Irreversibility and transport in the high Tc superconductor HgBa2Ca2Cu3O8 + δ

A HgBa 2 Ca 2 Cu 3 O 8 + δ superconductor, having a T c of 133 K (oxygen-annealed sample), was successfully synthesized. A.c. susceptibility, electrical resistivity and critical current density measurements were performed. The irreversibility line (IL) was obtained and a new feature of 1 − t ∝ H 1/4 (t = T irr /T c is the reduced temperature, where irr is the irreversibility temperature) was found and explained in terms of T. Matsushita's theory. The results of the transport measurements can be looked upon as evidence that there also might be a vortex glass-liquid transition in Hg-based systems. The dimensions of the superconducting CuO 2 layer for different compounds was used to explain the observed transition in the IL.