ИСТИНА

It is well known that strong anisotropy of resistivity of high-Tc materials should be be taken into account during interpretations of electrical data. The same is true for grain boundary junctions (GB), since superconducting electrodes are anisotropic materials. Therefore, simply considering these GB junctions as structures biased by homogeneously distributed current may result in incorrect interpretations. In the re- port we demonstrate that even in a nanowire composed from two single-crystalline high-Tc thin films separated by [100] tilt GB, an assumption of a uniform distribution of the normal current over the film thickness generally does not work and is valid only in the limit of extremely small conductivity of GB interface. We developed the self-consistent method for the calculation of the current distribution in bicrystal grain boundary (GB) junctions. We demonstrate that anisotropy of its distribution inside the single crystal grains results in effects, which previously was not taken into ac- count for the data interpretations. They are significant redistribution of current over the thickness of the superconductor in the vicinity of the grain boundary, which may be accompanied by its substantial focusing on the top or bottom part of interface, and a generation of vortex currents around grain boundary resulting in selfbiasing of GB junctions by the magnetic field nucleated by these vortex currents. It is shown that twinning or a change of geometrical shape of GB electrode may also leads to inten- sive redistribution of a current and nucleation of local magnetic fields inside a single grain. This work has been supported by RFBR project 11-07-12023-ofi-m-2011 and, in part by Swedish Institute Visby Grant 00910=2011.