Broadband optomechanical transduction of nanomagnetic spin modes

TL;DR

This paper demonstrates a novel method combining cavity optomechanics and torque mixing resonance spectroscopy to measure static and dynamic properties of individual magnetic vortices, revealing complex behaviors and high-frequency resonances.

Contribution

It introduces a new technique for simultaneous measurement of magnetization, susceptibility, and spin resonances in nanomagnetic vortices at low drive levels.

Findings

Measured gyrotropic resonances up to 1.1 GHz

Revealed complex vortex behavior in pinning landscapes

Demonstrated potential for microwave-to-optical conversion

Abstract

The stable vortex state that occurs in micron-scale magnetic disks is one of the most interesting and potentially useful phenomenon in nanomagnetism. A variety of tools have been applied to study the vortex state, and collective spin excitations corresponding to harmonic motion of the vortex, but to-date these tools have measured either strongly driven vortex resonances or have been unable to simultaneously measure static properties such as the magnetization. Here we show that by combining the sensitivity of cavity optomechanics with the technique of torque mixing resonance spectroscopy, we are able to measure the magnetization, in-plane susceptibility, and spin resonances of individual vortices in the low-drive limit. These measurements elucidate the complex behavior of the vortex as it moves through the pinning landscape of the disk. Furthermore, we observe gyrotropic resonances as high as 1.1 GHz, suggesting the use of engineering defects for applications such as microwave-to-optical wavelength conversion.