Meissner currents induced by topological magnetic textures in hybrid superconductor/ferromagnet structures

Topological spin configurations in proximity to a superconductor have recently attracted great interest due to the potential application of the former in spintronics and also as another platform for realizing nontrivial topological superconductors. Their application in these areas requires precise knowledge of the existing exchange fields and/or the stray fields, which are therefore essential for the study of these systems. Here, we determine the effective stray field Hstr and the Meissner currents jS in a superconductor/ferromagnet/superconductor (S/F/S) junction produced by various nonhomogenous magnetic textures M(r) in the F. The inhomogeneity arises either due to a periodic structure with flat domain walls (DW) or is caused by an isolated chiral magnetic skyrmion (Sk). We consider both Bloch- and Néel-type Sk and also analyze in detail the periodic structures of different types of DW's, that is, Bloch-type DW (BDW) and Néel-type DW (NDW) of finite width with in- and out-of-plane magnetization vector M(x). The spatial dependence of the fields Hstr(r) and Meissner currents jS(r) are shown to be qualitatively different for the case of Bloch- and Néel-type magnetic textures. While the spatial distributions in the upper and lower S are identical for Bloch-type Sk and DW's they are asymmetric for the case of Néel-type magnetic textures. The depairing factor, which determines the critical temperature Tc and which is related to the vector potential of the stray field, can have its maximum at the center of a magnetic domain but also, as we show, above the DW. For Sk's, the maximum is located at a finite distance within the Sk radius rSk. Based on this, we study the nucleation of superconductivity in the presence of DW's. Because of the asymmetry for Néel-type structures, the critical temperature Tc in the upper and lower S is expected to be different. The obtained results can also be applied to S/F bilayers.