Direct ordering and shape effects of FePt nanoparticles produced by nanoparticle beam technology

Partial chemically ordered FePt nanoparticles were produced by annealing the nanoparticles in transit through the furnace from the source to the substrate. The equiaxed or polyhedral morpohology of FePt nanoparticles can be produced by tuning the temperature of nanoparticle-forming chamber. The equiaxed FePt particles were amorphous whereas the polyhedral particles showed good crystallinity. Both FePt particle assemblies were superparamagnetic without on-line heating of particles. With on-line annealing, the assembled films showed ferromagnetic behavior. The coercivity of the polyhedral FePt particle assembly was about 600 Oe, whereas that of equiaxed FePt particles was 450 Oe. The larger coercivity was attributed to the increased particle size. (c) 2005 American Institute of Physics.