OBSERVATION OF GRANULAR SUPERCONDUCTIVITY IN POLYCRYSTALLINE SM2-XCEXCUO4-Y

Using field-dependent (0 less than or equal to B less than or equal to 7 T) noncontact rf surface-resistance measurements, we confirm the on set of granular superconductivity in the high-temperature superconduct or Sm2-xCexCuO4-y, 0.15 less than or equal to x less than or equal to 0.18 at temperatures for which there is no evidence for a bulk Meissne r effect. The surface-resistance data are described with an extended f orm of the Coffey-Clem theory. For the samples with x=0.15, these meas urements also indicate that near the mean-field critical temperature T -c, -dB(c2)(c)/dT congruent to 0.38 T/K, for B parallel to c axis. [S0 163-1829(98)04606-2].