Concerning Order and Disorder in the Ensemble of Cu-O Chain Fragments in Oxygen Deficient Planes of Y-Ba-Cu-O

TL;DR

This paper investigates the disorder and ordering of Cu-O chain fragments in oxygen-deficient Y-Ba-Cu-O high-temperature superconductors, analyzing how oxygen disorder affects structural properties through theoretical modeling and diffraction data.

Contribution

It introduces a theoretical approach to quantify oxygen disorder and its impact on the structure factor in YBCO, focusing on the orthorhombic phase and chain fragment correlations.

Findings

Correlation lengths depend on oxygen disorder and annealing temperature.

Numerical calculations visualize the evolution of the structure factor with oxygen content.

Theoretical results align with diffraction data on Cu-O chain disorder.

Abstract

In connection with numerous X-ray and neutron investigations of some high temperature superconductors (YBa$_2$Cu$_3$O$_{6+x}$ and related compounds) a non-trivial part of the structure factor, coming from partly disordered Cu-O-$\dots$-O-Cu chain fragments, situated within basal planes, CuO$_x$, can be a subject of theoretical interest. Closely connected to such a diffusive part of the structure factor are the correlation lengths, which are also available in neutron and X-ray diffraction studies and depend on a degree of oxygen disorder in a basal plane. The quantitative measure of such a disorder can be associated with temperature of a sample anneal, $T_q$, at which oxygen in a basal plane remains frozen-in high temperature equilibrium after a fast quench of a sample to room or lower temperature. The structure factor evolution with $x$ is vizualized in figures after the numerical calculations. The theoretical approach employed in the paper has been developed for the orthorhombic state of YBCO.