Vortex lattice dynamics multilayers

We have investigated vortex dynamics in (Formula presented)(Formula presented)(Formula presented)/((Formula presented)(Formula presented))(Formula presented) multilayers in parallel and perpendicular applied magnetic fields. In both configurations, we have measured activation energies U for flux motion and determined vortex coupling through either ferromagnetic ((Formula presented)) or nonmagnetic ((Formula presented)) barriers. Coupled motion of pancake vortices belonging to different (Formula presented)(Formula presented)(Formula presented) layers occurs for nonmagnetic barriers ((Formula presented)) as large as several hundreds of Å . In the case of ferromagnetic barriers ((Formula presented)), 50 Å was found to be sufficient to decouple the vortices between the barrier. The ferromagnetism present in the (Formula presented) barrier is believed to be responsible for such behavior. © 1996 The American Physical Society.