Asymmetry, bistability, and vortex dynamics in a finite-geometry ferromagnet-superconductor bilayer structure

We have recently demonstrated that Py/Nb bilayers patterned in a strip geometry can exhibit asymmetric transport properties and bistability. Here, with the help of numerical simulations in the framework of time-dependent Ginzburg-Landau model for superconductor and Landau-Lifshitz-Gilbert model for ferromagnet, it is demonstrated that the asymmetric and bistable magnetotransport response of the bilayers can be accounted for by the stray fields from the patterned ferromagnetic layer. Numerical simulations on vortex dynamics show that in the dissipative branch of the bilayer a peculiar spontaneous channeled flux flow regime is realized, with alternating vortex and antivortex chains moving in the opposite directions in the superconducting layer.