Electromagnetic proximity effect in superconductor/ferromagnet bilayers with in-plane magnetic texture

Abstract

The so-called electromagnetic proximity effect manifests itself as the long-range leakage of the magnetic field from a ferromagnet (F) to a superconductor (S), which is in electrical contact with the ferromagnet. In the present paper, we study the proximity-induced supercurrent and magnetic field in S/F bilayer systems with an in-plane inhomogeneous ferromagnet. We find that at the S/F interface a spontaneous surface current appears which is perpendicular to the local in-plane magnetization. In this sense, S/F bilayers with a metallic ferromagnet mimic similar systems with an insulating ferromagnet, where a surface current appears due to the interplay of the exchange field and Rashba spin-orbit coupling. We consider three geometrical configurations of the ferromagnet: a uniformly magnetized strip, an infinite slab with two domains and a Néel wall between them, and a ferromagnetic disk with a magnetization vortex. It is found that the proximity effect in the magnetic strip geometry induces a magnetic field outside the ferromagnet (which vanishes in the absence of proximity coupling between S and F), and in the other two geometries it enhances the magnetic field far from the domain wall or the core of the magnetic vortex. Possible experimental methods to probe the described features are discussed.