Josephson tunnel junctions with the strong ferromagnetic alloy \Fe0.75\Co0.25 as the barrier material were studied. The junctions were prepared with high quality down to a thickness range of a few monolayers of Fe-Co. An oscillation length of ξF2≈0.79nm between 0 and π-Josephson phase coupling and a very short decay length ξF1≈0.22nm for the amplitude of the superconducting pair wave function in the Fe-Co layer were determined. The rapid damping of the pair wave function inside the Fe-Co layer is caused by the strong ferromagnetic exchange field and additional magnetic pair breaking scattering. Josephson junctions with Fe-Co barriers show a significantly increased tendency towards magnetic remanence and flux trapping for larger thicknesses dF.
@article{arxiv.0905.0761,
title = {Josephson tunnel junctions with ferromagnetic $\Fe_{0.75}\Co_{0.25}$ barriers},
author = {D. Sprungmann and K. Westerholt and H. Zabel and M. Weides and H. Kohlstedt},
journal= {arXiv preprint arXiv:0905.0761},
year = {2009}
}