Optimizing supercurrent transmission and magnetic behavior in ferromagnetic Josephson junctions

Josephson junctions with ferromagnetic layers where the ground-state phase difference can be reliably controlled are a potential candidate for applications in cryogenic memory devices, which can greatly reduce the ever-growing energy requirements for large-scale computing. Phase control has been successfully demonstrated with junctions containing a Ni fixed layer and a NiFe free layer[1,2]. However, there are still a number of improvements that can be made to increase the efficiency and reliability of these junctions. We present work on trying to improve the efficiency by using thin layers of Ni “dusting” around the NiFe free layer to further increase the transmission of supercurrent through these junctions. We also present work on improving the switching reliability by replacing the fixed Ni layer with unbalanced Ni SAFs which may have more desirable magnetic properties.

[1] E. C. Gingrich, B. M. Niedzielski, J. A. Glick, Y. Wang, D. L. Miller, R. Loloee, W. P. Pratt, and N. O. Birge, Nat. Phys. 12, 564 (2016).
[2] I. Dayton, T. Sage, E. Gingrich, M. Loving, T. Ambrose, N. Siwak, S. Keebaugh, C. Kirby, D. Miller, A. Herr, Q. Herr, and O. Naaman, IEEE Magn. Lett. 9, 3301905 (2018).