Josephson Junctions with a synthetic antiferromagnetic interlayer

TL;DR

This study investigates Nb/Cu/Co/Ru/Co/Cu/Nb Josephson junctions with a synthetic antiferromagnetic interlayer, revealing nearly zero net magnetic flux and stable Fraunhofer patterns, and explores their potential for spin-triplet superconductivity research.

Contribution

It provides experimental insights into the behavior of Josephson junctions with a synthetic antiferromagnetic interlayer, highlighting their magnetic and superconducting properties.

Findings

Excellent Fraunhofer patterns despite large Co thicknesses

No oscillations in critical current with Co thickness

Critical current decays over four orders of magnitude

Abstract

We report measurements of the critical current vs. Co thickness in Nb/Cu/Co/Ru/Co/Cu/Nb Josephson junctions, where the inner Co/Ru/Co trilayer is a "synthetic antiferromagnet" with the magnetizations of the two Co layers coupled antiparallel to each other via the 0.6 nm-thick Ru layer. Due to the antiparallel magnetization alignment, the net intrinsic magnetic flux in the junction is nearly zero, and such junctions exhibit excellent Fraunhofer patterns in the critical current vs. applied magnetic field, even with total Co thicknesses as large as 23 nm. There are no apparent oscillations in the critical current vs. Co thickness, consistent with theoretical expectations for this situation. The critical current of the junctions decays over 4 orders of magnitude as the total Co thickness increases from 3 to 23 nm. These junctions may serve as useful templates for future explorations of spin-triplet superconducting correlations, which are predicted to occur in supercon- ducting/ferromagnetic hybrid systems in the presence of certain types of magnetic inhomogeneity.