Electrical and magnetic properties of copper tellurite glasses

The glasses of composition (100 − x)TeO2–xCuO (x = 10, 20, 30, 40, 50 mol%) were prepared by melt quenching method. Differential Scanning Calorimetry (DSC), DC conductivity, Electron Spin Resonance (ESR), and magnetization measurements were undertaken on the glass samples. The glass-transition temperature, T g, decreases and the thermal stability (ΔT = T o − T g) increases with the increase in CuO content. The electrical conduction in these glasses is due to polaron hopping mechanism in the adiabatic regime. The ESR spectra of the x = 10 glass consists of a broad symmetrical line characteristic of Cu2+ clusters. The ESR signal linewidth increases and intensity decreases drastically with increase in CuO content from 10 to 20 mol%. No ESR signal could be observed for the glass samples with x ≥ 40. The absence of EPR signal is ascribed to antiferromagnetic interactions between the Cu2+ clusters. The magnetization measurements indicate all the samples to be in paramagnetic state. The M–H plots show a small hysteresis loop in the low-field region. These studies indicate the coexistence of antiferromagnetic (AFM) as well as ferromagnetic (FM) interactions between Cu 2+ ions in these glasses. The significant change in the properties of the glass at x = 20 is ascribed to the structural changes caused by CuO in the glass matrix.