Critical currents and flux creep in low Tc Pb/Ge multilayers

Magnetization studies of critical currents Jc(Hperpendicularto,T) and of the flux creep rate dlnM/dlnt have been carried out on low Tc Pb/Ge multilayers, which can be used to model the superconducting properties of the layered high Tc cuprates. By taking a proper Ge separator thickness a crossover between two different pinning regimes can be observed. This transition leads to an anomalous dependence of critical current and the flux creep rate on perpendicular magnetic field Hperpendicularto in Pb/Ge multilayers, while a single Pb film demonstrates a monotonous suppression of Jc by Hperpendicularto. These magnetization data fully confirm the anomalous behaviour of Jc(Hperpendicularto) previously found in Pb/Ge multilayers from measurements of transport critical current. (orig.)