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

Abstract Boro-bismuth glasses containing BaO-TeO 2 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 2 B 1g  → 2 B 2g  and 2 B 1g  → 2 E 2g respectively. A large anisotropy (Δ g  =  g ∥  −  g ⊥ ) due to the distortion around the Cu 2+ site by the ligands was observed. Experimental and theoretical EPR results have shown that g ∥  >  g ⊥  >  A ⊥ g e (=2.0023) and A ∥  > A ⊥ . The ligand field around Cu 2+ ions is tetragonally elongated octahedral with d x 2 − y 2 ( 2 B 1g ) 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 τ σ determine the bonding parameters α 2 , β 2 , β 1 2 and τ π Theoretical investigations were performed using the high order perturbation formulae for 3d 9 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 Cu 2+ -O 2− octahedron experiences 0.50% elongation along C 4 axis. The theoretical and experimental results are well in coincidence within the error limits.