Local structure study about Co in YBa$_2$(Cu$_{1-x}$Co$_x$)$_3$O$_{7-\delta}$ thin films using polarized XAFS

TL;DR

This study investigates the local atomic structure around cobalt in YBCO thin films using polarized XAFS, revealing well-ordered oxygen neighbors with shortened bond lengths and increased disorder compared to powder samples.

Contribution

First detailed polarized XAFS analysis of Co local environment in YBCO thin films, highlighting differences from powder samples and providing insights into local structural distortions.

Findings

Oxygen neighbors are well ordered with shortened bond lengths.

Cobalt environment shows more disorder in thin films than in powders.

Bond lengths are 1.80 Å (c-axis) and 1.87 Å (ab-plane).

Abstract

We have studied the local structure around Co in YBa$_2$(Cu$_{1-x}$Co$_x$)$_3$O$_{7-\delta}$ thin films with three different concentrations: x=0.07, 0.10, 0.17, and in a PrBa$_2$(Cu$_{1-x}$Co$_x$)$_3$O$_{7-\delta}$ thin film of concentration x=0.05 using the X-ray Absorption Fine Structure (XAFS) technique. Data were collected at the Co $K$-edge with polarizations both parallel and perpendicular to the film surface. We find that the oxygen neighbors are well ordered and shortened in comparison with YBCO Cu-O values to 1.80 \AA{} and 1.87 \AA{} in the $c$-axis and $ab$-plane, respectively. A comparison of further neighbors in the thin film and powder data show that these peaks in the film are suppressed in amplitude relative to the powder samples, which suggests there is more disorder and/or distortions of the Co environment present in the thin films.