Coupling of two superconductors through a ferromagnet: evidence for a pi junction
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Published on: August 2, 2019
V V Ryazanov1, V A Oboznov, A Y Rusanov
1Institute of Solid State Physics, Russian Academy of Sciences, Chernogolovka.
Abstract:
We report measurements of the temperature dependence of the critical current, I(c), in Josephson junctions consisting of conventional superconducting banks of Nb and a weakly ferromagnetic interlayer of a CuxNi1-x alloy, with x around 0.5. With decreasing temperature I(c) generally increases, but for specific thicknesses of the ferromagnetic interlayer, a maximum is found followed by a strong decrease down to zero, after which I(c) rises again. Such a sharp cusp can be explained only by assuming that the junction changes from a 0-phase state at high temperatures to a pi phase state at low temperatures.
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