Josephson Junctions with a synthetic antiferromagnetic interlayer

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.Comment: 4 pages, 5 figure

Spin-memory loss at Co/Ru interfaces

We have determined the spin-memory-loss parameter, $\delta_{Co/Ru}$, by measuring the transmission of spin-triplet and spin-singlet Cooper pairs across Co/Ru interfaces in Josephson junctions and by Current-Perpendicular-to-Plane Giant Magnetoresistance (CPP-GMR) techniques. The probability of spin-memory loss at the Co/Ru interface is $(1-exp(-\delta_{Co/Ru}))$. From the CPP-MR, we obtain $\delta_{Co/Ru} = 0.34^{+0.04}_{-0.02}$ that is in good agreement with $\delta_{Co/Ru} = 0.35 \pm 0.08$ obtained from spin-triplet transmission. For spin-singlet transmission, we have $\delta_{Co/Ru} = 0.64 \pm 0.05$ that is different from that obtained from CPP-GMR and spin-triplet transmission. The source of this difference is not understood.Comment: 9 pages, 9 figure