SELF-ORGANIZED CRITICALITY EFFECT ON STABILITY - MAGNETOTHERMAL OSCILLATIONS IN A GRANULAR YBCO SUPERCONDUCTOR

We show that the self-organized criticality of Bean's state in each of the grains of a granular superconductor results in magneto-thermal os cillations. We find that tile frequency of these oscillations is propo rtional to tile external magnetic field sweep rate B-e and is inversel y proportional to the square root of the heat capacity. We demonstrate experimentally and theoretically that this dependence is influenced m ainly by the granularity of the superconductor.