Monodisperse FePt Nanoparticles and Ferromagnetic FePt Nanocrystal Superlattices

TLDR

The authors synthesize monodisperse FePt nanoparticles by reducing platinum acetylacetonate and decomposing iron pentacarbonyl in the presence of oleic acid and oleyl amine stabilizers. The nanoparticles self‑assemble into three‑dimensional superlattices, and thermal annealing converts their disordered face‑centered cubic cores into ordered face‑centered tetragonal structures, transforming the superlattices into ferromagnetic nanocrystal assemblies. The FePt particles have controllable composition and tunable diameters from 3 to 10 nm with <5 % size variation, and the resulting ferromagnetic assemblies are chemically and mechanically robust, supporting high‑density magnetization reversal transitions.

Abstract

Synthesis of monodisperse iron-platinum (FePt) nanoparticles by reduction of platinum acetylacetonate and decomposition of iron pentacarbonyl in the presence of oleic acid and oleyl amine stabilizers is reported. The FePt particle composition is readily controlled, and the size is tunable from 3- to 10-nanometer diameter with a standard deviation of less than 5%. These nanoparticles self-assemble into three-dimensional superlattices. Thermal annealing converts the internal particle structure from a chemically disordered face-centered cubic phase to the chemically ordered face-centered tetragonal phase and transforms the nanoparticle superlattices into ferromagnetic nanocrystal assemblies. These assemblies are chemically and mechanically robust and can support high-density magnetization reversal transitions.