Formation of the central peak in magnetization loops of type-II superconductors

Abstract

Based on magneto-optical observations of flux distributions on high-Tc single crystals and thin films aroundB=0 T at various temperatures, possible origins for the formation of the central peak commonly found in magnetization loops of hard type-II superconductors are discussed. The appearence of the central peak is closely related to the the full-penetration field,H*. It is shown that a reduction of the sample thickness influences the value ofH*, thus leading to a narrower field range for the rearrangement of the vortices when passingB=0 T. The role of pinning in the formation of the central peak and the role of the central peak in the formation of the fishtail effect is also discussed.