Spin-Hamiltonian parameters and defect structure for Co4+ in Al2O3:Mg2+ crystal

The spin-Hamiltonian parameters (g factors gparallel , gperpendicular and hyperfine structure constants Aparallel and Aperpendicular) for Co4+ ion in Al2O3:Mg2+ crystals are calculated from the resonance theory related to the low-spin 2T2 term in trigonal symmetry. The calculated values are in reasonable agreement with the observed values. From the calculation, the defect structure of Co4+ center in Al2O3:Mg2+ crystal is obtained. The result is consistent with the expectations based on the electrostatic interaction and electron cloud overlap. The signs of hyperfine structure constants Aparallel and Aperpendicular are suggested