Direct Fabrication and Magnetic Characterization of Highly Ordered L1$_{0}$ FePt Nanoparticles

Future advanced magnetic recording media require the grains to be small and uniform with sufficient anisotropy to sustain thermal fluctuation. L1$_{0}$ phase FePt nanoparticles fit these requirements but their fabrication turns out to be difficult. Conventional methods were reported to be able to make monodispersed FePt nanoparticles with disordered structure$^{1} $. The inevitable phase transformation process is believed to be kinetically limited$^{2}$ and such issues as agglomeration and twinning are to be addressed. Here we report a novel technique that can fabricate monodispersed highly ordered FePt nanoparticles with no need for phase transformation process. In this technique, particle nucleation and growth processes happened in the gas phase and they were separated in space. Modified sputtering plasma made the ordering and particle growth processes proceed simultaneously. Uniform L1$_{0}$ FePt nanoparticles with room temperature coercivity of 8.25 kOe were achieved for particle randomly assembled film. HRTEM analysis shows that these particles have perfect octahedron shape with only {\{}111{\}} surfaces exposed. Ref: 1. Sun, S, et al, Science, 287, 1989, 2000 2. Ding, Y. et al, Appl. Phys. Lett. 87, 022508, 2005