Large critical current density Josephson $π$ junctions with PdNi barriers

Arjun Sapkota; Pukar Sedai; Robert M. Klaes; Reza Loloee; Norman O. Birge; Nathan Satchell

doi:10.1063/5.0317028

paper

Large critical current density Josephson $π$ junctions with PdNi barriers

arXiv:2505.03913 · doi:10.1063/5.0317028

Abstract

We report large $π$ -state critical current densities, $J_{c} (π)$ , in Nb/Pd $_{89}$ Ni $_{11}$ /Nb Josephson junctions at Pd $_{89}$ Ni $_{11}$ thicknesses near the first $π$ -state. We observe oscillations in the critical current with ferromagnetic barrier thickness consistent with a $0$ - $π$ transition. For a junction with a 9.4~nm Pd $_{89}$ Ni $_{11}$ barrier, we obtain $J_{c} (π) = 410 kA/c m^{2}$ at 4.2~K, exceeding values reported in prior PdNi-based studies. Magnetization measurements on continuous films, together with coercivity tests on patterned arrays, confirm that Pd $_{89}$ Ni $_{11}$ exhibits perpendicular magnetic anisotropy, enabling zero-field operation without magnetic initialization. The combination of large $J_{c} (π)$ and intrinsic anisotropy establishes Pd $_{89}$ Ni $_{11}$ as a promising barrier material for passive $π$ -shifters in superconducting digital logic and qubit architectures.

arXiv comment7 pages, 5 figures

Large critical current density Josephson π junctions with PdNi barriers

Abstract

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Large critical current density Josephson $π$ junctions with PdNi barriers