Effects of Substrates on the Self-Assembling of FePt Nanocrystals
ALABAMA UNIV TUSCALOOSA CENTER FOR MATERIALS FOR INFORMATION AND TECHNOLOGY
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Fe48Pt52 nanoparticles were synthesized by the simultaneous chemical reduction of platinum acetylacetonate and thermal decomposition of iron pentacarbonyl. As-prepared the particles were spherical with an average diameter of 3 nm and a polydispersity of less than 5. The particles were superparamagnetic and had a fcc structure. Highly ordered self-assembled supererystals of particles were formed in TEM grids by deposition from dispersions in hydrocarbon solvents. Nanoparticles deposited on amorphous carbon-coated and SiO2-coated Cu grids tend to assemble into small domains of hexagonal arrays. Larger domains of hexagonal arrays formed on Si3N4 membrane TEM grids. For thin multi layers, the FePt nanoparticles tends to assemble into hexagonal close-packed lattices ABABAB stacking. For the thicker multilayers, ABCABC stacking was observed. Small angle X-ray reflectivity of the particles on a Si 100 substrate show highly ordered multiplanar structure with d-spacing of 6.2 nm. The coercivity of self-assembled FePt films strongly depended on the annealing temperature. After annealing at 700 deg C for 30 minutes, the particles transformed from FCC to FCT phase and the coercivity of film increased up to 11570 Oe. However, the particle size increased to 16 nm due to sintering.
- Properties of Metals and Alloys
- Electricity and Magnetism
- Solid State Physics