title: Hierarchical dielectric orders in layered ferroelectrics Bi2SiO5.
abstract: Electric dipole engineering is now an emerging technology for high electron-mobility transistors, ferroelectric random access memory and multiferroic devices etc. Although various studies to provide insight into dipole moment behaviour, such as phase transition, order and disorder states, have been reported, macroscopic spontaneous polarization has been mainly discussed so far. Here, visualization of the electric dipole arrangement in layered ferroelectrics Bi2SiO5 by means of combined analysis of maximum entropy charge density and electrostatic potential distribution analysis based on synchrotron radiation X-ray powder diffraction data is reported. It was found that the hierarchical dipole orders, the weak-ferroelectric and ferroelectric configurations, were observed in the Bi2O2 and the SiO3 layers, respectively, and the ferrielectric configuration was realised by the interlayer interaction. This discovery provides a new method to visualize the local polarization in ferroelectric materials.
authors: Department of Advanced Materials Science, The University of Tokyo , Kashiwa, Chiba 277-8561, Japan ; RIKEN SPring-8 Center , Kouto, Sayo-cho, Hyogo 679-5148, Japan.
authors: Younghun
authors: Y
authors: Kim
authors: RIKEN SPring-8 Center , Kouto, Sayo-cho, Hyogo 679-5148, Japan ; Japan Synchrotron Radiation Research Institute , Kouto, Sayo-cho, Hyogo 679-5148, Japan.
authors: Jungeun
authors: J
authors: Kim
authors: Japan Synchrotron Radiation Research Institute , Kouto, Sayo-cho, Hyogo 679-5148, Japan.
authors: Akihiko
authors: A
authors: Fujiwara
authors: Department of Physics, Nagoya University , Furo-cho, Nagoya 464-8602, Japan.
authors: Hiroki
authors: H
authors: Taniguchi
authors: Department of Energy Science, Sungkyunkwan University , Jangan-Gu, Suwon 440-746, South Korea.
authors: Sungwng
authors: S
authors: Kim
authors: Department of Materials Science, Shimane University , 1060 Nishi-kawatsu-cho, Matsue, Shimane 690-8504, Japan.
authors: Hiroshi
authors: H
authors: Tanaka
authors: RIKEN SPring-8 Center , Kouto, Sayo-cho, Hyogo 679-5148, Japan ; Japan Synchrotron Radiation Research Institute , Kouto, Sayo-cho, Hyogo 679-5148, Japan.
authors: Kunihisa
authors: K
authors: Sugimoto
authors: RIKEN SPring-8 Center , Kouto, Sayo-cho, Hyogo 679-5148, Japan.
authors: Kenichi
authors: K
authors: Kato
authors: Materials and Structures Laboratory, Tokyo Institute of Technology , Yokohama 226-8503, Japan.
authors: Mitsuru
authors: M
authors: Itoh
authors: Materials and Structures Laboratory, Tokyo Institute of Technology , Yokohama 226-8503, Japan ; Frontier Research Center, Tokyo Institute of Technology , Yokohama 226-8503, Japan.
authors: Hideo
authors: H
authors: Hosono
authors: Department of Advanced Materials Science, The University of Tokyo , Kashiwa, Chiba 277-8561, Japan ; RIKEN SPring-8 Center , Kouto, Sayo-cho, Hyogo 679-5148, Japan ; Japan Synchrotron Radiation Research Institute , Kouto, Sayo-cho, Hyogo 679-5148, Japan.
authors: Masaki
authors: M
authors: Takata
keywords: electron charge density; electrostatic potential; hierarchical dielectric ordering; visualization of local polarization