Characteristics of strong ferromagnetic Josephson junctions with epitaxial barriers.pdfVIP

Characteristics of strong ferromagnetic Josephson junctions with epitaxial barriers C. Bell∗ Materials Science Department, IRC in Superconductivity and IRC in Nanotechnology, University of Cambridge, Cambridge, UK 5 R. Loloee 0 Department of Physics and Astronomy, Center for Sensor Materials and Center for Fundamental Material Research, 0 Michigan State University, East Lansing, Michigan 48824, USA 2 b G. Burnell, M. G. Blamire e Materials Science Department, IRC in Superconductivity and IRC in Nanotechnology, University of Cambridge, Cambridge UK F (Dated: February 2, 2008) 2 We present the measurement of superconductor / ferromagnetic Josephson junctions, based on 2 an epitaxial Nb bottom electrode and epitaxial Fe20Ni80 barrier. Uniform junctions have been fabricated with a barrier thicknesses in the range 2 − 12 nm. The maximum critical current density ] ∼ 2.4 ± 0.2 × 109 Am−2 was found for a devices with a 3 nm thick barrier at 4.2 K, corresponding n o to an average characteristic voltage IC RN ∼ 16 µV. The IC RN showed a non-monotonic behavior c with Fe20Ni80 thickness. The variation of the resistance of a unit area ARN , of the junctions with - barrier thickness gave a Nb/Py specific interface resistance of 6.0 ± 0.5 fΩm2 and Fe20Ni80 resistivity r of 174 ± 50 nΩm, consistent with other studies in polycrystalline samples. p u s PACS