Theoretical studies on the local structure and spin Hamiltonian parameters for Cu 2+ ions in LiTaO 3 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 Cu 2+ doped in the LiTaO 3 crystal are theoretically investigated by the perturbation formulas for a 3d 9 ion under rhombically elongated octahedral based on the cluster approach. The impurity Cu 2+ was assumed to occupy the host trigonally-distorted octahedral Li + site and experience the Jahn-Teller (JT) distortion from the host trigonal octahedral [TaO 6 ] 10- to the impurity rhombically elongated octahedral [CuO 6 ] 10- . Based on the calculations, the impurity-ligand bond lengths parallel and perpendicular to the C 2 -axis are found to be R || (≈ 2.305 Å) and R ⊥ (≈ 2.112 Å) for the studied [CuO 6 ] 10- cluster, with the planar bond angle θ (≈ 78.2°). Meanwhile, the ground-state wave function for Cu 2+ center in LiTaO 3 was also obtained. The calculated SHPs based on the above local lattice distortions agree well with the experimental data, and the results are discussed.