On the extended elliptic critical-state model for hard superconductors

The magnetic behavior of an irreversible type-II superconducting slab under the action of in-plane crossed fields is investigated within both the original elliptic critical-state model and the extended one, which was recently proposed by Clem. In particular, we study the suppression of the remanent magnetization of a PbBi specimen by a sweeping external transverse magnetic field. It is found that both elliptic critical-state models reproduce the main features of available experimental magnetization curves. We also show that the average magnetizations, corresponding to diamagnetic and paramagnetic initial states at a static bias field H-z, are asymmetrically reduced by the action of an oscillating transverse field H-y. If the amplitude of the oscillations of H-y is as large as the first penetration field HP, the resulting state becomes paramagnetic after various cycles of H-y. Such a kind of paramagnetism is attributed to the anisotropy, induced by flux-line cutting effects, in the critical current density. In PbBi samples, paramagnetism is expected to be manifest in a wide range of values of the static bias field H-z.