INCREASED RESISTANCE BELOW THE SUPERCONDUCTING TRANSITION IN GRANULARSM1.83FE0.17CUO4-Y COMPOUNDS

We have studied the magnetic and transport properties of granular samp les of the electron-doped superconductor Sm1.83Ce0.17CuO4-y prepared u nder certain conditions. Measurements of magnetic susceptibility, elec trical resistance and magnetoresistance in applied magnetic fields up to 8.8 T reveal that superconductivity develops below T-ci approximate to 17.5 K in these compounds. We also observed an abrupt increase of the electrical resistance below the superconducting transition. It was found that the resistance excess, Delta R(T,H), is proportional to (T /T-ci)(-4) close to T-ci, 0.6 < (T/T-ci)<1, and shows a crossover to a (T/T-ci)(-1/4) dependence at lower temperatures. We argued that the i ncrease of Delta R close to T-ci is due to the depletion of the concen tration of normal carriers as predicted by the semi-phenomenological t wo-fluid theory of superconductivity. The behaviour of Delta R at lowe r temperatures is also discussed. (C) 1997 Elsevier Science B.V.