Theoretical studies on the local structure and spin Hamiltonian parameters for Cu²⁺ ions in LiTaO₃ crystal

The local structure and spin Hamiltonian parameters (SHPs) g factors (g(x), g(y), g(z)) and the hyperfine structure constants (A(x), A(y), A(z)) for Cu2+ doped in the LiTaO3 crystal are theoretically investigated by the perturbation formulas for a 3d(9) ion under rhombically elongated octahedral based on the cluster approach. The impurity Cu2+ was assumed to occupy the host trigonally-distorted octahedral Li+ site and experience the Jahn-Teller (JT) distortion from the host trigonal octahedral [TaO6](10-) to the impurity rhombically elongated octahedral [CuO6](10-). Based on the calculations, the impurity-ligand bond lengths parallel and perpendicular to the C-2-axis are found to be R-||(approximate to 2.305 & Aring;) and R-perpendicular to (approximate to 2.112 & Aring;) for the studied [CuO6](10-) cluster, with the planar bond angle theta (approximate to 78.2 degrees). Meanwhile, the ground-state wave function for Cu2+ center in LiTaO3 was also obtained. The calculated SHPs based on the above local lattice distortions agree well with the experimental data, and the results are discussed.