We report on transport properties of grain boundaries fabricated in YBa2Cu3O7-x thin films grown by the liquid phase epitaxy (LPE) technique on MgO asymmetrical bicrystal substrate with 45o misorientation angle. In total around 10 samples have been s
tudied. Substantial scatter of zero field values of the critical current density at 5K has been observed. The upper limit of Jc of the order of 104 A/cm2 found in our study is close to previously reported data for 45o bicrystals grown by various physical vapour deposition methods while the minimal value of Jc for the LPE grown bicrystals in striking difference to the results published before is exactly equal to zero. For samples with non-zero Jc we have found a few different types of critical current dependence on magnetic field ranging from pattern reminiscent Fraunhover-like Ic(H) to Ic(H) profile with Ic minimum at zero field.
We have studied electrical transport properties of a high quality Bi2Sr2Ca2Cu3O10+x crystal below a superconducting critical temperature, Tc. In magnetic fields B parallel to the c-axis just above a voltage response onset resistance vs temperature da
ta are well fitted to the vortex-glass model. Obtained from the vortex-glass analysis a melting transition boundary for Bi-2223 crystal shifted towards lower temperatures compared to previously reported data for a (Bi,Pb)-2223 single crystal. The critical current density, Jc, of Bi-2223 crystals is close to presented elsewhere Jc values for Bi-2223 tapes suggesting a principal role of weak intrinsic pinning properties of Bi-2223 as a main limiting factor of Jc of Bi-2223 conductors.
We report on study of the vortex liquid in Pb-doped Bi-2223 single crystal using the in-plane resistivity measurements as a function of temperature and magnetic field up to 6T applied perpendicular to CuO planes. Below Tc at the upper part of superco
nducting transition we found Arrhenius-like resistivity behavior. With further temperature decrease close to resistivity onset resistivity shows power law dependence on temperature signaling approaching vortex-glass transition. The critical exponents nu(z-1)=4.6 plus-minus 0.5 are found to be field independent within experimental errors. We also present magnetic phase diagram defining region of nonzero critical current for Pb-doped Bi-2223 single crystal.
