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0-pi Josephson tunnel junctions with ferromagnetic barrier

M. Weides·M. Kemmler·E. Goldobin·H. Kohlstedt·R. Waser·D. Koelle·R. Kleiner
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Abstract

We fabricated high quality Nb/Al_2O_3/Ni_{0.6}Cu_{0.4}/Nb superconductor-insulator-ferromagnet-superconductor Josephson tunnel junctions. Using a ferromagnetic layer with a step-like thickness, we obtain a 0-pi junction, with equal lengths and critical currents of 0 and pi parts. The ground state of our 330 microns (1.3 lambda_J) long junction corresponds to a spontaneous vortex of supercurrent pinned at the 0-pi step and carrying ~6.7% of the magnetic flux quantum Phi_0. The dependence of the critical current on the applied magnetic field shows a clear minimum in the vicinity of zero field.

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M. Weides, M. Kemmler, E. Goldobin, H. Kohlstedt, R. Waser, D. Koelle, R. Kleiner. 2006-10-05. 0-pi Josephson tunnel junctions with ferromagnetic barrier. https://doi.org/10.1103/physrevlett.97.247001

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