EPR g factors and defect structures for Co2+ ions at the substitutional and interstitial sites of SnO2 lattice

The EPR g factors gi ( i = x, y, z) for Co2+ ions at both the substitutional ( i. e. Sn4+) and interstitial sites of SnO2 lattice are calculated from the second-order perturbation formulas based on the cluster approach for g factors of 3d(7) ions in rhombic octahedral clusters. The calculated results for Co2+ at the substitutional site are in line with the experimental values. For Co2+ at the interstitial site, the calculated g(y) and g(z) are close to the observed values, but the calculated g(x) is in disagreement with the observed one. The causes resulting in the disagreement are discussed. The defect structures of both Co2+ centers in SnO2 are also estimated from the calculations.