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 3d⁹ 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 C₂-axis are found to be R_||(≈ 2.305 Å) and R_⊥ (≈ 2.112 Å) for the studied [CuO₆]¹⁰⁻ cluster, with the planar bond angle θ (≈ 78.2°). 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.