X-ray scattering study of two length scales in the critical fluctuations   of CuGeO3
  The critical fluctuations of CuGeO$_3$ have been measured by synchrotron x-ray scattering, and two length scales are clearly observed. The ratio between the two length scales is found to be significantly different along the $a$ axis, with the $a$ axis along the surface normal direction. We believe that such a directional preference is a clear sign that surface random strains, especially those caused by dislocations, are the origin of the long length scale fluctuations. 
Y.J. Wang, Y.-J. Kim, R.J. Christianson, S.C. LaMarra, F.C. Chou, and   R.J. Birgeneau