Electrical transport and magnetisation measurements on a 3D disordered superconductor-normal-metal composite

The preparation and superconducing properties of a disordered 3D superconductor-normal-metal composite are described. The composite consists of spherical micrometre-sized grains of Pb with a typical separation of 10 μ embedded in a very pure Al matrix. The composite exhibits bulk diamagnetism and zero resistance well above the transition temperature of the Al matrix, and has a well defined critical current which varies exponentially with temperature. The effect of a magnetic field on the electrical transport properties is examined and discussed, as is the nature of the superconducting and dissipative states. (author)