Phase Transformation, Coalescence, and Twinning of Monodisperse FePt Nanocrystals

The phase transformation, coalescence, and twin structure of thermally annealed 6 nm FePt nanocrystals under high vacuum on an amorphous carbon surface have been investigated. A1-FePt phase to L10-FePt phase transformation occurs at 530°C. The multilayered nanocrystal assemblies coalesce to form larger grains at 600°C. These coalesced nanocrystals do not form a single grained structure; instead, twinning becomes a characteristic structure feature. The surface of the coalescent grains consists of {111} and (001) facets.