Interaction of Josephson and Abrikosov vortices in a Y-Ba-Cu-O superconductor

The penetration of weak magnetic fields (0-n × 10⁻² T) into a Y-Ba-Cu-O ceramic supercon-ductor is studied. The nucleation fields for Abrikosov and Josephson vortices (fluxons) and the boundaries of the range in which the amplitude of the high-temperature superconductor response depends on the superposition of the dc field and weak variable fields caused by the fluxon mobility are experimentally determined.