Easy control of the size and composition of FePt nanoparticles with Improved synthesis

A new synthesis of FePt nanoparticles with tunable size and composition has been developed. Unlike conventional synthesis methods with which it is difficult to simultaneously control the size and chemical composition of FePt nanoparticles, the new synthesis offers a convenient way to tune FePt nanoparticles with different sizes and compositions. The synthesis involves the simultaneous decomposition of Fe(3)(CO)(12) and reduction of Pt(acac)(2) in diethylene glycol. Fe(3)(CO)(12) is a powder (nonvolatile) which is critical in governing the FePt particle size and composition. By varying the amount of surfactants and precursors ratio [Fe(3)(CO)(12)/Pt(acac)(2)], FePt particles with tunable composition and particle size (2-8 nm) can be obtained. After high temperature annealing (similar to 600 degrees C), Fe(50)Pt(50) nanoparticles are partially transformed to the L1(0) phase as indicated by the soft and hard components in the hysteresis loops. The coercivity ranges from a few kilo-Oersted to more than 15 kOe, depending on the particle size. Dynamic coercivity measurements reveal that the large FePt particles are easier to chemically order than the small FePt particles under the same annealing condition.