Magnetoresistance studies of Tl-1212 phase substituted by scandium

Superconducting samples of TlBa2CaCu2-xScxO7-delta with x = 0.0, 0.025, 0.05, 0.1, 0.15 and 0.2 have been prepared via the solid-state reaction technique. The effect of weak magnetic fields up to 4.4 kG on the electrical resistivity of the prepared samples has been studied to investigate the flux motion for this phase. The results reveal a slight shift in the superconducting transition temperature T-c and an increase in the superconducting transition width Delta T with increasing magnetic field. The magnetic field has a small effect on the electrical resistivity in the normal state and in the first stage of transition, whereas the change in the second stage of superconducting transition is very large. The experimental data, in the second stage of superconducting transition, fit well with the thermally activated flux creep model and the activation energy U(B) shows a power law dependence on magnetic field as B-beta. Also, the transition width is related to the magnetic field according to the relation Delta T alpha B-n. The values of beta and n are strongly dependent on the scandium content. The magnetic field and temperature dependence of the activation energy U(B, T) is found to be U(B, T) similar to Delta T B-eta, where eta = beta + n. The critical current density J(c)(0) and the upper critical field B-c2(0) are calculated, from the above measurements, as a function of scandium content. Finally, the electronic thermal conductivity kappa(e), estimated from the Wiedermann-Franz law, is reported at different applied magnetic fields for the prepared samples.