Critical Current Decay in Josephson Junctions Containing Antiferromagnetic NiMn

Josephson junctions containing magnetic materials may be useful in superconducting electronics and memory. One design for a memory cell uses a junction containing an S/F/F'/S spin valve where the two ferromagnetic layers (F, F') have different switching fields. Such a spin valve can be made more robust if the hard layer is pinned by exchange bias with an adjacent antiferromagnetic (AF) layer. We report on the magnetic characterization of NiFe/NiMn and Ni/NiMn bilayer sheet films to confirm the pinning behavior of Ni₄₁Mn₅₉. We then report on the fabrication and measurement of S/N/AF/N/S Josephson junctions where NiMn is used as the AF layer, Nb as the S layer, and Cu as the N layer. From measurement of critical current in samples with NiMn thicknesses in the range from 1.2 nm to 6.0 nm, we measure the characteristic supercurrent decay length within NiMn to be 1.0 nm.