Iron atomic packing in Fe-Ru superlattices by x-ray-absorption spectroscopy

Unusual iron packing in ${\mathrm{Fe}}_{\mathit{x}}$ ${\mathrm{Ru}}_{\mathit{y}}$ superlattices with x varying from 4 to 14 Å and y from 4 to 78 Å was observed by extended x-ray-absorption fine structure and x-ray-absorption near-edge-structure (XANES) analysis. The XANES profile and the first peak of the Fourier transform of the spectrum show a large anisotropy when the polarization of the x-ray synchrotron-emitted beam is in the basal plane of the superlattices or perpendicular to it. The local nature of this result suggests refinement of the structure already deduced by reflection high-energy electron diffraction and x-ray diffraction. The hexagonal packing of iron herein proposed agrees with the structural data found in the literature.