Anisotropic dynamical scaling in a weakly 3D system: The case of oxygen ordering in YBa2Cu3O6.5

The coarsening of anisotropic oxygen superstructure domains of the Ortho-II type in YBa2Cu3O6.5 has been investigated by high-energy X-ray and neutron diffraction. The time dependence of the scattering function S(q,t) was pro bed after quenches through the Ortho-II phase transition, and by room tempe rature measurements of S(q) after various sample annealing histories. The d ata are well accounted for by a Lorentzian-squared-type scattering function . In agreement with the scaling hypothesis, we find that the integrated int ensity is independent of time, and the domain growth is described by a sing le scalar function that characterise the time evolution of the anisotropic correlation lengths. We have thus for the first time demonstrated the appli cability of the dynamical scaling hypothesis in a real system of high compl exity and intermediate dimensionality.