Luminescence and EPR spectroscopy of neutron-irradiated single crystals of magnesium aluminium spinel

• Photo-, cathodo- and thermally stimulated luminescence; conventional and pulse EPR.
• In irradiated spinel Mn2+ ions are moved from tetrahedral to octahedral interstices.
• An electron from an F+ centre is in superhyperfine interaction with 27Al nuclei.

Neutron irradiated single crystals of stoichiometric MgAl2O4 and MgAl2O4:Mn2+ (0.15 wt. %) were studied using the methods of luminescence spectroscopy and versions of electron paramagnetic resonance. In stoichiometric MgAl2O4:Mn2+ single crystals, the transition of a part of manganese impurity ions from tetrahedral to octahedral coordination, caused by irradiation with fast fission neutrons, is detected using photoluminescence spectra. This fact confirms the partial inversion of a normal spinel due to neutron-irradiation. Using pulse EPR technique it is shown that an electron in the field of oxygen vacancy (i.e. from neutron-irradiation induced F+ centres, which are spatially separated from each other) is in hyperfine interaction only with neighbouring 27Al nuclei with nuclear spin 5/2.