Fabrication of Optimized Superconducting Phase Inverters Based on Superconductor–Ferromagnet–Superconductor π-Junctions

• Published in: Journal of low temperature physics 2018, Vol.190 (5-6), p.302-314
• Main Authors: Bolginov, V. V., Rossolenko, A. N., Shkarin, A. B., Oboznov, V. A., Ryazanov, V. V.
• Format: Article
• Language: English
• Subjects: Characterization and Evaluation of Materials; Condensed Matter Physics; Critical current density; Diffusion barriers; Ferromagnetism; Interlayers; Inverters; Low temperature physics; Magnetic Materials; Magnetism; Physics; Physics and Astronomy; Superconductivity; Transition temperature
• ISSN: 0022-2291; 1573-7357
• DOI: 10.1007/s10909-017-1843-6

We have implemented a trilayer technological approach to fabricate Nb - Cu 0.47 Ni 0.53 - Nb superconducting phase inverters ( π -junctions) with enhanced critical current. Within this technique, all three layers of the superconductor–ferromagnet–superconductor junction deposited in a single vacuum cycle that have allowed us to obtain π -junctions with critical current density up to 20 kA/cm 2 . The value achieved is a factor of 10 higher than for the step-by-step method used in earlier works. Our additional experiments have shown that this difference is related to a bilayered CuNi/Cu barrier used in the case of the step-by-step technique and interlayer diffusion at the CuNi/Cu interface. We show that the interlayer diffusion can be utilized for fine tuning of the 0 - π transition temperature of already fabricated junctions. The results obtained open new opportunities for the CuNi-based phase inverters in digital and quantum Josephson electronics.