Creation and thermal annealing of structural defects in neutron-irradiated MgAl2O4 single crystals

Several novel hole-type defects (a hole localized at a regular oxygen ion near a negatively charged structural defect) have been revealed in fast neutron irradiated MgAl₂O₄ crystals using the EPR method. The pulse annealing of the EPR signal of these centers was compared to that of radiation induced optical absorption in the same crystals. Taking into account the determined models of V₁, V₂ and V₂₂ paramagnetic centers, the tentative scenario of the thermal annealing process of neutron-induced defects (hole-type and complementary electron F-type ones) is proposed. In addition, one more paramagnetic hole center consisting of an Al|_Mg as-grown antisite defect near an aluminum vacancy is created just by X-ray irradiation at room temperature.