Temperature-induced valence transition in EuNi2(Si1–xGex)2 investigated by high-energy resolution fluorescence detection X-ray absorption spectroscopy

Electronic structures of the temperature-induced valence transition system EuNi2(Si1–xGex)2 with x = 0.70, 0.79, 0.82 have been investigated by means of high-energy resolution fluorescence detection X-ray absorption spectroscopy (HERFD-XAS). The HERFD-XAS spectra clearly change their intensities of Eu2+ and Eu3+ components which directly reflect the temperature-induced valence transition. For x = 0.70, gradual spectral change exhibits a continuous valence transition, while drastic changes for x = 0.79 and 0.82 indicate first-order valence transitions. High-energy resolution measurements made it possible to observe additional fine structures which are recognized more clearly below the transition temperature. Existence of these fine structures suggests that many-body effect plays an important role in the temperature-induced valence transition of this system. The variation of Eu mean valence estimated from the HERFD-XAS spectra for each x correlates with that of magnetic susceptibility. •Valence transition of EuNi2(Si1-xGex)2 proved by means of Eu L3 HERFD-XAS.•Temperature-dependent fine structures reminiscent of change in many-body interaction through the valence transition.•Variation of Eu valence through the valence transition is associated with that of magnetic states.