Abstract
We present a quantitative study of the current–voltage characteristics (CVC) of SFIFS Josephson junctions (S = bulk superconductor, F = metallic ferromagnet, I = insulating barrier) with weak ferromagnetic interlayers in the diffusive limit. The problem is solved in the framework of the nonlinear Usadel equations. We consider the case of a strong tunnel barrier such that the left SF and the right FS bilayers are decoupled. We calculate the density of states (DOS) in SF bilayers using a self-consistent numerical method. Then we obtain the CVC of corresponding SFIFS junctions, and discuss their properties for different set of parameters including the thicknesses of ferromagnetic layers, the exchange field, and the magnetic scattering time. We observe an anomalous nonmonotonic CVC in case of weak ferromagnetic interlayers, which we attribute to DOS energy dependencies in the case of small exchange fields in the F layers.
Highlights
It is well known that superconductivity and ferromagnetism are two competing antagonistic orders
We present the results of the density of states (DOS) energy dependencies in SF bilayers at the free boundary of the F layer for h ≤ Δ
We note that the DOS at the end of an SF bilayer in case of a domain wall in the ferromagnetic layer was studied in [104]
Summary
It is well known that superconductivity and ferromagnetism are two competing antagonistic orders. At small exchange fields the decay length of superconducting correlations in the ferromagnetic material, ξh, is large enough, which leads to profound variations of the superconducting density of states in the F layer as a function of the energy and results in a corresponding CVC behavior. In case of weak ferromagnetic metals we find an anomalous nonmonotonic shape of the current–voltage characteristics at subgap voltages and compare the results with the CVC of SIFS junctions [45].
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