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 ≈6, 2.8, 2.0 and a weaker feature at g≈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≈2.0 and a weaker feature at g≈6. The broad EPR line centered at g≈2.0 is associated to the Gd3+ ions present predominantly as clustered species. The paramagnetic susceptibility (χ) was measured at various temperatures and from the 1/χ versus T dependence the molar Curie constant (CM) and the paramagnetic Curie temperature (θp) 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.