Abstract
We have studied the magnetic and transport properties of granular samples of the electron-doped superconductor Sm 1.83Ce 0.17CuO 4− y prepared under certain conditions. Measurements of magnetic susceptibility, electrical resistance and magnetoresistance in applied magnetic fields up to 8.8 T reveal that superconductivity develops below T ci ≈ 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, ΔR( 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 increase of ΔR close to T ci is due to the depletion of the concentration of normal carriers as predicted by the semi-phenomenological two-fluid theory of superconductivity. The behaviour of ΔR at lower temperatures is also discussed.
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