Alternative mechanism of the sign-reversal effect in superconductor-ferromagnet-superconductor Josephson junctions

Abstract

We consider a simple model of a multidomain superconductor-ferromagnet-superconductor (SFS) Josephson junction. Sign-alternating magnetization $M$ in domains leads to a spatial modulation of the phase difference $\varphi (x)$. Due to this modulation the Josephson critical current $I_c$ may have a different sign depending on the ratio of the magnetic flux in a domain, 4$\pi Ma(2d_F),$ to the magnetic flux quantum. This phase modulation, but not a nonmonotonic dependence of the local critical current density $j_c$, may be the reason for oscillations of the current $I_c$ {\bf \}as a function of the F layer thickness $2d_F$ or temperature, observed in experiments.

6 pages, 2 figures. To be published in Phys.Rev. B