Quantitative stray field imaging of a magnetic vortex core

Abstract

Thin-film ferromagnetic disks present a vortex spin structure whose dynamics, added to the small size (≈10 nm) of their core, has earned them intensive study. Here we use a scanning nitrogen-vacancy (NV) center microscope to quantitatively map the stray magnetic field above a 1-μm-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 imper..