Abstract
Several hole-type paramagnetic defects (a hole localized at a regular oxygen ion near charged structural defect/defects) have been revealed in fast-neutron-irradiated MgO⋅2.5Al2O3 single crystals using the EPR method. Three of them (a dominant V1 and small amount of V2 and V22) were recently revealed in a neutron-irradiated stoichiometric MgAl2O4, while a novel V4 center, ascribed to a hole in a form of O− ion nearby a complex of a magnesium vacancy and a positively charged antisite defect (V4 ≡ O–‑VMg‑Al|Mg), was created by fast neutrons only in a nonstoichiometric single crystal. The pulse annealing of the EPR signal of these centers was compared to that of radiation induced optical absorption in the same crystals. The EPR and optical characteristics of the holes localized near as-grown structural defects in X-ray irradiated 1:1 and 1:2.5 Mg‑Al spinel crystals were compared as well. The tentative scenario of the thermal annealing process of neutron-induced defects (hole-type and complementary electron F-type ones) in MgO⋅2.5Al2O3 was considered.
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