Proximity and Josephson effects in superconductor/antiferromagneticNb/γ−Fe50Mn50heterostructures

We study the proximity effect in superconductor (S), antiferromagnetic (AF)\nbilayers, and report the fabrication and measurement of the first trilayer\nS/AF/S Josephson junctions. The disordered f.c.c. alloy \\gamma-Fe50Mn50 was\nused as the AF, and the S is Nb. Micron and sub-micron scale junctions were\nmeasured, and the scaling of $J_C (d_AF)$ gives a coherence length in the AF of\n2.4 nm, which correlates with the coherence length due to suppression of $T_C$\nin the bilayer samples. The diffusion constant for FeMn was found to be 1.7\n\\times 10$^{-4}$ m$^2$ s$^-1$, and the density of states at the Fermi level was\nalso obtained. An exchange biased FeMn/Co bilayer confirms the AF nature of the\nFeMn in this thickness regime.\n