Adjustable spin torque in magnetic tunnel junctions with two fixed layers

TL;DR

This paper introduces a novel magnetic tunnel junction design with two fixed layers, enabling adjustable spin torque for improved control in spintronic devices like MRAM and magnetic sensors.

Contribution

The study presents a new MTJ structure with dual fixed layers, allowing tunable spin torque and enabling direct comparison of spin-torque sources and thermal effects.

Findings

Demonstrated adjustable spin torque via dual fixed layers

Quantified contributions of tunneling and metallic electrons to spin torque

Analyzed Joule heating effects in the new MTJ design

Abstract

We have fabricated nanoscale magnetic tunnel junctions (MTJs) with an additional fixed magnetic layer added above the magnetic free layer of a standard MTJ structure. This acts as a second source of spin-polarized electrons that, depending on the relative alignment of the two fixed layers, either augments or diminishes the net spin-torque exerted on the free layer. The compound structure allows a quantitative comparison of spin-torque from tunneling electrons and from electrons passing through metallic spacer layers, as well as analysis of Joule selfheating effects. This has significance for current-switched magnetic random access memory (MRAM), where spin torque is exploited, and for magnetic sensing, where spin torque is detrimental.