Probing the magnetic screening properties of superconductor-ferromagnet hybrids.*

Ferromagnetic Josephson junctions are a strong candidate for a dissipationless cryogenic memory alternative to dissipative CMOS technologies. Much attention has been focused on what happens to the supercurrent propagating through the Josephson junction, including the discovery of spin aligned triplet Cooper pairs in these systems [1]. In parallel, the magnetic screening properties of superconductors in electronic proximity to ferromagnetic materials have been studied, as an additional component of the screening is expected to be induced by the proximity effect [2]. These additional screening currents may account for several experimental observations, most notably in Co/Nb/Cu trilayers where an anomalous Meissner effect is reported by the low energy muon spin rotation technique [3]. In this work, we report our progress characterising the magnetic screening properties of isolated Nb (200 nm) and a bilayer of Ni (x nm)/Nb (200 nm) using polarized neutron reflectometry and the Fraunhofer characteristic of Josephson junctions.

[1] Norman O. Birge, Phil. Trans. R. Soc. A 376, 20150150 (2018)
[2] S. Mironov et al., Appl. Phys. Lett. 113, 022601 (2018)
[3] M. G. Flokstra et al., Phys. Rev. Lett. 120, 247001 (2018)