Recoilless nuclear-resonance absorption was measured on Y 3GatFe5-tO12 powders with 1.75≤t≤4.0. A constant acceleration spectrometer was used, and the investigations were performed at room temperature, that is above the Curie temperature of these compounds. For each material we observed three resonant absorption maxima with different heights. The position of the maxima on the velocity scale is independent of composition. For each spectrum two doublets which arise from the quadrupole splitting of the 57Fe nuclei are assigned; one doublet arises from the 57Fe nuclei in the tetrahedral (d) sites, whereas the other arises from the 57Fe nuclei in the octahedral (a). From the relative values for the intensities D and A for the d and a sites together with the known amount of t, the fraction x/t of the Ga 3+ ions in the d-sites was determined for each compound x/t=[D(t-2)+3A]/(A+D)t. The results were compared with work on cation distribution in substituted garnets, obtained from (a) magnetization measurements,1,2 (b) x-ray and neutron diffraction,3 and (c) thermodynamics of solid solutions.4 At Ga concentrations t>1.75, our results deviate from the ones obtained from magnetization data. The distribution function proposed in Ref. 4 is consistent with our experimental data over the total range of t. A more complete account of this work is intended for publication elsewhere. © 1969 The American Institute of Physics.
