Controllable 0 – π Switching in Ferromagnetic Josephson Junctions for Cryogenic Memory*

Josephson junctions containing ferromagnetic layers have generated recent interest for application in cryogenic memory. In a junction containing a magnetically hard fixed layer and soft free layer with specific thicknesses the phase state can be switched between zero and π by changing the relative magnetization of the two layers from antiparallel to parallel [1]. This phase switching has been observed in junctions with Ni fixed layers and NiFe free layers [2]. We present phase-sensitive measurements of such junctions in low-inductance symmetric SQUID loops, which simplify analysis relative to our previous work. We observe controllable switching in multiple junctions with Ni fixed layers of thickness 1.6nm and 2.0nm to begin mapping a phase diagram of zero and π states vs. Ni and NiFe thicknesses.


[1] B. M. Niedzielski, et al., arXiv:1709.04815 (2017)
[2] E. C. Gingrich, et al., Nature Phys. 12, 564–567 (2016)