RESISTIVE MEASUREMENT OF THE TEMPERATURE-DEPENDENCE OF THE PENETRATION DEPTH OF NB IN NB/ALOX/NB JOSEPHSON-JUNCTIONS

The temperature dependence of the penetration depth of Nb films was determined from resistive transitions of Nb/AlO(x)/Nb Josephson junctions in a constant magnetic field applied parallel to the junction planes. Distinct resistance peaks were observed as temperature decreases and those peaks were found to appear when the total flux threading the junction equals an integral multiple of the flux quantum. From this condition, the penetration depth at those peak positions has been determined. The temperature dependence was well described by either the dirty local limit or the two-fluid model. This method can be useful for a highly fluctuating system such as high-temperature superconductors.