Magnetoresistance Studies of Tl-1223 Phase Substituted byScandium

摘要

Superconducting samples of type T1Ba_2Ca_(2-x)Sc_xCu_3O_(9-δ) with x = 0.0, 0.025, 0.05, 0.1, and 0.2 have been prepared via 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 AT with increasing magnetic fields. The experimental data 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~(-β). Also, the transition width is related to the magnetic field according to the relation △T α B~n. The values of β and n are strongly dependent on the Scandium-content. The temperature and magnetic field dependence of the activation energy U(B, T) is found to be U( B, T) ～ △T B~(-η), where η = β + 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 κ_e, estimated from Wiedemann-Franz law, is reported at different applied magnetic fields for the prepared samples.