Experimental and theoretical electron paramagnetic resonance and optical studies of Cu2+ spin probe in BaO-TeO2-Bi2O3-B2O3 glass system

Boro-bismuth glasses containing BaO-TeO2 in varying proportions were prepared by the conventional melt quenching method. One mol% of CuO was integrated as the spin probe to the glass systems. The prepared glasses were transparent, bubble-free and light blue in color. The optical absorption spectra revealed two absorption bands corresponding to the transitions 2B1g →2B2g and 2B1g →2E2g respectively. A large anisotropy (Δg = g∥ − g⊥) due to the distortion around the Cu2+ site by the ligands was observed. Experimental and theoretical EPR results have shown that g∥ > g⊥ > A⊥ge (=2.0023) and A∥ >A⊥. The ligand field around Cu2+ ions is tetragonally elongated octahedral withdx2−y2 (2B1g) ground state. The decreased peak-to-peak linewidth (ΔB) with increasing BaO content is attributed to decrease in dipolar interaction between the copper ions. The number of EPR active copper ions (N) and the paramagnetic susceptibility (χ) were computed. EPR and optical data were used to τσ determine the bonding parameters α2, β2, β12 and τπ Theoretical investigations were performed using the high order perturbation formulae for 3d9 ions in tetragonally elongated octahedra to determine the spin-Hamiltonian parameters (SHP) and d-d transition bands. The variation of BaO content in the glass matrix had affected the orbital reduction factor, spin-orbit coupling coefficient, cubic and tetragonal field parameters. The Cu2+-O2− octahedron experiences 0.50% elongation along C4 axis. The theoretical and experimental results are well in coincidence within the error limits.