Valence-Selective Local Atomic Structures on an YbInCu₄ Valence Transition Material by X-Ray Fluorescence Holography

Abstract

An experimental technique of x-ray fluorescence holography for investigating valence-selective local structures was established by employing a characteristic incident x-ray energy near an absorption edge, and it was adopted to discriminate environments around Yb2+ and Yb3+ ions in an YbInCu4 valence transition material below and above the transition temperature of 42 K. The reconstructed images of the neighboring atoms around Yb3+ show a fcc structure as observed by diffraction experiments, whereas those around Yb2+ have curious cross (+) features, indicating a positional shift of the centered Yb2+ ions from the fcc lattice point, due to a much larger radius of the Yb2+ ions.