Temperature dependence of pinning potentials in grain-aligned and Re-doped Hg-1223 superconductors

Abstract

Effect of grain alignment and Re-doping on the flux-creep phenomena in Hg-1223 superconductors is investigated. Hg-based superconductors of HgBa 2Ca 2Cu 3Re x O y ( x = 0.15 and 0.18) were fabricated by high vacuum sealing and sintering method using a precursor. Grain alignment was formed magnetically under external magnetic field of 10 T. Connectivity between the superconducting CuO 2 layers is known to be enhanced with addition of Re. Flux creep characteristics and DC magnetizations were measured using a SQUID magnetometer at temperature range 5–150 K under magnetic fields up to 1 T. The pinning potentials U 0 ∗ estimated from the logarithmic time dependence of the magnetization for B∥ ab are generally larger than those for B∥ c. Non-linear relation of pinning barrier energy U( J) on current density J leads to apparently low energy in the high J region which is remarkable at low temperatures. Independence of the U 0 ∗ on the applied fields B∥ c in this region and increase of the U 0 ∗ with lowering B∥ ab indicate the difference of non-linearity. In addition, temperature dependence of the flux creep rate S is favorably compared with the Anderson–Kim model.