Study of Local Atomic Structures of Sm Doped YbB<sub>6</sub> Observed by X-ray Fluorescence Holography

We performed X-ray fluorescence holography experiments in Sm-doped YbB6 with a boron cage structure to determine whether the difference of ionic radii of Sm3+ and Yb2+ affects the Yb lattice. We found that the intensity of the Yb atomic image around the doped Sm is in good agreement with the simulation. These results suggest that Sm doping does not cause fluctuations or distribution in the Yb lattice outside the boron cage because of the strong covalent bonds in the three-dimensional boron cage network. In contrast, the first nearest-neighbor (NN) Yb around Sm is shifted outward by approximately 0.2 Å from Sm, implying that the doped trivalent Sm pushes the first NN Yb out while maintaining a particular distance from Sm without fluctuation or distribution.