Magnetic field induced broadening of the resistive transition in epitaxial c-axis-oriented HgBa2CaCu2O6+δ films

Abstract

The resistive transition in epitaxial c‐axis‐oriented HgBa₂CaCu₂O_6+δ (Hg‐1212) thin films T_c∼122 K) in magnetic fields up to 9 T have been investigated. A considerably larger broadening of the resistive transition is observed for magnetic fields perpendicular to the ab plane than for fields parallel to the ab plane. Over the measured range of magnetic fields, the resistivity exponentially approaches zero as a function of decreasing temperature, suggesting a thermally activated flux creep behavior. The anisotropic characteristics of Hg‐1212 are compared with other high‐temperature cuprate superconductors and found to be less than for the Bi or Tl two‐layer systems, but still considerably larger than for YBa₂Cu₃O_7−δ. This can be qualitatively explained on the basis of the differences in the insulator spacing layer thickness between the adjacent CuO₂ layers in these cuprates.