High-resolution imaging of 3D stray-field components with a Fe ₃ O ₄ nanoparticle sensor

-nanoparticle sensor to detect nanoscale magnetic domains, domain walls, and magnetic vortices (resolution ∼5 nm), and our findings demonstrate its potential in imaging both out-of-plane and in-plane magnetic-field components. Our technique overcomes the limitations of 3D stray-field detection and high-resolution imaging and provides the possibility of observing both out-of-plane and in-plane magnetic field components with a 5 nm resolution, thereby paving the way for the development of future spin-based devices.