Anomalous position of the maximum in magnetic hysteresis loops measured on (Bi,Pb)2Sr2Ca2Cu3O10/Ag tapes

An anomalous position of the central peak of magnetic hysteresis loops is observed in (Bi,Pb)-2223/Ag tapes at positive external fields Bext for dBext/dt<0. We model the grain structure by a system of superconducting disk-shaped grains touching each other in small, but highly conducting contacts at the disk circumferences. The sign of the internal field Bi at the circumference of large, thin well oriented grains in the tape plays an important role. While in great majority of the sample volume Bi is delayed behind Bext, just at the grain circumferences Bi might be considerably ahead of Bext. Based on these considerations, a model sample which should exhibit similar features of the central peak is proposed.