Spin-transfer torque switching in nanopillar superconducting-magnetic hybrid Josephson junctions

TL;DR

This paper reports the development of nanopillar superconducting-magnetic hybrid Josephson junctions that exhibit spin-transfer torque-induced magnetization switching, enabling significant changes in critical current and promising applications in cryogenic nonvolatile memory.

Contribution

The study introduces nanoscale hybrid Josephson junctions with magnetic barriers that demonstrate spin-transfer torque effects, a novel integration of superconductivity and spintronics.

Findings

Magnetic barriers show pseudo-spin-valve behavior at 4 K.

Current-induced magnetization switching causes 20-fold changes in critical current.

Devices demonstrate compatibility with spin-transfer torque models.

Abstract

The combination of superconducting and magnetic materials to create novel superconducting devices has been motivated by the discovery of Josephson critical current (Ics) oscillations as a function of magnetic layer thickness and the demonstration of devices with switchable critical currents. However, none of the hybrid devices have shown any spintronic effects, such as spin-transfer torque, which are currently used in room-temperature magnetic devices, including spin-transfer torque random-access memory and spin-torque nano-oscillators. We have developed nanopillar Josephson junctions with a minimum feature size of 50 nm and magnetic barriers exhibiting magnetic pseudo-spin-valve behavior at 4 K. These devices allow current-induced magnetization switching that results in 20-fold changes in Ics. The current-induced magnetic switching is consistent with spin-transfer torque models for room-temperature magnetic devices. Our work demonstrates that devices that combine superconducting and spintronic functions show promise for the development of a nanoscale, nonvolatile, cryogenic memory technology.