Iron–platinum nanoparticle
Iron–platinum nanoparticles (FePt NPs) are 3D superlattices composed of an approximately equal atomic ratio of Fe and Pt. Under standard conditions, FePt NPs exist in the face-centered cubic phase but can change to a chemically ordered face-centered tetragonal phase as a result of thermal annealing.
Source: Wikipedia — Iron–platinum nanoparticle (CC BY-SA 4.0)