Strongly anisotropic flux pinning in superconductingPb82Bi18 thin films covered by periodic ferromagnet stripes

Abstract

We have studied the vortex pinning via their magnetic interactionwith a periodic structure of parallel magnetic stripes. SuperconductingPb82Bi18 alloy films were covered by an insulating Ge layer and a periodic Ni array of magneticstripes was fabricated on the top of the Ge layer by electron-beam lithography and thermalevaporation. The critical current density was significantly stronger when the current wasapplied parallel to the stripes than when the current was perpendicular to the stripes.This is attributed to the barrier to the vortex motion provided by the magneticinteraction with the magnetic stripes. The enhancement in critical current was mostsignificant at temperatures close to the superconducting transition temperature.