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Abstract: This work reports the influence of the granularity on the transverse voltage as a function of the temperature, V XY (T), in polycrystalline samples of Bi2Sr2Ca0.8Pr0.2Cu2O8+δ composition. It is observed nonzero transverse voltage at zero external magnetic field in the vicinity of the superconducting transition while far away from it, both above and below, no such voltage was detected. Measurements of V XY (T) in both directions of magnetic field allowed to calculate the symmetric and asymmetric transverse voltages in the full range of the applied magnetic field studied (zero up to 9T). The symmetric transverse voltage as a function of the temperature presents sign reversal of the Hall resistance and positive Hall voltage at normal state such as expected for hole-doped high critical temperature superconductors. On the other hand, the asymmetric component of V XY (T) shows a peak near the superconducting transition which has been recently reported in literature. V XY (T) curves measured in a sample with double superconducting transition, which was confirmed by ac-susceptibility measurements and hysteresis loops of the magneto-resistance, present two peaks in the asymmetric component. These peaks are related to the intergranular and intragranular transitions and can be explained within the framework of Josephson and Abrikosov vortices and anti-vortices motion. By comparing the temperature dependence of the asymmetric transverse voltage and the derivative of longitudinal voltage is possible to observe a specific relation between both transport properties, which is noted to be valid not only at zero applied magnetic field but also under applied field. [Copyright &y& Elsevier]

In order to study Hall effect in Y0.55Pr0.45Ba2Cu3O7-δ polycrystalline samples we have measured longitudinal and transverse voltages at low magnetic field using Van der Pauw technique. The results of the Hall resistance RXY as a function of temperature presented double sign reversal which crosses to the positive sign at same temperature in which branching point (TCj) of the electrical resistance RXX occurs. Magneto-resistance hysteresis loops demonstrated that the dissipation is dominated by weak coupling between superconducting clusters. The results suggest that the positive Hall voltage at superconducting state is due to quasiparticle current which is in good agreement with the recent discussion about the applying of the resistively shunted junction model to polycrystalline samples. [Copyright &y& Elsevier]

This work presents results about the influence of the applied magnetic field on the branching point of the resistive transition in granular samples of the Y1-xPrxBa2Cu3O7-δ (Y123 + Pr) system. Single phase samples of x=0.0 and 0.35 composition were prepared by solid state reaction method. Using several resistance curves as a function of the temperature measured at different applied currents we defined branching points at each magnetic field which was ranged from 0 up to 9 T. We have observed that a line in the H–T phase diagram separates the weak coupling state from decoupled regime of the superconducting clusters. Measurements of current–voltage curves and magneto-resistance hysteresis loops agree with such discussion. [Copyright &y& Elsevier]

Abstract: This work reports a systematic study on the structural and superconducting properties in the Hg–Sm–In–Pb system. It is investigated how In and Sm dopings influence the superconducting properties of the HgPb2 phase which was recently reported. Results for the HgSm1− x Pb2 system show that Sm atoms substitute Hg vacancies in the tetragonal phase which do not affect the onset critical temperature of the HgPb2 compound. Simultaneous Sm and In doping effects on the properties of the HgPb2 phase are also studied. Experimental and simulations of X-ray powder diffractograms suggest that the HgSm1− x In x Pb2 system (0.2≤ x ≤0.7) has a pseudo-cubic structure with lattice parameters near 4.88 Å. Superconducting properties measurements show that this system has an optimum doping at x ∼0.5 with the onset critical temperature close to 6.9 K. This is the highest superconducting critical temperature for the AuCu prototype so far reported. [Copyright &y& Elsevier]

In this work, we have studied the superconductivity in the Hg–Pb system. The results show that the HgPb2 is an intermetallic phase which presents superconductivity with critical temperature strongly dependent on the Pb content. This phase crystallizes in the prototype AuCu structure with tetragonal symmetry and solubility limit between 65 and 73 at.% of lead content on compound. The critical temperature and the a lattice parameter change linearly with lead content within the solubility limit of the HgPb2 phase . In the full limit, critical temperature varies from 5.6 to 6.0 K. Results of resistance measurement as a function of the temperature, X-ray diffractometry, microstructural analysis and magnetization measurements are presented. The results indicate that the critical temperature of 6.0 K of the sample doped with 73 at.% of Pb is the highest Tc reported up to now for the prototype AuCu structure. [Copyright &y& Elsevier]