Flux pinning in Bi-2212/Ag-based wires and coils

This paper describes a study of pinning forces in Ag/Bi-based wires and small coils. The goal of this analysis is to characterize and to compare the main pinning mechanisms in wires (short samples) and prototype practical devices, e.g., coils (long samples). The effects of thermal activation were found to hinder the straightforward determination of the pinning parameters from the critical current data. However, we succeeded in extracting these parameters from the irreversibility line. The scaling law for the pinning force employing the irreversibility field in virtue of the scale for magnetic fields was derived theoretically. The best fit to the experimentally determined pinning forces gave the flux-creep model corresponding to the power-law current—voltage dependence J∝Eⁿ. © 1996 The American Physical Society.