Measuring the magnetic moment density in patterned ultrathin ferromagnets with submicron resolution

TL;DR

This paper introduces a novel nanoscale measurement technique using nitrogen-vacancy centers in diamond to map magnetic moment density in ultrathin ferromagnetic films with unprecedented spatial resolution, enabling detailed magnetic property analysis.

Contribution

The authors develop a new quantitative stray field measurement method with atomic-scale magnetometers to determine surface magnetic moment density in ultrathin ferromagnets at submicron resolution.

Findings

Achieved measurement of surface magnetic moment density with a few percent uncertainty.

Provided spatial resolution of approximately 100 nm², surpassing previous methods.

Demonstrated the method's capability by detecting magnetic modifications after ion irradiation.

Abstract

We present a new approach to infer the surface density of magnetic moments $I_s$ in ultrathin ferromagnetic films with perpendicular anisotropy. It relies on quantitative stray field measurements with an atomic-size magnetometer based on the nitrogen-vacancy center in diamond. The method is applied to microstructures patterned in a 1-nm-thick film of CoFeB. We report measurements of $I_s$ with a few percent uncertainty and a spatial resolution in the range of $(100$ nm)$^2$, an improvement by several orders of magnitude over existing methods. As an example of application, we measure the modifications of $I_s$ induced by local irradiation with He$^+$ ions in an ultrathin ferromagnetic wire. This method offers a new route to study variations of magnetic properties at the nanoscale.