CoPt nanoparticles were prepared by simultaneous thermally reducing Co(CH_(3)COO)_(2)and Pt(acac)_(2)in oleylamine with a small quantity of oleic acid.The composition of the particles was controlled by changing the amount of the reactants.Transmission electronic microscopy reveals that Co_(48)Pt_(52)particles with an average diameter of 8.4 nm are steadily dispersed in octane in the presence of oleylamine and oleic acid.Selected area electron diffraction indicates that the as-prepared particles have a face center cubic structure.Magnetic properties of these particles measured by a vibrate sample magnetometer yield a coercivity of 1.194×10^(4)A·m^(-1)and a saturation magnetization of 5.3 emu·g^(-1).After annealing at 650℃for 2 h under the flowing Ar,the coercivity increases to 9.552×10^(4)A·m^(-1)according to partly phase transformation from face center cubic structure to face center tetragonal structure for the nanoparticles.
