Thin films of FePt nanoparticles were prepared by co-deposition of Fe and Pt onto amorphous C films at 350C. The as-prepared films were composed of disordered nanoparticles with a face-centered cubic structure, in which twinned and multiply-twinned nanoparticles could be identified via transmission electron microscopy and electron diffraction. Atomic ordering, from a face-centered cubic to an L10 structure, was monitored by in situ transmission electron microscopic observations during heating up to 750C. Multiply-twinned (fivefold) nanoparticles of the L10 FePt phase were observed for the first time by high-resolution transmission electron microscopy. In these nanoparticles, the crystallographic c-axes of the L10 structure were oriented parallel to the film plane in each segment.

The Investigation of Multiply Twinned L10-Type FePt Nanoparticles by Transmission Electron Microscopy. A.Kovács, K.Sato, G.Sáfrán, P.B.Barna, Y.Hirotsu: Philosophical Magazine, 2004, 84[20], 2075-81