Chapter 7 Flux avalanches and magnetic asymmetry in Josephson arrays

Dependence of the magnetic moment of square arrays of Josephson junctions on a dc magnetic field and temperature has been studied experimentally. The arrays had junctions of SIS and SNS type. In SIS arrays, magnetic flux avalanches were observed at low temperatures. Statistical size distribution of magnetic avalanches is a power function with a crossover (the exponent changes from -0.7 for small sizes of avalanches to -6 for large sizes). The spectrum of avalanches at a linear development of the field is a power function of frequency. Such a behavior of avalanches is interpreted as a manifestation of the self-organized criticality. In SNS arrays, no avalanches are developed because of the high dissipation in junctions, but a considerable asymmetry of magnetic dynamics was found.[PUBLICATION ABSTRACT]