Tuning Elemental Distribution in FePt Nanoparticles through Ligand Ratio Variation

In this work, we investigated the influence of aliphatic ligands on the formation of iron–platinum nanoparticles as well as on the elemental distribution within the nanoparticles. For this, we used a thermal decomposition synthesis method in nonaqueous conditions using benzyl ether as a solvent and oleic acid and oleylamine as ligands. The nanoparticles were characterized in regard to their size and shape with transmission electron microscopy (TEM) and their elemental distribution using electron energy-loss spectroscopy (EELS). X-ray diffraction (XRD) analysis was used to verify the presence of the unordered fcc phase of FePt. Additionally, we characterized the magnetic properties of the nanoparticles to see if the elemental distribution has any major impact on the magnetic behavior. Due to the different decomposition temperatures of the iron-oleate and platinum-oleate complexes formed from the acetylacetonate precursors during synthesis, the elemental distribution in the nanoparticles is directly affected by the used ratio between the oleic acid and oleylamine ligands. While a core–shell-like structure was obtained when only using oleic acid, a rather homogeneous distribution of the elements was detected for higher amounts of oleylamine in the reaction mixture.