The critical fluctuations of ${\mathrm{CuGeO}}_3$ 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 random surface strains, especially those caused by dislocations, are the origin of the long length scale fluctuations.

• Received 20 April 2000

DOI:https://doi.org/10.1103/PhysRevB.63.052502