A study of the impurity structure for 3d3 (Cr3+ and Mn4+) ions doped into rutile TiO2 crystal

The local environment around 3d3 (Cr3+ and Mn4+) ions doped into rutile TiO2 crystals has been investigated using superposition model (SPM) analysis. The zero-field splitting (ZFS) parameters (ZFSPs) D and E are modeled for the Cr3+ and Mn4+ ions at both the substitutional Ti sites with local symmetry orthorhombic D2h and the interstitial sites (ISs) with the same symmetry. Several model parameter sets are adopted so as to acquire the best agreement between the calculated ZFSPs and those measured by electron magnetic resonance (EMR). The feasible values of the structural distortions (ΔRY, ΔRXZ and Δθ) resulting from dopant Cr3+ and Mn4+ ions are determined. As a result, it is confirmed that Mn4+ ions substitute for Ti4+ sites in rutile TiO2 crystal; however, it is suggested that Cr3+ ions may replace at not only Ti4+ site but also IS.

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► Modeling of the ZFSPs of the Cr3+ and Mn4+ centers for rutile TiO2 was carried out.
► Both the substitutional Ti4+ ion sites and interstitial sites (ISs) were considered.
► We confirmed that Mn4+ ions substitute for Ti4+ sites in rutile TiO2 crystal.
► It is suggested that Cr3+ ions may replace at not only Ti4+ site but also IS.