MS39-P03 Local structure observation of Sm doped RB6 (R: rare earth)by white neutron atomic resolution holography Physical properties of materials are often controlled by impurity doping. Thus, understanding the local structures such as distorted structures around the dopant is important to clarify origins of the properties. However, such local structures cannot be observed by diffraction because there is no translational symmetry.
Recentry, atomic resolution holography using x-rays and photoelectrons has been depeloped, which can observe local structures around dopants in the range of 20 Å of three-dimensional area. Thus, atomic resolution holography is the best probe to investigate local structures.
On the other hand, it is difficult to observe light elements such as H, B or O by x-rays and photoelectrons. Therefore, we have developed atomic resolution holography using white neutrons, which are sensitive to light elements, at Japan-Proton Accelerator Research Complex at Tokai Japan . We have already succeeded in visualising local atomic structure in B doped Si, which is the most important semiconductor, and Eu 1% doped CaF2, which is a typhical scintilation crystal. For CaF2, we found that there exist excess F around doped Eu . Based on this success, we are trying to apply this novel technique to various fields of materials science.
In this study, we focus on a strongly correlated electron system RB6 (R: rare earth). When Sm is doped in LaB6 and YbB6, it behaves as Sm2+ in the former and as Sm3+ in the latter . We expect that the difference of local structures around Sm may play a role in this change of valency. White neutron holography experiments were performed on a single crystal La11B6 and Yb11B6 with 2% doped Sm. We succeeded in reconstruction of the local structure of R around Sm using data in the neutron energy range from 10 meV to 200 meV. We confirmed that R around the Sm dopant are located at the same positions as in pure RB6, meaning that Sm doping does not effect R structure. Moreover, we also succeeded in reconstruction local structure of 11B viewed from Sm. These results indicate that neutron atomic resolution holography is an effective probe for investigations of local structures even for various materials which include light elements.
 K. Hayashi, et al., (2017) Sci. Adv, 3, e1700294.
 J.M. Trascon, et al., (1980) J. Physique, 41, 1135.Keywords: Neutron, Local structure, Holography