Probing of high Tc sample texturing with a potentiometric ring

An inhomogeneously textured ring prepared from a diffused Bi2Sr2CaCu2O thick film has been arranged for the measurement of longitudinal, VL, and transverse, VT, voltages with three diametrical pairs of contacts. The film was deliberately grown in such a way that one half of the ring has a high degree of texturing with the a axis perpendicular to the sample plane. In the second, less textured half, a finer granular structure is present implying the presence of more grain boundaries. The application of an external magnetic field perpendicular and parallel to the sample plane clearly shows that an anisotropic weak link behavior from the inhomogeneous texturing is responsible for the minimum observed in VT below Tc. The reduction of this minimum with increasing magnetic field is explained in terms of the loss of superconducting paths due to increased dissipation at grain boundaries in the more textured branch.