Structural Image of the Barrier of YBa2Cu3O7 Grain Boundary Josephson Junctions Based on the Analysis of the Electromagnetic Parameters

In general, information about the structure of the barrier in YBa2Cu3O7 (YBCO) grain boundaries Josephson junctions ( GBJJs) has been mainly derived by means of destructive techniques. In this line, any structural data directly derived from the analysis of the electromagnetic and transport parameters would be very useful. For GBJJs based on three bicrystalline geometries (24 degrees [001] asymmetric, 45 degrees [100] asymmetric and 24 degrees [001] symmetric + 45 degrees [100] asymmetric) we present a structural study of the barrier based on the transport and electromagnetic parameters deduced from the current-voltage ( I-V) curves. The dependence of the critical current (I-C) on the junction resistance (R-N) shows an approximately ICRN-1 power law type dependence. This result is in accordance with a SNINS or SIS description of the barrier. Concerning the electromagnetic parameters, we have calculated the capacitance ( C) by means of Fiske resonance positions and hysteresis observed in the I-V curves. While C values calculated with both methods are similar in the case of YBCO 24 degrees [ 001] asymmetric GBJJs, the ones deduced from Fiske resonances are always higher in the case of the other two misorientation angles, where a [ 100] component is present. This discrepancy allows us to estimate the length of the normal N regions at both sides of the barrier.