Giant magnetoresistance amplifier for spin-orbit torque nano-oscillators

TL;DR

This paper demonstrates a significant enhancement in the microwave output power of spin-orbit torque nano-oscillators by integrating a ferromagnetic reference layer to utilize giant magnetoresistance, improving their practicality for applications.

Contribution

The authors introduce a method to boost nano-oscillator power by adding a ferromagnetic layer to leverage giant magnetoresistance, a novel approach for these devices.

Findings

Output power increased by nearly three orders of magnitude.

GMR provides larger magnitude than AMR for power enhancement.

Different angular dependences of GMR and AMR enable the power boost.

Abstract

Spin-orbit torque nano-oscillators based on bilayers of ferromagnetic (FM) and nonmagnetic (NM) metals are ultra-compact current-controlled microwave signal sources. They serve as a convenient testbed for studies of spin-orbit torque physics and are attractive for practical applications such as microwave assisted magnetic recording, neuromorphic computing, and chip-to-chip wireless communications. However, a major drawback of these devices is low output microwave power arising from the relatively small anisotropic magnetoresistance (AMR) of the FM layer. Here we experimentally show that the output power of a spin-orbit torque nano-oscillator can be enhanced by nearly three orders of magnitude without compromising its structural simplicity. Addition of a FM reference layer to the oscillator allows us to employ current-in-plane giant magnetoresistance (CIP GMR) to boost the output power of the device. This enhancement of the output power is a result of both large magnitude of GMR compared to that of AMR and different angular dependences of GMR and AMR. Our results pave the way for practical applications of spin-orbit torque nano-oscillators.