Critical currents of (Tl0.5Pb0.5)(Sr0.85Ba0.15)2Ca2Cu3Oz films on untextured silver substrates

Superconducting (TI0.5Pb0.5)(Sr0.85Ba0.15)(2)Ca2Cu3Oz films were prepared on highly polished, untextured silver substrates. A superconducting transition temperature (T-c) of 114.9 +/- 0. 1 K was obtained from the resistivity versus temperature measurements for different applied ac currents. The temperature dependence of the critical current was fitted with a power law: J(c)(T)=J(c)(0)[1 - T/T-c](n) with n = 2. The critical current in self-field at 77 K was found to be 8 x 10(3) A/cm(2). The temperature dependence of the real and imaginary parts of ac susceptibility was measured for different amplitudes of ac magnetic field. Only a small differences of the ac susceptibility for parallel and perpendicular fields with respect to the film surface were observed. (C) 2007 Elsevier B.V. All rights reserved.