GIANT RESISTIVE PEAK CLOSE TO THE SUPERCONDUCTING TRANSITION IN L2-XCEXCUO4 SINGLE-CRYSTALS

We have measured the magnetoresistivity of some L2-xCexCuO4-y (L = Pr,Nd,Sm) superconducting single crystals along the ab plane and the c axis. For most crystals the resistivity along both directions displays a very sharp rise just below T(c) and before the zero-resistance state is reached. This resistance anomaly is quenched by a magnetic field. The effect of the field is more pronounced for H parallel-to c than for H parallel-to (ab). Several possible scenarios to account for the resistance anomaly are discussed. We propose that the resistance peak is a manifestation of a quasireentrant behavior resulting from an intrinsic granularity of these n-type high-temperature superconductors. The relevance of these results and ac susceptibility measurements for the anomalous behavior reported for the upper critical field is discussed.