INFLUENCE OF THE INTERFACE ROUGHNESS OF J(C) OF GE PB/GE SANDWICHES/

Critical current densities J(c) for fields applied perpendicular to MB E prepared Ge/Pb/Ge sandwiches and bare Pb films have been obtained fr om magnetization measurements. The single Pb film shows smooth magneti zation loops at all temperatures and a monotonous decrease of J(c) wit h rising temperature. The Ge/Pb/Ge sandwiches reveal peaks in the magn etization curves at lower temperatures and become smooth only in the v icinity of T(c) (congruent-to 7K). J(c)(T) for the sandwiches shows a well defined maximum at approximately 5K. As a result, the J(c) values of this sandwich are increased by a factor of 3 in the temperature ra nge 5-7K. This different behaviour may be due to enhanced pinning at t he Ge-Pb interfaces, which were studied using Atomic Force Microscopy (AFM).