Penetration of vortices into the ferromagnet/type-II superconductor bilayer

Abstract

Vortex structures in the ferromagnet/type-II superconductor bilayer are investigated when the ferromagnet has domain structure and perpendicular magnetic anisotropy. It is found that two equilibrium vortex structures can be realized: straight vortices with alternating directions corresponding to the direction of the magnetization in the ferromagnetic domains and vortex semiloops connecting the ferromagnetic domains with opposite direction of the magnetization. These states are separated by an energy barrier. The values of the critical magnetization for the formation of these vortex structures are determined.

Imaging the spontaneous formation of vortex-antivortex pairs in planar superconductor/ferromagnet hybrid structures

“…No spontaneous V-AV pairs were observed in zero applied magnetic field. It has been predicted theoretically that V-AV pairs could be induced by the outof-plane ferromagnet magnetization 19,20 when certain geometrical conditions between the ferromagnet stripe domain width, superconducting penetration depth and superconductor thickness are met. However, spontaneous V-AV pairs in planar S/F systems were not observed so far.…”

“…The condition for spontaneous formation of V-AV pairs in S/F hybrids has been considered theoretically in Ref. 19,20 in the case of a ferromagnet with out-of-plane magnetization forming alternating up and down domains ±M 0 along one of the in-plane axis. This simplified model is sufficient to describe the effect of the out-of-plane component of Py stray field on the vortices in the superconducting Nb film.…”

The Bean–Livingston barrier at a superconductor/magnet interface

“…Whilst for an ideal interface, with scale of roughness σ < ξ, vortex entry occurs at a distance a c ∼ = ξ, in the case of a real interface, with scale of roughness σ ≤ λ, vortex entry occurs for a c = σ. Equation (16) in conjunction with equation (15) thus yields for the critical field of first penetration of magnetic flux across the flat superconductor/magnet interface…”

Doppler-scanning tunneling microscopy current imaging in superconductor-ferromagnet hybrids

“…[19][20][21] The majority of experiments on planar magnetically coupled superconductor/ferromagnet heterostructures have so far been primarily focused on global measurements 13,[22][23][24][25] with theoretical insights based on London formalism. 26,27 However, the increased use of local probes, such as the scanning tunneling microscopy 28,29 and magnetic force microscopy (MFM), 30,31 has begun to reveal a rich body of new physics on the mesoscopic scale. In this work, we examine the local DOS in a thin lead film magnetically coupled to a Co-Pd multilayer.…”

“…For S/F systems which meet specific materials dependent and geometry dependent properties, it is possible to have Abrikosov vortices spontaneously generated in the superconducting film due to the stray fields of the underlying magnetic template even without applying external magnetic field. 26,31 In our system, the conditions for nucleation of spontaneous vortices are not fulfilled, so they are induced only when an external magnetic field is applied.…”