Investigation on the Spin Hamiltonian Parameters and the Local Structures for Cu<sup>2+</sup> Centers in Sodium Phosphate and Heavy Metal Fluoride Glasses

The spin Hamiltonian parameters (the anisotropic g factors g_||, g_⊥ and hyperfine structure constants A_||, A_⊥) for the Cu²⁺ sites in sodium phosphate glasses Na₂O–9P₂O₅ and heavy metal fluoride glasses 60ZrF₄–5LaF₃–20BaF₂–15NaF are theoretically investigated by using the high (fourth-) order perturbation formulas of these parameters for a 3d⁹ ion in tetragonally elongated octahedra. In these formulas, the contributions to the g factors from the tetragonal distortion, characterized by the tetragonal field parameters Ds and Dt, are taken into account by considering the relative axial elongation of the ligand octahedron around the Cu²⁺ due to the Jahn–Teller effect. According to the calculations, the ligand octahedra around Cu²⁺ are suggested to suffer about 12% and 18% relative elongation along the C₄-axis for the studied Na₂O–9P₂O₅ and 60ZrF₄–5LaF₃–20BaF₂–15NaF glasses, respectively. The local structures characterized by the above axial elongations are discussed.