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Kohara, Shinji*; Oishi, Yasuo*; Takata, Masaki*; Yoneda, Yasuhiro; Suzuya, Kentaro
Nihon Kessho Gakkai-Shi, 47(2), p.123 - 129, 2005/04
The use of high-energy (E 
50 keV) X-rays from SPring-8 allows us to perform X-ray diffraction experiments on disordered materials with the following advantages: high resolution in real space due to the wide range of scattering vector, small correction terms (particularly the absorption correction), and fast diffraction measurement with small amount of samples. Recently, high-energy X-ray diffraction data have been combined with neutron diffraction data from a pulsed neutron source to provide more detailed and reliable structural information than has hitherto been available. Furthermore, the use of reverse Monte Carlo modelling and PDF (pair distribution function) simulation based on high-energy X-ray diffraction data have succeeded in illustrating 3-dimensional structure of disordered materials and disorder in crystalline materials.
SbTe
Shamoto, Shinichi; Yamada, Noboru*; Matsunaga, Toshiyuki*; Proffen, T.*; Richardson, J. W.*; Chung, J.-H.*; Egami, Takeshi*
Applied Physics Letters, 86(8), p.081904_1 - 081904_3, 2005/02
Times Cited Count：48 Percentile：81.94(Physics, Applied)Local structure of NaCl-type crystalline GeSbTe has been studied by the atomic pair distribution function analysis of pulsed neutron powder diffraction data. We have found the large displacement of germanium atoms in this crystalline phase. Usually, such a large lattice distortion has disadvantage for the electric conductivity. The electronic band structure, however, implies that this significant distortion in addition to the lattice defect at Na site reduces only thermal conductivity, while the highly ordered tellurium atoms at Cl site keep high electric conductivity.
studied by neutron diffractionChung, J.-H.*; Proffen, T.*; Shamoto, Shinichi; Ghorayeb, A. M.*; Croguennec, L.*; Tian, W.*; Sales, B. C.*; Jin, R.*; Mandrus, D.*; Egami, Takeshi*
Physical Review B, 71(6), p.064410_1 - 064410_11, 2005/02
Times Cited Count：77 Percentile：90.04(Materials Science, Multidisciplinary)LiNiO (S=1/2) forms a triangular lattice with the possible magnetic frustration, but the exact state of spin correlation has not yet been known. While there is no signature of long-range Jahn-Teller distortion, local JT distortion has been suspected. We have performed neutron diffraction and atomic pair-density function analyses up to unprecedented large distances to discover a number of unusual features, such as anomalous peak broadening, local JT distortion, sharp oxygen-oxygen distance correlations, and inverted temperature dependence of medium range correlation. These observations are best explained by local orbital ordering of Ni
ions into three sublattices. This orbital ordering, however, cannot develop into long-range order because of the strain field it generates, and domains of about 10 nm in size are formed. Domains are susceptible to random pinning by impurities ssite disorderd resulting in the loss of structural long-range order. We suggest that this local orbital ordering is the basis for the complex magnetic properties observed in this compound.
Shamoto, Shinichi
no journal, ,
Functional materials often have disordered lattice structures. As the examples, optical phase change material and negative thermal expansion material studied by the atomic pair distribution function analysis are discussed in the relation with their electronic structures.
Shamoto, Shinichi
no journal, ,
no abstracts in English
Shamoto, Shinichi
no journal, ,
Some modern functional materials have crystal structures with hidden lattice distortions, which play an important role for their functions. The atomic pair distribution function (PDF) analysis can be applied to reveal these lattice distortions.
Shamoto, Shinichi
no journal, ,
Various states have been discovered between liquid and solid phases like a liquid crystal even in an inorganic solid. This aspect can be extended from a simple solid-state to various nanoscaled states with partial ordering.
