Characterization of YBCO bicrystal grain-boundary Josephson junctions on ndgao3 substrate in terms of conventional superconductivity models

We have fabricated high quality grain-boundary
bicrystal YBCO Josephson junctions on the NdGaO3
substrates. At the temperature T=77 K,the I –V
characteristic can be explained by means of the
conventional overdamped resistively shunted junction
model comprising thermal noise.The deviations of the
magnetic dependence of the Josephson critical current
Ic from the usual Fraunhofer diffraction pattern can be
described by a combination of a peaked-at-the-edges
distribution of the critical current density and of the
rounding of the I –V characteristic due to thermal
fluctuations.The same measurements were done also at T
=4.2 K,at low thermal noise conditions.The experimental
magnetic field dependence Ic vs H was described by
using
a peaked-at-the-edges asymmetric profile,where the
asymmetry depends on the applied magnetic field.The
relation between our phenomenological model and
advanced microscopical theory of grain-boundary
bicrystal YBCO junction based on alternating 0 and PI-
contacts is discussed.2002