Quantifying the magnetic anisotropy of individual nanomagnets embedded in biological entities

Nanomagnets can nowadays be found in a myriad of applications as diverse as data storage, tissue engineering or cancer theragnostic. All these applications rely on the magnetic properties of the nanomagnets which are mostly determined by their magnetic anisotropy. Despite its importance, the magnetic anisotropy of the individual magnetic nanostructures is unknown. Indeed, the implementation of magnetic nanoparticles relies on average values obtained by measuring a plethora of dissimilar entities. Here we present a method capable of working out the magnetic anisotropy constant and the magnetic easy axis of individual magnetic nanostructures embedded in biological entities by combining scanning transmission X-ray microscopy using an axi-asymmetric magnetic field with theoretical simulations based on the Stoner−Wohlfarth model. This method may be considered general and be applied to any nanomagnetic system.