EPR of neutron-radiation-induced defects in Gd₃Ga₅O₁₂

Stable radiation-induced defects can have significant effects on materials usability in solid state lasers, scintillators, and other devices that may be exposed to ionising radiation. This study investigates several paramagnetic centres in gadolinium gallium garnet (Gd₃Ga₅O₁₂). Analysis of single-crystal electron paramagnetic resonance (EPR) spectra was performed after irradiation with fast neutron radiation. It was determined that paramagnetic centres with highly anisotropic g-factor values are formed and remain stable well above room temperature. The irregular defect symmetry suggests that one of the defects is formed along the direction of cubic lattice diagonal. This defect was attributed to Ge centres resulting from Ga neutron capture coupled with multiple oxygen vacancies. The origin of other paramagnetic centres is discussed based on unusual temperature dependencies of EPR spectra and ab initio calculations.