Electromagnetic proximity effect in planar superconductor-ferromagnet structures

TL;DR

This paper reveals a long-range electromagnetic proximity effect in superconductor-ferromagnet structures, where magnetic fields transfer from ferromagnet to superconductor over large distances, impacting nanoscale device design.

Contribution

It introduces a novel inverse electromagnetic proximity effect driven by Cooper pair spread, with a characteristic length of the London penetration depth, distinct from previous spin polarization effects.

Findings

Long-range magnetic field transfer observed

Spontaneous currents generated without stray fields

Effect linked to vector potential near S/F interface

Abstract

The spread of the Cooper pairs into the ferromagnet in proximity coupled superconductor - ferromagnet (SF) structures is shown to cause a strong inverse electromagnetic phenomenon, namely, the long-range transfer of the magnetic field from the ferromagnet to the superconductor. Contrary to the previously investigated inverse proximity effect resulting from the spin polarization of superconducting surface layer, the characteristic length of the above inverse electrodynamic effect is of the order of the London penetration depth, which usually much larger than the superconducting coherence length. The corresponding spontaneous currents appear even in the absence of the stray field of the ferromagnet and are generated by the vector-potential of magnetization near the S/F interface and they should be taken into account at the design of the nanoscale S/F devices. Similarly to the well-known Aharonov-Bohm effect, the discussed phenomenon can be viewed as a manifestation of the role of vector potential in quantum physics.