EPR and optical spectroscopy of neutron-irradiated Gd3Ga5O12 single crystals

Abstract In this paper, we have performed comparative analysis of EPR, optical absorption (OA) and luminescence spectra for a series of Gd3Ga5O12 (GGG) single crystals irradiated with fast neutrons with fluencies varied from 1016 to 1020n/cm2. In a crystal irradiated with the maximum neutron fluence, the EPR spectra demonstrated the formation of several paramagnetic defects. In particular, EPR spectrum shows a strong resonance at (effective) g ≈ 1.4 with practically isotropic behavior in the crystal rotation around the [1 1 1] direction (magnetic field being perpendicular to [1 1 1]) and several weaker lines in the g ≈ 1.1–2.6 region, which show more pronounced angular dependences. While the photoluminescence of non-irradiated GGG is characterized by uncontrolled impurities, in the case of neutron-irradiated GGG, a broad asymmetric luminescence band was observed with a peak at 725–733 nm, which increased with fluence. Consequently, this band can be associated with the formation of radiation defects.