Flux focusing effects in planar thin-film grain-boundary Josephson junctions

Abstract

We have studied the magnetic interference of the critical currents of synthetic planar thin-film grain-boundary Josephson junctions. We find that the effective area of these junctions scales as the square of the width w in contrast to the usual w(2λ+d) dependence of sandwich-type Josephson junctions. This behavior is a simple consequence of the magnetic response of thin-film superconductors to perpendicular applied fields. A model based on the London theory yields the observed behavior. In addition, we find the correction to the interference pattern due to the effect of the corners.