Electronic Structure of the Valence Transition System Eu(Rh_1−xT_x)₂Si₂ (T = Co, Ir) Studied by High-Energy Resolution Fluorescence Detection X-Ray Absorption Spectroscopy

Abstract

The electronic structure of Eu(Rh 1-x T x) 2 Si 2 (T = Co, Ir) showing a valence change with temperature has been investigated by means of high-energy resolution fluorescence detection X-ray absorption spectroscopy (HERFD-XAS). The Eu L 3-edge HERFD-XAS spectra for Eu(Rh 1-x T x) 2 Si 2 distinctly demonstrate that, due to the improvement of the energy resolution, the intensities of Eu 2+ and Eu 3+ components are dependent on temperature. Each component has additional fine structures, which clearly change above and below the transition temperature. These spectral changes are similar to those for EuNi 2 (Si 1-x Ge x) 2 , but the degree of temperature dependence on energy difference between Eu 2+ and Eu 3+ components is different from EuNi 2 (Si 1-x Ge x) 2. The results of this study suggest that a treatment of the many-body interaction is essential to understanding the valence transition of Eu compounds.