EPR and magnetic characterization of Fe2O3-TeO2 and CuO-TeO2 glasses obtained by melt quenching and sol-gel processes

Samples of the xFe(2)O(3) center dot (1-x)TeO2 and xCuO center dot (1-x)TeO2 glass systems with x <= 0.50 were prepared by melt quenching and sol-gel processes and were investigated by electron paramagnetic rezonance (EPR) spectroscopy and magnetic susceptibility measurements. EPR data show the presence of Fe3+ and Cu2+ ions in the host glass matrices. Analysis of compositional evolution of EPR spectra reveals the distribution of Fe3+ and Cu2+ ions in the tellurate glass and offers information on their interactions and microvicinities. Magnetic susceptibility and EPR data prove that iron and cooper ions are present in the host tellurate glass as isolated species and species coupled by dipolar and exchange interactions of antiferromagnetic nature. These data show an important clustering tendency of iron and cooper ions in the studied tellurate glasses. As proved by EPR and magnetic susceptibility data, besides the Fe3+ and Cu2+ ions, Fe2+ and Cu+ species are also present in the studied tellurate glasses. The Fe3+ -> Fe2+ and Cu2+ -> Cu+ reduction processes occur in these samples with different intensities as function of the preparation technique and samples composition influencing their magnetic behavior. (C) 2015 Elsevier B.V. All rights reserved.