Simple solution to problems concerning oxygen ordering inYBa2Cu3O6+x

Abstract

Analysis of a simple extension of the ASYNNNI model rationalizes several hitherto unexplained structural observations of the oxygen ordering in ${\mathrm{YBa}}_{2}{\mathrm{Cu}}_{3}{\mathrm{O}}_{6+x}:$ the existence of ortho-III, ortho-V, and ortho-VIII phase correlations; suppression of the ortho-I-ortho-II transition temperature relative to that of the tetragonal-ortho-I transition; no ortho-II Bragg peaks, but a crossover from Lorentzian towards Lorentzian squared line shapes; the average chain length. It yields a realistic picture of the oxygen order of importance for the understanding of the hole doping.