Valence state in R4As3R4As3 (R=YbR=Yb and Eu) studied by resonant and non-resonant X-ray scattering

The resonant and non-resonant X-ray scattering technique have been applied to the observation of a valence fluctuated (VF) state in R4As3R4As3 (R=YbR=Yb and Eu). In Yb4As3Yb4As3, the resonant signal reflecting a short range order of the charge ordering of Yb ions was clearly found at Yb L3L3-edge in the VF state above the charge ordering temperature. This is the first observation of the spatial correlation of the valences in the VF state. The valence state in Eu4As3Eu4As3 was also investigated near Eu L3L3-edge for comparison.