Ferromagnetic resonance assisted optomechanical magnetometer

TL;DR

This paper presents a hybrid optomechanical magnetometer leveraging ferromagnetic resonance and mechanical modes in a microsphere, achieving high sensitivity for detecting oscillating magnetic fields at GHz frequencies.

Contribution

It introduces a novel hybrid system combining ferromagnetic resonance with optomechanical sensing, enabling high-speed magnetic field detection with tunable sensitivity.

Findings

Peak sensitivity better than 900 pT/Hz^{1/2} at 206 MHz

Sensitivity around a few nT/Hz^{1/2} up to GHz frequencies

Demonstrates tunability of resonance frequency via static magnetic field

Abstract

The resonant enhancement of mechanical and optical interaction in optomechanical cavities enables their use as extremely sensitive displacement and force detectors. In this work we demonstrate a hybrid magnetometer that exploits the coupling between the resonant excitation of spin waves in a ferromagnetic insulator and the resonant excitation of the breathing mechanical modes of a glass microsphere deposited on top. The interaction is mediated by magnetostriction in the ferromagnetic material and the consequent mechanical driving of the microsphere. The magnetometer response thus relies on the spectral overlap between the ferromagnetic resonance and the mechanical modes of the sphere, leading to a peak sensitivity better than 900 pT Hz$^{-1/2}$ at 206 MHz when the overlap is maximized. By externally tuning the ferromagnetic resonance frequency with a static magnetic field we demonstrate sensitivity values at resonance around a few nT Hz$^{-1/2}$ up to the GHz range. Our results show that our hybrid system can be used to build high-speed sensor of oscillating magnetic fields.