Electrically-controlled hybrid superconductor-ferromagnet cell for high density cryogenic memory

TL;DR

This paper presents a novel hybrid superconductor-ferromagnet device operating at cryogenic temperatures, enabling electrically-controlled magnetic states for high-density cryogenic memory applications.

Contribution

It introduces a new SISFS Josephson junction design with electric control of magnetization for cryogenic memory, combining superconductivity and ferromagnetism.

Findings

Magnetization of the F layer can be electrically switched at 4.2 K.

Magnetic flux states alter the Josephson critical current modulation pattern.

The device demonstrates potential for compact cryogenic memory compatible with SFQ electronics.

Abstract

We report the fabrication and testing, at 4.2 K, of an SISFS device, where S, F, and I denote a superconductor (Nb), a ferromagnetic material (permalloy), and an insulator (AlOx), respectively. The F layer covers about one half of the top electrode of the SIS Josephson junction and is positioned off-center. Electric current, I _tr, along the S electrode can change the magnetization of the F layer in such a way that, for one direction of I_tr, a magnetic flux penetrates the junction perpendicular to the layers, whereas for the opposite direction, the perpendicular magnetic flux can be removed. In the former state, the modulation pattern of the Josephson critical current, Ic, in the magnetic field, H, may acquire minimum near H=0, and restores its usual shape with maximum in the second state. These states can be used for building a compact cryogenic memory compatible with single flux quantum electronics.