X-Ray Diffuse Scattering Study on Ionic-Pair Displacement Correlations   in Relaxor Lead Magnesium Niobate
  Ionic-pair equal-time displacement correlations in relaxor lead magnesium niobate, $Pb(Mg_{1/3}Nb_{2/3})O_{3}$, have been investigated at room temperature in terms of an x-ray diffuse scattering technique. Functions of the distinct correlations have been determined quantitatively. The results show the significantly strong rhombohedral-polar correlations regarding Pb-O, Mg/Nb-O, and O-O' pairs. Their spatial distribution forms an ellipse or a sphere with the radii of 30-80$\AA$. This observation of local structure in the system proves precursory presence of the polar microregions in the paraelectric state which leads to the dielectric dispersion. 
Naohisa Takesue (Issp, U. of Tokyo), Yasuhiko Fujii (ISSP, U. of To   kyo), and Hoydoo You (Argonne National Lab.)