Network analyzer measurements of spin transfer torques in magnetic tunnel junctions

TL;DR

This paper introduces a straightforward network-analyzer method to quantitatively measure the bias dependence of spin transfer torque in magnetic tunnel junctions, providing a new tool for spintronics research.

Contribution

The paper presents a novel network-analyzer technique for measuring spin transfer torque bias dependence in magnetic tunnel junctions, offering a simpler alternative to existing methods.

Findings

Quantitative measurement of spin torque bias dependence.

Comparison with time-domain spin-torque ferromagnetic resonance.

Demonstration of the technique's effectiveness in magnetic tunnel junctions.

Abstract

We demonstrate a simple network-analyzer technique to make quantitative measurements of the bias dependence of spin torque in a magnetic tunnel junction. We apply a microwave current to exert an oscillating spin torque near the ferromagnetic resonance frequency of the tunnel junction's free layer. This produces an oscillating resistance that, together with an applied direct current, generates a microwave signal that we measure with the network analyzer. An analysis of the resonant response yields the strength and direction of the spin torque at non-zero bias. We compare to measurements of the spin torque vector by time-domain spin-torque ferromagnetic resonance.