Properties, magnetic susceptibility, critical currents and irreversibility fields of (Tl_0.5Pb_0.5)Sr₂(Ca_1−xGd_x)Cu₂O_zbulk superconductors

Abstract

Bulk (Tl0.5Pb0.5)Sr2(Ca1−xGdx)Cu2Oz superconductors with x = 0.1,0.2 and 0.3 were prepared by a wet chemical gel technique followed by a special heat-treatment procedure. X-ray diffraction analysis revealed practically phase-pure samples with tetragonal structure (space group P/4mmm). The temperature dependence of the real and imaginary parts of the ac susceptibility and the dependence on the ac applied magnetic field were investigated to learn about the superconducting and magnetic properties of bulk (Tl0.5Pb0.5)Sr2(Ca1−xGdx)Cu2Oz superconductors. The critical current densities of the samples were derived from Bean’s model. The temperature dependence of the critical current was successfully fitted based on a power law from the thermally activated magnetic flux creep model. From magneto-resistance measurements the temperature dependences of the transport critical currents and the irreversibility fields were found. The dc magnetic field dependence of the width of superconducting transitions and the critical currents was also obtained. These properties of the superconductors were analyzed within available theoretical models.

Magnetoresistance and Irreversibility Fields of Bismuth-Based 1G Tape

“…1a, b, respectively. At the zero field, the critical temperatures for this tape are as follows: T c50 % = 110.3 K and T c0 = 109.9 K, and the width of superconducting transition is T 0 = 0.5 K. One can notice a significant broadening of the superconducting transition with the application of the external magnetic field, which is typical for HTS [12,13]. Some authors link this phenomenon with the vortex structure and flux motion mechanism [14,15].…”

Study of Resistive Superconducting Transition of Bulk (Bi_{0.6}Pb_{0.4})_2Sr_2Ca_2Cu_{3}O_{x}

“…1. One can observe there a signicant widening of the transition in consequence of applying of the external magnetic eld, which is typical for HTS, especially for thallium based superconductors [2,3]. This phenomenon has been interpreted in the frame of the vortex structure and ux motion mechanism [4,5].…”

Electrical Conductivity and Magnetic Susceptibility of Thallium 1223-Based Superconductor in the Fluctuation Range

“…The diffraction spectrum was analyzed using FULLPROF software based on the Rietveld method [18]. Analysis of the XRD patterns showed that the sample contains two superconducting phases: the majority 1223 superconducting phase with the critical temperature T c,50% = 118.8 K as determined from resistance measurement and a minority 1212 superconducting phase that was not observed in either resistance or susceptibility measurements and which critical temperature reported in the papers [19,20] is of 100 K. The sample was found to contain also small amounts of non-conducting phases: CaCu 2 O 3 , CaO, SrBiO 3 , and Sr 8 Ca 6 Cu 24 O 41 .…”

“…Thus, following the paper [21,22], the dimensionality (d g ) of stochastic (Gaussian) fluctuations can be described as follows For the first region, the closest to the zero resistance critical temperature T c0 , we find that the value of critical exponent λ 1 is 0.23. Assuming that this region is dominated by critical fluctuations [19,20], using (7), we evaluated the dimensionality of the fluctuations in the first region at d c1 = 3.16. This result is in a good agreement with the assumption of 3D-XY universality class for our case.…”