Investigations on the Local Structures and the Spin Hamiltonian Parameters for Cu2+ in (90–x)TeO2–10GeO2–xWO3 Glasses

Abstract

Abstract The local structures and the spin Hamiltonian parameters (SHPs) for Cu2+ in (90–x)TeO2–10GeO2–xWO3 glasses are theoretically investigated at various WO3 concentrations (x=7.5, 15, 22.5 and 30 mol%). Subject to the Jahn-Teller effect, the [CuO6]10− groups are found to experience the small or moderate tetragonal elongation distortions (characterised by the relative tetragonal elongation ratios ρ≈0.35–3.09%) in C4 axis. With only three adjusted coefficients a, b and ω, the relevant model parameters (Dq, k and ρ) are described by the Fourier type and linear functions, respectively, and the measured concentration dependences of the d–d transition bands and SHPs are reproduced. The maximum of g ∥ and the minimum of |A ∥| at x=15 mol% are illustrated from the abrupt decrease of the copper–oxygen electron cloud admixtures or covalency and the obvious decline of the copper 3d–3s (4s) orbital admixtures due to the decreasing electron cloud density around oxygen ligands spontaneously bonding with Cu2+ and Te4+ (W6+), respectively.