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(Si1−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(Si1−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.