Synthesis and phase transition of self-assembled FePd and FePdPt nanoparticles

Fe54Pd46 nanoparticles were prepared by the simultaneous chemical reduction of palladium acetylacetonate and iron chloride. The particle size can be tunable from 2 to 10 nm by controlling the amount of surfactants. Similarly, Fe50PdxPt50-x (x=8, 15, 25) nanoparticles were prepared by the simultaneous reduction of palladium acetylacetonate, platinum acetylacetonate, and iron chloride. The average diameter for the Fe50PdxPt50-x particles was always 3.5 nm and independent of the amount of surfactants. Films of the particles were cast onto silicon wafers from hydrocarbon dispersion. The coercivity of Fe54Pd46 nanoparticles increases with annealing temperature up to 550 degreesC, indicating fcc to fct phase transition. After further increasing the annealing temperature, the coercivity of the Fe54Pd46 nanoparticles decreased, suggesting the formation of a soft magnetic phase. This new phase (Fe3Pd) was confirmed from x-ray diffraction measurements. For Fe50PdxPt50-x nanoparticles, the coercivity increases to more than 10 kOe with annealing temperature up to 650 degreesC (x=8). With increasing Pd content, the coercivity of the Fe50PdxPt50-x nanoparticles decreased, as expected since the anisotropy energy of bulk FePd material is only one third of that of bulk FePt. (C) 2004 American Institute of Physics.