Magnetic and optical properties and electron paramagnetic resonance of gadolinium-containing oxide glasses

Magnetic susceptibility, electron paramagnetic resonance (EPR) and optical absorption have been studied in a glass system 20La₂O₃-22Al₂O₃-23B₂ O₃-35 (SiO₂ + GeO₂) with a part of La₂O₃ substituted by Gd₂O₃ in different concentrations. Positive Weiss constants have been found in more heavily doped glasses and ascribed to clustering of Gd³⁺ ions. Computer simulations of the EPR spectra show that the short-range ordering in the environment of the Gd³⁺ ions is well preserved. The relative distribution widths of the ligand coordinates are less than 2%. In the more heavily doped glasses the EPR spectra are superpositions of signals arising from isolated ions and ferromagnetic clusters. The increase of Gd³⁺ concentration is shown to change substantially the strong optical absorption edge while only small changes of f-f absorption band characteristics are observed. This difference is associated with the different effect of the Gd ion clustering on the mechanisms of the strong absorption in the ultraviolet region and the f-f absorption.