The Re-doped high T-c superconductor HgBa2Ca2Cu3Ox: Magnetic irreversibility versus anisotropy

We report on magnetization measurements on grain-aligned Re-doped Hg-1223 s uperconductor (T-c approximate to 133 K). We analyze the anisotropic magnet ic hysteresis M-irr as a function of temperature and magnetic field, and de termine the irreversibility line H-irr(T) for magnetic fields applied paral lel and perpendicular to the c axis of the structure. The similar values of both M-irr and H-irr(T) along the two main crystallographic directions rev eal a marked decrease of the superconducting anisotropy, due to the Re subs titution. This anisotropy reduction might be at the origin of the rise of t he magnetic irreversibility already reported in these compounds, as compare d to those without Re. (C) 1998 American Institute of Physics.