Reduce The Self-assembly To The Ordering Temperature Of Fept Thin Films

7nm FePt nanoparticles with cubic shape and Fe₃₀Pt₇₀/Fe₃O₄ core/shell nanoparticles were synthesized by high temperature solution phase method. The transmission electron microscopy (TEM), X-ray diffraction system (XRD) and vibrating sample magnetometer (VSM) were used to characterize the particle size,microcrystal structure and magnetic property.The post annealing of 7nm FePt nanoparticles with cubic shape have been performed at the temperatures from 500 to 650°C for 60min. X-ray diffraction results showed that the chemical ordered (fct) FePt phase was formed in the sample annealed at 500oC for 1 hour. The ordering parameter increased with increasing annealing temperature. S of the assembly annealed at 570°C almost reaches 0.88. It is much higher than that of 3-4nm FePt nanoparticles. It can be summarized that the ordering temperature can be reduced by the synthesis of large size FePt nanoparticles.The post annealing of Fe₃₀Pt₇₀/Fe₃O₄ core/shell nanoparticles have been performed at the temperatures from 350 to 650°C for 60min.After annealing under a flow of forming gas (70%Ar2+30%H2) for 1h at 350°C, the iron oxide shell was reduce to Fe. When the annealing temperature above 400°C, the Fe atom in the shell diffuse to Pt-rich core, which leaded to the formation of L10 FePt. It is benefit for the forming of L10 phase that annealing Fe₃₀Pt₇₀/Fe₃O₄ core/shell nanoparticles under reductive atmosphere and diffusion of iron atoms in shell to Pt-rich core. The core/shell structure was suggested to be an effective way to reduce the ordering temperature obviously.