X-RAY STANDING-WAVE ANALYSIS OF THE BI PREFERENTIAL DISTRIBUTION IN Y3-XBIXFE5O12 THIN-FILMS

The X-ray standing-wave method was used to study the distribution of bismuth ions on the dodecahedral sublattice of a thin yttrium-bismuth iron garnet film. The film was grown epitaxially on a (001)-oriented substrate of gadolinium gallium garnet. Measurement of the fluorescence of Bi3+, Y3+, Fe3+ and Gd3+ ions was made under conditions such that an X-ray standing wave was formed during diffraction from the layer studied. We have shown experimentally that the dodecahedral sites c(z), and c(xy) are not equivalent - the fraction of Bi3+ ions in c(z) positions is 0.44 +/- 0.02 and in c(xy), positions 0.56 +/- 0.02, while in the case of crystallographically equivalent sites (or, for a uniform distribution of Bi3+ ions over dodecahedral sites) these fractions are 1/3 and 2/3, respectively,