Spatially-resolved studies of chemical composition, critical temperature, and critical current density of YBaCuO thin film

TL;DR

This study employs spatially-resolved techniques to analyze the chemical composition, critical temperature, and critical current density of a YBaCuO thin film, revealing correlations and effects of composition variations on superconducting properties.

Contribution

It introduces a new method to extract the critical current density distribution from magnetic flux measurements and correlates it with chemical and superconducting property variations.

Findings

Jc and Tc are correlated along the bridge.

Deviations from stoichiometry reduce Tc and Jc.

Jc profile mirrors Tc profile with additional fine structure.

Abstract

Spatially-resolved studies of a YBaCuO thin film bridge using electron probe microanalysis (EPMA), low-temperature scanning electron microscopy (LTSEM), and magneto-optical flux visualization (MO) have been carried out. Variations in chemical composition along the bridge were measured by EPMA with 3 microns resolution. Using LTSEM the spatial distributions of the critical temperature, Tc, and of the local transition width, dTc, were determined with 5 microns resolution. Distributions of magnetic flux over the bridge in an applied magnetic field have been measured at 15 and 50 K by magneto-optical technique. The critical current density Jc as a function of coordinate along the bridge was extracted from the measured distributions by a new specially developed method. Significant correlations between Jc, Tc, dTc and cation composition have been revealed. It is shown that in low magnetic fields deviation from the stoichiometric composition leads to a decrease in both Tc and Jc. The profile of Jc follows the Tc-profile on large length scales and has an additional fine structure on short scales. The profile of Jc along the bridge normalized to its value at any point is almost independent of temperature.