Simple solution to problems concerning oxygen ordering inYBa2Cu3O

Abstract

Analysis of a simple extension of the ASYNNNI model rationalizes several hitherto unexplained structural observations of the oxygen ordering in YBa 2 Cu 3 O 6ϩx : 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 tetragonalortho-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.

Light-induced oxygen-ordering dynamics in(Y,Pr)Ba2Cu3OBahrs1, Goñi2, Thomsen3 et al. 2004Phys. Rev. B152160View full textAdd to dashboardCite

“…We base our calculations on this setup, although there has been much work on a more detailed description. [23][24][25][26][27] The dynamical properties of the ASYNNNI model and oxygen reordering have been studied in detail in Refs. [35][36][37][38], focusing on the range of thermally induced reordering above room temperature.…”

“…It has been shown that ordered superstructure patterns of full and empty chains in the chain plane are energetically favorable and provide a higher doping level of the superconducting planes than statistically distributed vacancies. 8 The structural phase diagram of YBa 2 Cu 3 O 7−␦ has been simulated with the Monte Carlo based asymmetric next nearest neighbor Ising (ASYNNNI) model as developed, e.g., by Andersen et al 5,[23][24][25][26][27] For spontaneous oxygen reordering above room temperature, x-ray and neutron diffraction provide direct evidence for the link of transport properties to axis shortening and superstructure development. [2][3][4][5] Both pressure and illumination reduce the c-axis length and increase the critical temperature due to the charge transfer they induce.…”

Superconducting Materials — A Topical Overview

“…The c-axis lattice parameter of these SC Pr-123 samples fits well in the series of the other SC RE-123 compounds, in remarkable contrast to the c-axis lattice parameter of the usual non-SC Pr-123 samples [126,127] where the absence of superconductivity is attributed to a hybridisation of the Pr 4f electrons with O 2p electrons depriving mobile charge carriers [128,129]. 21 The microscopic distribution of oxygen [111] is neither easily observed [112,113,114] nor easily controlled [115]: Experimentally, oxygen content and distribution are adjusted by means of (oxygen partial) pressure, temperature and sufficient holding time to achieve thermal equilibrium [116]. 22 The T c depression is believed to arise from a redistribution of doping charge in the CuO 2 layer stacks from the interior to the outer CuO 2 layers [117] which has been confirmed by NMR measurements [118,119].…”

Calculation of combinative energy between perovskite and rocksalt blocks inYBa2Cu3OZhang1, Cheng2, Zhao3 2000Phys. Rev. B17030View full textAdd to dashboardCite

“…1, the difference between the three curves is very small. Accordingly, it is supposed that the plateau at about 60 K is not caused by the phase transformation from the orth I to orth II, but the native properties of 11 The result in the present work just gives some hints to reconsider the role of the order of oxygen defects and its effect on superconductivity in YBa 2 Cu 3 O 7Ϫ␦ . This problem should be studied further.…”