Critical currents and irreversibility lines in Hg 1− xTl xBa 2(Ca 0.86Sr 0.14) 2Cu 3O 8+δ

Abstract

We report the temperature and magnetic field dependences of critical current densities J c ( H, T) and the irreversibility lines H irr ( T) for Hg 1− x Tl x Ba 2(Ca 0.86Sr 0.14) 2Cu 3O 8+δ ( x = 0.0, 0.25, 0.50 and 0.75). The partial substitution of Tl for Hg leads to significant enhancement of J c and H irr without changing T c . This enhancement is attributed 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 α (1 − T T c ) ν and H irr α (1 − T T c ) α with the values of ν and α decreasing as the Tl content increases.