MAGNETIZATION AND RESISTIVITY STUDY ON THE 130-K SUPERCONDUCTOR IN THE HG-BA-CA-CU-O SYSTEM

Samples containing superconducting HgBa2Ca2Cu3O8+x (Hg-1223) (a=3.851 (3) angstrom, c=15.847 (9) angstrom) as the dominant phase have been i nvestigated by resistivity and magnetization measurements in external magnetic fields up to 50 kOe. The specimens exhibit critical temperatu res T(c) almost-equal-to 133 K, as measured by susceptibility and spec ific-heat experiments, with typical field-cooling susceptibilitieS chi (FC) > 20% of -1/4pi at low temperatures. In zero field, the electrica l resistance is zero below T=129 K. From magnetization-loop, M(H), mea surements and the broadening of the resistive transition in external m agnetic fields, H, we estimate the location of the irreversibility bou ndary H(irr)(T) in the magnetic phase diagram of the material. Estimat es of the critical-current densities j(c) in a magnetic field for T=10 K and 75 K suggest that the intragrain critical-current densities are of comparable order of magnitude to those routinely observed in YBa2C u3O7 at those temperatures.