High-Magnetic-Field X-ray Absorption Spectroscopy of Field-Induced Valence Transition in EuNi_2(Si_<1-x>Ge_x)_2(Condensed matter : electronic structure and electrical, magnetic, and optical properties)

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The magnetic-field-induced valence transition in EuNi_2(Si_<1-x>Ge_x)_2 (x = 0.82, 0.85) has been studied by X-ray absorption spectroscopy at low temperatures. The field dependence of the Eu valence is directly observed for the first time. We find a significant decrease in the valences at high magnetic fields above 40 T. The valence of Eu changes from v^* = 2.75 at a zero field to v^* = 2.33 at 40 T for x = 0.82. The results are analyzed using a theoretical model. The hybridization parameter V between the Eu^<2+> and Eu^<3+> states and the energy separation ΔE are determined, which are crucial for quantum mechanical mixing.
社団法人日本物理学会の論文
2008-05-15