Morphological control of FePt nanoparticles has been systematically studied. By varying synthetic parameters including precursors, solvents, amount of surfactants, and heating rate of the solution, the particle size from 2 to 9 nm can be tuned with 1 nm accuracy. While most particles are spherical in shape, cubic particles can be obtained when particles are greater than 7 nm. Rod-shape nanoparticles have also been obtained. The as-synthesized nanoparticles are found to be superparamagnetic at room temperature and their blocking temperature is size dependent that increases with particle size. After annealing in a reducing atmosphere, the nanoparticles form hard magnetic films with ordered fct structure and high coercivity up to 2.7 T.

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Bimagnetic FePt/ Fe 3 O 4 nanoparticles with core/shell or heterodimer structure have been prepared using a sequential synthetic method. The dimension of both FePt and Fe 3 O 4 was tuned by varying the synthesis parameters. The as-synthesized bimagnetic nanoparticles were superparamagnetic at room temperature. After being annealed in a reducing atmosphere, the FePt/ Fe 3 O 4 bimagnetic nanoparticles were converted to a hard magnetic nanocomposite with enhanced energy products due to the exchange coupling between the hard and soft magnetic phases. It was found that the exchange coupling in nanocomposites made from the core/shell nanoparticles is stronger than that from the heterodimer nanoparticles. By tuning the dimensions of the FePt and Fe 3 O 4 phases, the energy product up to 17.8 MGOe was achieved in the annealed nanocomposites, which is 36% higher than the isotropic single-phase FePt counterpart.

FePt nanorods and nanowires have been synthesized by the reduction of Pt(acac)(2) and the thermal decomposition of Fe(CO)(5) in the presence of solvents/surfactants by simply controlling the sequence of addition of surfactants. The as-synthesized FePt nanorods and nanowires have a face centered cubic structure with average diameter of 3 nm. Length of nanorods and nanowires can be adjusted in the range of 15-150 nm by varying reaction parameters. Nanocrystalline L1(0) FePt phase with coercivity up to 24 kOe was obtained after heat treatments.