Proximity and Josephson effects in superconductor/antiferromagnetic Nb/gamma-Fe50Mn50 heterostructures

We study the proximity effect in superconductor (S), antiferromagnetic (AF) bilayers, and report the fabrication and measurement of the first trilayer S/AF/S Josephson junctions. The disordered fcc alloy gamma-Fe50Mn50 was used as the AF, and the S is Nb. Micron and submicron scale junctions were measured, and the scaling of J(C)(d(AF)) gives a coherence length in the AF of 2.4 nm, which correlates with the coherence length due to suppression of T-C in the bilayer samples. The diffusion constant for FeMn was found to be 1.7x10(-4) m(2) s(-1), and the density of states at the Fermi level was also obtained. An exchange biased FeMn/Co bilayer confirms the AF nature of the FeMn in this thickness regime.