Investigating the impurity structure for Fe3+ ions doped into rutile titanium dioxide single crystal

The local environment around Fe³⁺ centers in rutile TiO₂ crystals is studied by employing fourth-order perturbation theory formula based on the dominant spin–orbit coupling mechanism. The zero-field splitting parameters (ZFSPs) D and E and crystal field parameters are modeled for the Fe³⁺ ions not only at the substitution Ti⁴⁺ site, but also at the interstitial site with local symmetry D_2h. In order to acquire the best agreement between the calculated ZFSPs and those measured by electron magnetic resonance, the model parameters are adjusted on the basis of several approaches. This enables us to determine the feasible values of the structural distortions resulting from dopant Fe³⁺ ions. Consequently, it is confirmed that Fe³⁺ ions substitute for Ti⁴⁺ sites in rutile TiO₂ crystals.