Superconductor strip with transport current: Magneto-optical study of current distribution and its relaxation

The dynamics of magnetic flux distributions across a YBaCuO strip carrying transport current is measured using magneto-optical imaging at 20 K. The current is applied in pulses of 40-5000 ms duration and magnitude close to the critical one, 5.5 A. During the pulse some extra flux usually penetrates the strip, so the local field increases in magnitude. When the strip is initially penetrated by flux, the local field either increases or decreases depending both on the spatial coordinate and the current magnitude. Meanwhile, the current density always tends to redistribute more uniformly. Despite the relaxation, all distributions remain qualitatively similar to the Bean model predictions.Comment: RevTeX, 9 pages, 9 figures, submitted to Supercond. Sci. Technol. Revision: MO image and more refs are adde

Influence of layer interface parameters on dielectric characteristics of BSTO ferroelectric film planar capacitors

Ferroelectric BaxSr1-xTiO3 (BSTO) films were prepared on sapphire (r-cut) and MgO substrates using two preparation processes- RF sputtering aid the sol-gel rnethod. The structure of the films and interfaces were investigated by middle energy ion back scattering combined with ion channelling. Planar capacitors patterned on the film allowed the temperature dependence of capacitance and voltage-capacitance characteristics (VCC) to be measured at a frequency of 1 MHz. The influence of some interface parameters (e.g. the presence of intermediate layers, structural ordering of the BSTO surface layer, the type of film electrode) on dielectric characteristics, VCC hysteresis and tunability of the planar capacitors are discussed