Anisotropic dynamical scaling in a weakly 3D system: The case of oxygen ordering in YBa₂Cu₃O_6.5

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 probed after quenches through the Ortho-II phase transition, and by room temperature measurements of S(q) after various sample annealing histories.

The data are well accounted for by a Lorentzian-squared–type scattering function. In agreement with the scaling hypothesis, we find that the integrated intensity is independent of time, and the domain growth is described by a single scalar function that characterise the time evolution of the anisotropic correlation lengths.

We have thus for the first time demonstrated the applicability of the dynamical scaling hypothesis in a real system of high complexity and intermediate dimensionality.