CRITICAL CURRENTS AND IRREVERSIBILITY LINES IN HG1-XTLXBA2(CA0.86SR0.14)(2) CU3O8+DELTA

We report the temperature and magnetic field dependences of critical c urrent densities J(c)(H, T) and the irreversibility lines H-irr(T) for Hg1-xTlxBa2(Ca0.86Sr0.14)(2)Cu3O8+delta (x = 0.0, 0.25, 0.50 and 0.75 ). The partial substitution of Tl for Hg leads to significant enhancem ent of J(c) and H-irr without changing T-c. This enhancement is attrib uted to an improvement in the flux pinning capability by the Tl doping . The temperature dependence of J(c) and H-irr follows a power law: J( c) proportional to (1 - T/T-c)(nu) and H-irr proportional to (1 - T/Tc )(alpha) with the values of nu and alpha decreasing as the Tl content increases.