Abstract
Three-dimensional (3D) arrangements of atoms and defects strongly influence the properties and functionalities of many materials. Correlating 3D atomic structure and chemical order/disorder with material properties is essential to understand microscopic mechanisms and engineer new materials. Here, we use iron-platinum nanoparticles as a model system to reveal chemical order/disorder and magnetic properties at the single-atom level. We determined the 3D coordinates of 6,569 iron and 16,627 platinum atoms in an iron-platinum nanoparticle with 22pm precision. We identified rich structural variety and chemical order/disorder including 3D grains with different compositions, orientations, anti-phase boundaries, anti-site point defects and swap defects. We show for the first time that measured 3D atomic coordinates and chemical species with defects can be used as direct input for density functional theory calculations of material properties such as local magnetocrystalline anisotropy. Our work not only opens the door to determining the 3D chemical order/disorder of a wide range of nanostructured materials with atomic resolution, but also promises to understand structure-property relationships at the most fundamental scale.
