FIELD AND TEMPERATURE-DEPENDENT SURFACE-RESISTANCE OF SUPERCONDUCTING POLYCRYSTALLINE MULTIPLE-PHASE HG-BA-CA-CU-O - EVIDENCE FOR DIRTY-LIMIT BEHAVIOR

Field- and temperature-dependent surface resistance measurements at 12.9 GHz are reported for polycrystalline Hg-Ba-Ca-Cu-O, which was found to consist primarily of the HgBa2CaCu2O6+δ and HgBa2Ca2Cu3O8+δ phases. A small amount of a third phase, most likely HgBa2Ca3Cu4O10+δ, was also detected. With variation of the angle Ψ between the applied field and current density, the low-temperature data exhibit large flux-flow resistivity that varies approximately as sin2(Ψ), while at high temperatures, the dominant field- and temperature-dependent response is attributed to isotropic phase-slip losses in intragranular defects. For temperatures just below the transition temperature of the two-layer phase, very small flux flow is evidenced. This result is consistent with an effective Hc2 of unusual size, suggesting a dirty-limit value for Hc2. © 1995 The American Physical Society.