Magnetic dipole-vortex interaction in a bilayered superconductor/soft-magnet heterostructure

The penetration of the magnetic field of an infinitesimal magnetic dipole into a bilayered type-II superconductor/soft-magnet heterostructure is studied on the basis of the classical London approach. The energies associated with the presence of a straight magnetic vortex in the superconductor layer are derived and the critical dipole moment for the first vortex appearance is obtained when the magnetic dipole faces the superconductor or the soft-magnet constituent. This shows that the presence of the latter constituent can lead to an improvement of the superconducting properties of the heterostructure by either inhibiting vortex penetration into the superconductor constituent or enhancing vortex pinning in the superconductor constituent.