Vortex lattice dynamics in DyBa2Cu3O7/(Sr1-xCax)RuO3 multilayers

We have investigated vortex dynamics in DyBa2Cu3O7/(Sr1-xCax)RuO3 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 (SrRuO3) or nonmagnetic (CaRuO3) barriers. Coupled motion of pancake vortices belonging to different DyBa2Cu3O7 layers occurs for nonmagnetic barriers (CaRuO3) as large as several hundreds of Angstrom. In the case of ferromagnetic barriers (SrRuO3), 50 Angstrom was found to be sufficient to decouple the vortices between the barrier. The ferromagnetism present in the SrRuO3 barrier is believed to be responsible for such behavior.