥ ) and the hyperfine structure constants ( A || , A ⊥ ) for VO 2+ doped in the ZnO–CdS nanocomposites are theoretically investigated by using the perturbation formulas of these EPR parameters for a 3 d 1 ion under tetragonally compressed octahedral based on the cluster approach. In the calculation formulas, the relationships between local structure of the VO 2+ dopants and the EPR parameters are established from the crystal-field parameters via the tetragonal distortion (characterized by relative tetragonal compression ratio τ ), and the contributions to EPR parameters arising from the ligand orbital and spin-orbit coupling interactions via covalence effect are considered. Based on the studies, the V 4+ dopants are found to show a relative compression ratio τ (≈ 2.1%) along the z -axis due to Jahn–Teller effect. Calculated results show reasonable agreement with the experimental data. Reasonableness of the proposed model is discussed. Graphical abstract