The present work aims to explain the anomalous position of the low-field peak in magnetization loops in Bi-2223 tapes, where the peak is often seen shifted to a positive field on the descending field branch. We prove theoretically that for an infinitely thin and long strip placed in a perpendicular field, the central peak occurs exactly at 0 T, for any function Jc(B). This general result is shown to be in excellent agreement with experimental data. After introducing granularity in such a film into a lattice of small weakly-overlapping disks, the peak becomes shifted to positive values. We conclude that this anomalous behaviour in the magnetization is a definite signature of granularity.
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