Current transfer in grain-boundary junctions of Bi(Pb)SrCaCuO thick films

Abstract

This paper is devoted to the experimental study of the mechanism of energy dissipation caused by DC transport currents in superconducting Bi(Pb)SrCaCuO screen-printed films. Current-voltage characteristics were measured by the standard four-probe method, and their magnetic field and temperature dependence for different film widths was systematically investigated. The magnetic field and temperature ranged from 0 to 10 mT and from 4.5 to 120 K. Some peculiarities of the current-voltage characteristics were observed. Josephson-type vortex-antivortex pairs were generated at the edges of the film and they slip into the inner part of the film resulting in energy dissipation. This phenomenon appeared in the current-voltage characteristics as a linear part. The evaluation of the film width dependence of the critical current made it possible to calculate the Josephson penetration depth with the numerical result: λ j ∼50μm. At higher currents the voltage increased much faster than in the linear part and the characteristics became strongly nonlinear. A clear distinction could be made between the critical-current limitation caused by flux motion and that, at which the curve started to be nonlinear. The difference between these two dissipation mechanisms was demonstrated by quantum interference patterns observed in the nonlinear section of the current-voltage curves.