Magnetic pinning in superconductor-ferromagnet multilayers

Abstract

We argue that superconductor/ferromagnet multilayers of nanoscale period should exhibit strong pinning of vortices by the magnetic domain structure in magnetic fields below the coercive field when ferromagnetic layers exhibit strong perpendicular magnetic anisotropy. The estimated maximum magnetic pinning energy for single vortex in such a system is about 100 times larger than the pinning energy by columnar defects. This pinning energy may provide critical currents as high as 106−107 A/cm2 at high temperatures (but not very close to Tc) at least in magnetic fields below 0.1 T.