Synthesis and characterization of Fe-Pt based multishell magnetic nanoparticles

Iron/platinum based core-shell nanoparticles were obtained by the inverse micelles method in two stages. Due to its specificity, this method produces an intermediate amorphous iron oxide layer. In this way the nanoparticles architecture is Fe@Fe-oxide@Pt. By thermal treatment in inert atmosphere, the amorphous shell crystallize and an additional magnetically ordered FePt alloy shell is formed at the interface between the Fe oxide and the outer Pt shell (Fe@Fe3O4/Fe2O3@FePt@Pt). The properties of these composites nanoparticles are investigated by TEM, HRTEM, X-ray diffraction (XRD), X-ray Photoelectron spectroscopy (XPS) and superconducting quantum interference device (SQUID) magnetization measurements. The thermally treated nanoparticles show one order of magnitude higher coercivities than the initial Fe@Fe-oxide@Pt nanoparticles while preserving almost the same saturation magnetization. The complex magnetic behavior of these both multilayer coupled magnetic materials as a function of temperature and applied magnetic field is also discussed.