Hysteresis Losses in Bi-2223 Superconductors

In this study we examine magnetic hysteresis losses in Bi-2223 bulk superconductors. Two kinds of hysteresis losses were found in the samples: losses in superconducting grains and losses due to the intergranular weak link structure. Total losses at 77 K were about an order of magnitude higher than losses in grains. This indicates the domination of intergranular hysteresis losses with respect to intragrain losses.To understand the experimental results, we numerically simulated the behavior with model specimens, where different kinds of Josephson junction arrays worked as the models for the intergrain system. A special attention was paid to the influence of porosity, second phase particles, and magnetically induced granularity on the hysteresis losses. If at least one of the inhomogeneity sources was present, the magnetization of the array could exhibit remarkable hysteresis and losses.