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Planar SFS Josephson Junctions Made by Focused Ion Beam Etching

V. M. Krasnov·O. Ericsson·S. Intiso·P. Delsing·V. A. Oboznov·A. S. Prokofiev·V. V. Ryazanov
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Abstract

Superconductor-Ferromagnet-Superconductor (S-F-S) Josephson junctions were fabricated by making a narrow cut through a S-F double layer using direct writing by Focused Ion Beam (FIB). Due to a high resolution (spot size smaller than 10 nm) of FIB, junctions with a small separation between superconducting electrodes ($\leq$ 30 nm) can be made. Such a short distance is sufficient for achieving a considerable proximity coupling through a diluted CuNi ferromagnet. We have successfully fabricated and studied S-F-S (Nb-CuNi-Nb) and S-S'-S (Nb-Nb/CuNi-Nb) junctions. Junctions exhibit clear Fraunhofer modulation of the critical current as a function of magnetic field, indicating good uniformity of the cut. By changing the depth of the cut, junctions with the $I_c R_n$ product ranging from 0.5 mV to $\sim 1μ$V were fabricated.

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V. M. Krasnov, O. Ericsson, S. Intiso, P. Delsing, V. A. Oboznov, A. S. Prokofiev, V. V. Ryazanov. 2004-11-05. Planar SFS Josephson Junctions Made by Focused Ion Beam Etching. https://doi.org/10.1016/j.physc.2004.11.004

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