Measuring the ferromagnetic resonance cone angle via static dipolar fields using diamond spins

TL;DR

This paper demonstrates a novel method using diamond spins to quantitatively measure the ferromagnetic resonance cone angle and microwave field amplitude in a micro-scale ferrimagnetic sample, advancing magnetic dynamics characterization.

Contribution

The study introduces a spin echo-based approach with diamond spins to accurately measure FMR cone angles and microwave fields, providing a new tool for magnetic metrology.

Findings

Measured a cone angle of at least 6° at 0.53 G microwave field.

Validated measurements with micromagnetic simulations.

Showcased diamond spins as sensitive, calibration-free magnetic probes.

Abstract

We demonstrate quantitative measurement of the ferromagnetic resonance (FMR) precession cone angle of a micro-scale sample of vanadium tetracyanoethylene (V[TCNE]$_{x\sim 2}$) using diamond spins. V[TCNE]$_{x\sim 2}$ is a low-damping, low-magnetization ferrimagnet with potential for scalable spintronics applications. Our study is motivated by the persistent need for quantitative metrology to accurately characterize magnetic dynamics and relaxation. Recently, diamond spins have emerged as sensitive probes of static and dynamic magnetic signals. Unlike analog sensors that require additional calibration, diamond spins respond to magnetic fields via a frequency shift that can be compared with frequency standards. We use a spin echo-based approach to measure the precession-induced change to the static stray dipolar field of a pair of V[TCNE]$_{x\sim 2}$ discs under FMR excitation. Using these stray dipolar field measurements and micromagnetic simulations, we extract the precession cone angle. Additionally, we quantitatively measure the microwave field amplitude using the same diamond spins, thus forming a quantitative link between drive and response. We find that our V[TCNE]$_{x\sim 2}$ sample can be driven to a cone angle of at least 6$^{\circ}$ with a microwave field amplitude of only 0.53 G. This work highlights the power of diamond spins for local, quantitative magnetic characterization.