Phase-modulated cavity magnon polaritons as a precise magnetic field probe

TL;DR

This paper introduces a novel spin-magnetometer using phase-modulated cavity magnon polaritons, achieving high sensitivity for detecting RF magnetic fields with potential for sub-femtoTesla measurements at room temperature.

Contribution

It presents a new magnetometry method based on phase modulation of cavity magnon polaritons, demonstrating high sensitivity and noise evasion, with prospects for further improvements and miniaturization.

Findings

Achieved a sensitivity of 2.0 pT/√Hz at room temperature.

Theoretical potential for 8 fT/√Hz sensitivity with optimization.

Demonstrated negligible pump noise and high-frequency readout.

Abstract

We describe and operate a novel spin-magnetometer based on the phase modulation of cavity magnon polaritons. In this scheme a rf magnetic field is detected through the sidebands it induces on a pump, and the experimental configuration allows for a negligible pump noise and a high frequency readout. The demonstrator setup, based on a copper cavity coupled to an yttrium iron garnet sphere hybrid system, reached a sensitivity of $2.0\,\mathrm{pT/\sqrt{Hz}}$, evading the pump noise and matching the theoretical previsions. An optimized setup can attain a rf magnetic field sensitivity of about $8\,\mathrm{fT/\sqrt{Hz}}$ at room temperature. An orders of magnitude improvement is expected at lower temperatures, making this instrument one of the few magnetometers accessing the sub-fT limit. Due to its natural applications, miniaturization and multiplexing are eventually discussed.