Synthesis, self-assembly, and magnetic properties of FexCoyPt100-x-y nanoparticles

FexCoyPt100-x-y alloy nanoparticles were prepared by the simultaneous reduction of cobalt acetylacetonate and platinum acetylacetonate and the thermal decomposition of iron pentacarbonyl. The relative amounts of iron, cobalt, and platinum in the particles depended on the amount of iron, cobalt and platinum charged to the reaction. As prepared, the particles were superparamagnetic and had a distorted fcc structure. The average particle diameter was 3.5 nm and the size distribution was very narrow. The particles could be dispersed in hydrocarbon solvents and formed films consisting of hexagonal close-packed particles on carbon-coated copper TEM grids. The films were sputter coated with amorphous carbon and then annealed at temperatures ranging from 550 to 700 degreesC to transform the particles to the tetragonal (L1(0)) phase. The coercivity of the annealed films increased with increasing annealing temperature. For films with a similar degree of transformation to the tetragonal phase, increasing the cobalt content decreased the coercivity of the films.