Quantitative stray field imaging of a magnetic vortex core

TL;DR

This paper demonstrates the use of scanning NV microscopy to quantitatively image and analyze the stray magnetic field of a magnetic vortex core in a ferromagnetic disk, revealing detailed magnetic structures and perturbations.

Contribution

It introduces a method for high-resolution, quantitative magnetic field mapping of vortex cores using NV centers, validated against micromagnetic simulations.

Findings

Successful imaging of vortex core stray fields

Detection of perturbations due to magnetic fields or imperfections

Validation of NV microscopy for nanoscale magnetic mapping

Abstract

Thin-film ferromagnetic disks present a vortex spin structure whose dynamics, added to the small size (~10 nm) of their core, earned them intensive study. Here we use a scanning nitrogen-vacancy (NV) center microscope to quantitatively map the stray magnetic field above a 1 micron-diameter disk of permalloy, unambiguously revealing the vortex core. Analysis of both probe-to-sample distance and tip motion effects through stroboscopic measurements, allows us to compare directly our quantitative images to micromagnetic simulations of an ideal structure. Slight perturbations with respect to the perfect vortex structure are clearly detected either due to an applied in-plane magnetic field or imperfections of the magnetic structures. This work demonstrates the potential of scanning NV microscopy to map tiny stray field variations from nanostructures, providing a nanoscale, non-perturbative detection of their magnetic texture.