High-magnetic-field XMCD as a novel tool for the study of valence fluctuation phenomena-application to eu-based intermetallic compounds

X-ray magnetic circular dichroism (XMCD) in Eu-based valence fluctuating compounds, EuNi₂(Si_1-x Ge _x )₂ (x=0.82, 0.85) and EuNi₂P₂ are investigated at high magnetic fields up to 40 T. Distinct two XMCD peaks corresponding to different valence states, i.e., Eu²⁺ and Eu³⁺ states are observed in EuNi₂(Si_1-x Ge _x )₂ (x=0.82) and EuNi₂P₂ at the L absorption edges (2p→5d). This suggests that the Eu 5d electrons are magnetically polarized in the both valence states. Since Eu³⁺ state has nonmagnetic ground state J=0, where J is total angular momentum, finite XMCD of Eu³⁺ state can be closely related to the magnetic polarization of the conduction electrons that is induced by the local magnetic moments of Eu²⁺ (J=7/2) state through the strong hybridization.