FePt nanoparticles with uniform compositions were synthesized by a modified coreduction process of FeCl2·4H2O and Pt(acac)2 and then rapidly annealed in a vacuum under temperatures ranging from 500 to 700 °C. We found that the coercivities of the FePt nanoparticles were greatly enhanced by the rapid annealing in a vacuum. Negative peaks on dM curves for the annealed FePt nanoparticles demonstrate that the predominant interparticle interactions are dipolar-type rather than exchange coupling ones, which indicates that the rapid annealing in a vacuum can prevent the agglomeration of the nanoparticles. Through the heat treatment of annealing in a vacuum, monodispersed Fe_(46)Pt_(54) nanoparticles with a high coercivity of 9230 Oe were successfully fabricated.
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