Visualizing supercurrents in ferromagnetic Josephson junctions with various arrangements of 0 and π segments

Gürlich, C., Scharinger, S., Weides, M. , Kohlstedt, H., Mints, R.G., Goldobin, E., Koelle, D. and Kleiner, R. (2010) Visualizing supercurrents in ferromagnetic Josephson junctions with various arrangements of 0 and π segments. Physical Review B, 81(9), 094502. (doi:10.1103/PhysRevB.81.094502)

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Abstract

Josephson junctions with ferromagnetic barrier can have positive or negative critical current depending on the thickness d F of the ferromagnetic layer. Accordingly, the Josephson phase in the ground state is equal to 0 (a conventional or 0 junction) or to π ( π junction). When 0 and π segments are joined to form a “ 0 − π junction,” spontaneous supercurrents around the 0 − π boundary can appear. Here we report on the visualization of supercurrents in superconductor-insulator-ferromagnet-superconductor (SIFS) junctions by low-temperature scanning electron microscopy (LTSEM). We discuss data for rectangular 0, π , 0 − π , 0 − π − 0 , and 20 × ( 0 − π − ) junctions, disk-shaped junctions where the 0 − π boundary forms a ring, and an annular junction with two 0 − π boundaries. Within each 0 or π segment the critical current density is fairly homogeneous, as indicated both by measurements of the magnetic field dependence of the critical current and by LTSEM. The π parts have critical current densities j π c up to 35   A / cm 2 at T = 4.2   K , which is a record value for SIFS junctions with a NiCu F-layer so far. We also demonstrate that SIFS technology is capable to produce Josephson devices with a unique topology of the 0 − π boundary.

Item Type:Articles
Status:Published
Refereed:Yes
Glasgow Author(s) Enlighten ID:Weides, Professor Martin
Authors: Gürlich, C., Scharinger, S., Weides, M., Kohlstedt, H., Mints, R.G., Goldobin, E., Koelle, D., and Kleiner, R.
College/School:College of Science and Engineering > School of Engineering > Electronics and Nanoscale Engineering
Journal Name:Physical Review B
Publisher:American Physical Society
ISSN:1098-0121
ISSN (Online):1550-235X
Published Online:03 March 2010

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