Spatially resolved studies of chemical composition, critical temperature, and critical current density of a YBa2Cu3O7−δ thin film

Spatially resolved studies of a YBa2Cu3O7−δ thin film bridge using electron probe microanalysis (EPMA), low-temperature scanning electron microscopy (LTSEM), and magneto-optical flux visualization have been carried out. Variations in chemical composition along the bridge were measured by EPMA with 3 μm resolution. Using LTSEM the spatial distributions of the critical temperature, Tc, and of the local transition width, ΔTc, were determined with 5 μm resolution. Distributions of magnetic flux over the bridge in an applied magnetic field have been measured at 15 and 50 K by the 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, ΔTc 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 profi...