Theoretical study of EPR spectra and local structure for (NiO 6) 10− cluster in LiNbO 3:Ni 2+ and Al 2O 3:Ni 2+ systems

Abstract

For a d 8 configuration ion, the 45×45 complete energy matrix, which contains the electron–electron repulsion interaction, the ligand–field interaction, the spin–orbit coupling interaction as well as the Zeeman interaction, has been established. By diagonalizing the complete energy matrix, the local lattice structure, EPR parameters ( D, g //, g ⊥) and optical absorption spectra for Ni 2+ ions doped in LiNbO 3 and Al 2O 3 have been investigated. The local structure distortion parameters Δ R, Δ θ 1 and Δ θ 2 are determined for LiNbO 3:Ni 2+ and Al 2O 3:Ni 2+ systems, simultaneously. These results show that local structure of (NiO 6) 10− cluster exhibits an elongation distortion in both LiNbO 3:Ni 2+ and Al 2O 3:Ni 2+ systems, in spite of the different reasons of the elongation in both systems. In addition, we have found that the orbit reduction effect is very important to understand the anisotropic g-factors for Ni 2+ ions doped in LiNbO 3 and Al 2O 3 crystals.