Ac susceptibility of a coated conductor with high-temperature superconducting film and covered copper stabilizer

Abstract

The ac susceptibility, χ=χ′-jχ″, of a nearly square sample, cut from a coated conductor tape consisting of a high-temperature superconducting film and a covered copper stabilizer, is measured as a function of temperature, T, at several values of frequency, f. It is found that the χ(f) at T>Tc can be well simulated by a modeling eddy-current susceptibility of the stabilizer, and there is an extra low-T stage, where χ is not constant as expected and may be separated into two parts. The T-independent part is contributed by Meissner currents in the film with over-low |χ′|, indicating that the film edge was damaged by cutting during tape and sample preparation. The T-dependent part is contributed by both eddy-currents and supercurrents, having a special f dependence with unknown mechanism. Both currents are interacted to each other in a complex way in the T range below and near Tc, resulting in interesting features in χ(T,f).