Chemically Synthesized FePt Binary Alloy Nanoparticles with Different Shapes

Chemically synthesized FePt nanoparticles are promising candidates for future high density magnetic recording media. In this work, FePt and FePt$_{3}$ binary alloy nanoparticles have been synthesized by thermal decomposition of iron pentacarbonyl (Fe(CO)$_{5})$ and reduction of platinum acetylacetonate (Pt (acac)$_{ 2})$ in the presence of oleic acid (OA) and oleyl amine (OY) surfactants at low refluxing temperatures. FePt$_{3}$ and FePt nanoparticles were obtained by varying the Fe:Pt molar ratio in the range of 1.4-1.7. With control of the heating rate to the refluxing temperature, nanoparticles with a size of $\sim $5 nm and with different shapes were obtained for both compositions. The particles showed very little agglomeration to an annealing temperature of 650$^{o}$C, as observed using X-Ray Diffraction (XRD) and Transmission Electron Microscopy (TEM). Magnetic measurements show that annealing at 700$^{o}$C partially transforms the FePt and FePt$_{3}$ nanoparticles from the disordered fcc phase to the ordered L1$_{0}$ and L1$_{2}$ phases, respectively. HRTEM and Mossbauer studies will be discussed in terms of the temperature and time dependent evolution of microstructure with annealing.