Electromagnetic proximity effect and the Fulde–Ferrell–Larkin–Ovchinnikov instability in hybrid superconductor–ferromagnet structures (brief review)

Recent theoretical ideas concerning the mechanism of the electromagnetic proximity effect in hybrid superconducting structures with ferromagnetic layers, as well as the problem of Fulde–Ferrell–Larkin–Ovchinnikov (FFLO) instability with the modulation of the superconducting order parameter in the plane of the layers forming the structure, are reviewed. It is shown that, near the transition to the FFLO phase, the electromagnetic proximity effect can be enhanced: the corresponding spontaneous current flowing along the superconducting layer of the hybrid superconductor–ferromagnet structure increases drastically when approaching the FFLO transition line on the phase diagram of the structure. The transition to the FFLO phase can thus be observed using experimental techniques involving the diagnostics of the arising spontaneous currents.