Investigation of the local structure of Cu²⁺ions doped in alkali lead tetraborate glasses by their electron paramagnetic resonance and optical spectra

Abstract

The local structure of the Cu 2+ centers in alkali lead tetraborate glasses was theoretically studied based on the optical spectra data and high-order perturbation formulas of the spin Hamiltonian parameters (electron paramagnetic resonance g factors g , g ⊥ and hyperfine structure constants A , A ⊥ ) for a 3d 9 ion in a tetragonally elongated octahedron. In these formulas, the relative axial elongation of the ligand O 2− octahedron around the Cu 2+ due to the Jahn-Teller effect is taken into account by considering the contributions to the g factors from the tetragonal distortion which is characterized by the tetragonal crystal-field parameters Ds and Dt. From the calculations, the ligand O 2− octahedral around Cu 2+ is determined to suffer about 19.2% relative elongation along the C 4 axis of the alkali lead tetraborate glass system, and a negative sign for A and a positive sign for A ⊥ for these Cu 2+ centers are suggested in the discussion.