INVESTIGATION OF THE SPIN-GLASS SR2FENBO6 BY EXTENDED X-RAY-ABSORPTION FINE-STRUCTURE AND MOSSBAUER-SPECTROSCOPY

Extended X-ray absorption fine structure (EXAFS) and Fe-57 Mossbauer spectroscopy have been used to investigate the cation distributions in the spin-glass Sr2FeNbO6, and the antiferromagnets SrLaFeSnO6 and SrLaFeTiO6. Evidence is presented to suggest that the distribution of cations on the octahedrally coordinated sites is random in all three compounds and that the differences in magnetic behaviour are due to subtle changes in the superexchange. The near-neighbour superexchange alone in a perovskite cannot lead to the frustration associated with a spin-glass. Therefore one is obliged to consider the role of the next-nearest neighbours as the source of frustration. An examination of the available data suggests that the A-site cation may have some role to play in determining the magnetic behaviour.