Electron paramagnetic resonance of Cr3+ in near-stoichiometric LiTaO3

Electron-paramagnetic-resonance (EPR) experiments on the dominant Cr3+ center in near-stoichiometric LiTaO3 crystals, grown by the double crucible Czochralski method, are reported. A near complete roadmap of EPR positions was obtained allowing an accurate determination of the spin-Hamiltonian parameters. Newman superposition model calculations of zero-field splitting term were performed and support the model of Cr3+ incorporation within the Li octahedron. Calculations were also made for Cr3+ in LiNbO3, again good agreement with a Li site model was obtained for the main EPR center. The temperature dependence of the zero-field splitting parameter for Cr3+ in LiTaO3 was found to show anomalous behavior in the region of 40 K, suggesting the presence local structural instability at the ion site.