Critical Currents and Magnetization of a (Tl0.5Pb0.5)(Sr0.85Ba0.15)2Ca2Cu3Oz Film on Silver Substrate

A thin film of a (Tl0.5Pb0.5)(Sr0.85Ba0.15)2Ca2Cu3Oz superconductor was prepared on highly polished silver substrate. Its superconducting transition temperature (Tc,50%) is 114.7 +- 0.3 K and the critical current density is 11.4 x 103 A/cm2 at 77 K in self field. The transport critical currents densities were measured as a function of temperature for several applied magnetic fields. The magnetization versus the dc applied magnetic field and temperature was also measured and the critical current densities were calculated. The temperature dependence of the critical currents obeys the Ginzburg-Landau power-law. Reasons for this behavior were discussed taking into account the pining force and anisotropy of the critical currents associated with the c-axis grain orientation of the film. The magnetization as a function of the angle between the applied magnetic field and the a-b plane showed a periodic dependence due to changes of the demagnetizing field.