Effects of Gd3+ : Ag co-doping on structural and magnetic properties of lead tellurite glass ceramics

Lead tellurite glass ceramics doped with variable amounts of Gd3+ ions and co-doped with fixed amounts of silver (Ag2O or Ag metallic nanoparticles, AgNPs) have been prepared and investigated by X-ray diffraction (XRD), density, electron paramagnetic resonance (EPR) and magnetic susceptibility measurements. The EPR spectra of the studied samples exhibit the typical "U"-type shape with effective g-values of approximate to 6, 2.8, 2.0 and a weaker feature at g approximate to 4.8. At higher contents of Gd3+ ions the spectral features are broadened and finally are dominated by a broad absorption line located at g approximate to 2.0 and a weaker feature at g approximate to 6. The broad EPR line centered at g approximate to 2.0 is associated to the Gd3+ ions present predominantly as clustered species. The paramagnetic susceptibility (chi) was measured at various temperatures and from the 1/chi versus T dependence the molar Curie constant (Cm) and the paramagnetic Curie temperature (theta(P)) have been evaluated. Magnetic susceptibility data show that for low Gd2O3 contents, x <= 3 mol%, the Gd3+ ions are randomly distributed in the host glass ceramics matrix and are present only as isolated species. For higher Gd2O3 contents, x > 3 mol%, the Gd3+ ions appear as both isolated and antiferromagnetically coupled species. (C) 2015 Elsevier Ltd and Techna Group S.r.l. All rights reserved.