Angular dependence of the current-voltage characteristics and voltage fluctuation spectrum in ceramic superconductors

Measurements were made of the current-voltage characteristics and voltage f luctuation spectrum as functions of the angle between the magnetic field ap plied in the plane of the sample and the direction of the transport current in a YBa2Cu3O7-delta ceramic superconductor. The angular dependence of the fluctuation spectrum was measured first. It is shown that the current-volt age characteristics are not described using the vortex line cutting model a nd the voltage fluctuations are not caused by independent motion of vortice s in the bulk of the sample. The results are consistent with the model of a self-organized critical state. (C) 1999 American Institute of Physics. [S1 063-7850(99)00202-5].