Anisotropic transport properties of ferromagnetic-superconducting bilayers

Abstract

We study the transport properties of vortex matter in a superconducting thin film separated by a thin insulator layer from a ferromagnetic layer. We assume an alternating stripe structure for both FM and superconducting (SC) layers as found in S. Erdin et al. [Phys. Rev. Lett. 88, 017001 (2002)]. We calculate the periodic pinning force in the stripe structure resulting from a highly inhomogeneous distribution of the vortices and antivortices. We show that the transport in SC-FM bilayer is highly anisotropic. In the absence of random pinning it displays a finite resistance for the current perpendicular to stripe and is superconducting for the current parallel to stripes. The average vortex velocity, electric field due to the vortex motion, Josephson frequency, and higher harmonics of the vortex oscillatory motion are calculated.