Investigation of the Fe K-edge XANES Spectra from Fe1-xGaxSbO4: Local versus Nonlocal Excitations

The Fe K-edge X-ray absorption near-edge (XANES) spectra from Fe1-xGaxSbO4, having a rutile-like structure, have been investigated. Similar to the Ti K-edge XANES spectrum from TiO2 (rutile), the low-energy pre-edge region observed in the Fe K-edge spectra is too broad to be representative of only a local, quadrupolar 1s --> 3d excitation. The broadness of this peak results from the presence of a nonlocal transition, referred to as an intersite hybrid, which involves the excitation of Is electrons to unoccupied 3d states of a next-nearest-neighbor Fe atom. (These 3d states overlap Fe 4p states of the absorbing atom through O 2p states.) With increasing Ga concentration, the intensity of the intersite hybrid peak decreases because of a deficiency of unoccupied next-nearest-neighbor 3d states. This observation provides important information on how the peak intensities of these nonlocal excitations are affected by substitution of the constituent elements.