57Fe Moessbauer effect studies of the point defects structure in fast neutron irradiated garnet ferrites Y3Fe5-xAlxO12

Garnet ferrites Y3Fe5-xAlxO12 (x = 0, 0.35, 0.70, 1.00, 1.17) - YAG, stored under room temperature for three years since they were exposed to fast neutrons, have been investigated by means of the nuclear gamma resonance (NGR) method. Thus the effect of 'long-lived' radiational defects upon properties of YAG have been studied. The samples were exposed to a fast neutron flux with an intensity of (0.8-1.5) x 1013 cm-2s-1, and the irradiation doses amounted to 4 x 1018 and 2.6 x 1019 cm-2, besides a Y3Fe5O12 sample was irradiated also with a dose of 7.8 x 1019 cm-2. The NGR measurements have been performed in the transmission geometry, employing a Moessbauer 57Co(Cr) source. (Auth.)