Yb LIII-edge and Cu K-edge x-ray absorption spectroscopy in YbCdCu4 and YbInCu4

The electronic structures of YbCdCu4 and YbInCu4 have been studied by X-ray absorption spectroscopy at room tem- perature. We have observed a shoulder structure at 8940 eV on the low-energy side of the Yb3+ component in the Yb LIII-edge. This structure is assigned to the LIII transitions of the Yb2+ electronic state, and thus a mixing of the divalent and trivalent states can be expected in both YbCdCu4 and YbInCu4. The energy position of the Cu K-edge coincides with that of Cu2O as reference materials for the 3d10 electron configuration. Our results suggest that the electron configurations of Yb and Cu ions for YbCdCu4 are similar to that for YbInCu4 in the high-temperature phase.