EPR and Optical Absorption Studies of Cu²⁺ in Boro-Arsenate Glasses

Electron paramagnetic resonance (EPR) and optical absorption studies of xMgO- (25-x) Li₂O-50B₂O₃-25As₂O₃ glasses were made by introducing Cu²⁺ as a spin probe. The EPR spectra of all the glass samples recorded at X-band frequencies have similar spectral features. The Cu²⁺ ions are in well-defined axial sites, but subjected to small distortion leading to the broadening of the spectra. The spin-Hamiltonian parameter values indicate that the ground state of Cu²⁺ is d_{x2- y2} and the site symmetry around Cu²⁺ ions is tetragonal distorted octahedral. The optical absorption spectra exhibited a broadband corresponding to the d-d transition bands of Cu²⁺ ion. By correlating EPR and optical data, the bond parameters were evaluated and the values show purely ionic nature for the in-plane σ bonding and in-plane π bonding. The out-of-plane π bonding is moderately covalent.

Keywords:
Glass; spin-Hamiltonian; Optical Absorption; Electron Spin Resonance