Attraction-repulsion transition between abrikosov vortices and Josephson vortices in the strongly layered superconductor Bi2Sr2CaCu2O8

A change in the effect of a frozen magnetic field parallel to the c-axis on rf power absorption, which is associated with the motion of Josephson vortices, is observed in the layered superconductor Bi₂Sr₂CaCu₂O₈ at a low temperature (～15 K). The effect is interpreted as a change in the interaction between an Abrikosov vortex and a Josephson vortex from attraction (at high temperatures) to repulsion (at low temperatures). It is found that the dynamics of the magnetic flux parallel to the ab plane of the single crystal becomes irreversible upon a transition of the superconductor to the layered state. Possible reasons behind the observed effect are considered, one of them being a manifestation of the second superconducting transition in the elementary-excitation spectrum of a d-type superconductor near the core of Abrikosov vortices.