We investigate the temperature induced mixed valence transition in EuNi2(Si0.2Ge0.8)2 using Eu 3d-4f X-ray absorption spectroscopy (XAS). The unoccupied 4f states are studied as a function of temperature (27-120 K), across the critical valence temperature, Tv = 80 K. The Eu 3d-4f X-ray absorption spectra show systematic changes of the mixed valency with temperature. The Eu2 + and Eu3 + spectral features match very well with atomic multiplet calculations. The observed non-integral mean valence changes systematically from ∼ 2.70 ± 0.03 (27 K) to ∼ 2.35 ± 0.03 (120 K), consistent with bulk-sensitive measurements.
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