Critical current density behaviors across a grain boundary inclined to current with different angles in YBa2Cu3O7−δ bicrystal junctions**Project supported by the National Natural Science Foundation of China (Grant Nos. 61501222, 61371036, and 61571219) and the School Scientific Research Fund of Nanjing Institute of Technology, China (Grant Nos. YKJ201418).

Abstract

The critical current density behaviors across a bicrystal grain boundary (GB) inclined to the current direction with different angles in YBa2Cu3O7−δ bicrystal junctions in magnetic fields are investigated. There are two main reasons for the difference in critical current density in junctions at different GB inclined angles in the same magnetic field: (i) the GB plane area determines the current carrying cross section; (ii) the vortex motion dynamics at the GB affects the critical current value when the vortex starts to move along the GB by Lorentz force. Furthermore, the vortex motion in a bicrystal GB is studied by investigating transverse (Hall) and longitudinal current–voltage characteristics (I–Vxx and I–Vxy). It is found that the I–Vxx curve diverges from linearity at a high driving current, while the I–Vxy curve keeps nearly linear, which indicates the vortices inside the GB break out of the GB by Lorentz force.