The investigation of multiply twinned L1₀-type FePt nanoparticles by transmission electron microscopy

Thin films of FePt nanoparticles were prepared by co-deposition of Fe and Pt on to amorphous C films kept at 350°C. As-prepared films were composed of disordered Fe–Pt nanoparticles with a fcc structure, where twinned and multiply twinned Fe–Pt nanoparticles could be identified by transmission electron microscopy (TEM) and electron diffraction. Atomic ordering from fcc to L10 structure was followed by in-situ TEM observation during heating up to 750°C. Multiply twinned (fivefold) nanoparticles of the L10 FePt were observed for the first time by high-resolution TEM observation. In these nanoparticles the crystallographic c axes of L10 structure is oriented parallel to the film plane in each segment. The stability of the fivefold FePt nanoparticles is briefly discussed.