Electrically Switchable Ferromagnetic Josephson Junctions

Summary

This experimental project in superconducting spintronics will study spin-torques in ferromagnetic superconducting Josephson Junctions.

Superconducting computers operating at 4.2K have been proposed to solve the problems of energy usage by large-scale computing, as components for a neuromorphic computer and to interface between a quantum computer operator at millikelvin temperatures and conventional room temperature electronics. Whilst the technology to implement logic in such a 4.2K computer is well established, there remains, as yet, no suitable technology to implement cryogenic memory beyond registers. This project aims to address this need by developing the physics and materials to implement memory technologies based on ferromagnetic Josephson junctions.

A ferromagnetic Josephson junction based memory combines the magnetic storage capabilities of a conventional magneto-resistive RAM cell with the dissipation- less nature of a superconductors. As with the first generation of MRAM designs, our initial ferromagnetic Josephson junction designs rely on an applied field to set the state of the junction^1–3. In a modern MRAM cell, the state is set by making use of spin-transfer torque or spin-orbit torques to electrical change the magnetic state. To date, there has not been the equivalent step taken with the superconducting junction counterparts.

This project will suit a student with a strong background in condensed matter physics or materials physics and excellent experimental skills. A successful student will gain experience in thin film deposition techniques, micro and nanoscale device fabrication, low temperature measurements in addition to a deep knowledge of the rapidly growing field of superconducting spintronics.

1. Satchell, N. et al. Spin-valve Josephson junctions with perpendicular magnetic anisotropy for cryogenic memory. Appl. Phys. Lett. 116, 022601 (2020).

2. Bell, C., Burnell, G., Leung, C.-W., Tarte, E. J. & Blamire, M. G. Spin Valve Josephson Junctions. IEEE Trans. Appiled Supercond. 15, 908–911 (2005).

3. Baek, B., Rippard, W. H., Benz, S. P., Russek, S. E. & Dresselhaus, P. D. Hybrid superconducting-magnetic memory device using competing order parameters. Nat. Commun. 5, 3888 (2014).

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