Phase dependence of the Josephson current in inhomogeneous high-Tc grain-boundary junctions

We present an experimental and theoretical study of the current-phase relation I-s(phi) for 45 degrees grain boundaries in YBa2Cu3O7-x films. A model of strongly inhomogeneous Josephson junctions, in which the presence of randomly alternating current leads to a deviation of I-s(phi) from the well-known sin(phi) dependence, has been used. This deviation decreases with the temperature T and is described by the formula I-s(phi) = I-c(T)(sin phi + gamma(T)sin2 phi). Using the developed model, the coefficient gamma is calculated and its temperature dependence is found to be in good agreement with experiment. [S0163-1829(99)01417-4].