Temperature dependence of Nb penetration depth measured by a resistive method

Besides the conventional method of measuring the penetration depth of Nb superconductors in Nb/AlOx/Nb Josephson junction, a simple resistive method is applied in this study. With the applied magnetic field parallel to the junction plane, resistive measurement of resistance–temperature characteristics in a given magnetic field or resistance–magnetic field curves at a fixed temperature show resistance peaks whenever the total magnetic flux through the junction equals an integral multiple of the flux quantum. We demonstrate how to determine the penetration depth from such measurements and discuss its temperature dependence in terms of fundamental film properties.