We have studied the multiharmonic ac susceptibility response of $\mathrm{Hg}{\mathrm{Ba}}_2{\mathrm{Ca}}_4{\mathrm{Cu}}_5{\mathrm{O}}_y$ (Hg:1245), a multilayered high-temperature superconductor (HTS) having two crystallographically inequivalent $\mathrm{Cu}{\mathrm{O}}_2$ planes in a unit cell with very imbalanced carrier concentrations. Vortex melting lines are well described by the commonly accepted model of melting with moderate anisotropy factors of 40–50, depending on the doping level. The diamagnetic response with applied fields parallel to superconducting $(a,b)$ planes also shows a quite robust supercurrent along the $c$ axis. Our results are also discussed in connection with contradictory models and experiments regarding the coexistence of superconductivity and antiferromagnetism in HTSs.

• Received 10 December 2006

DOI:https://doi.org/10.1103/PhysRevB.76.212508