Measuring the magnetic moment density in patterned ultrathin ferromagnets with submicron resolution
Abstract
We present a new approach to infer the surface density of magnetic moments Is 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 Is 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 Is 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.