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

Measurements were made of the current-voltage characteristics and voltage fluctuation spectrum as functions of the angle between the magnetic field applied in the plane of the sample and the direction of the transport current in a YBa₂Cu₃O_7−δ ceramic superconductor. The angular dependence of the fluctuation spectrum was measured first. It is shown that the current-voltage characteristics are not described using the vortex line cutting model and the voltage fluctuations are not caused by independent motion of vortices in the bulk of the sample. The results are consistent with the model of a self-organized critical state. Pis’ma Zh. Tekh. Fiz. 25, 8–13 (February 12, 1999)