The Influence of Hydrostatic Pressure on Intermediate Europium Valence State in Compound EuCu2Ge2

We report the high-pressure XANES study of europium intermediate valence in the rare-earth compound EuСu2Ge2. The hydrostatic pressure-dependence of europium valence was obtained in a wide pressure range (1-30 GPa) at room temperature. The saturation region of the europium valence was found at the pressure higher than 20 GPa, when the valence reaches the value of 2.89. The study compared the mechanisms of external and “chemical” pressure by the Si substitution in Ge site in series EuCu2(SixGe1-x)2. The experimental results were supported by band structure calculations in the framework of DFT, which allowed us to discuss the features of 3d-4f hybridization model for this system.