High Magnetic Moment of FeCo Nanoparticles Produced in Polyol Medium

High magnetization Fe₅₅Co₄₅ alloy nanoparticles have been successfully synthesized by the polyol reduction process followed by annealing under argon. The diethylene glycol was used as solvent and reducing agent simultaneously in this process. All the synthesized samples of FeCo nanoparticles were annealed at 873 K for different times. The alloy formation processes, the evolution of the microstructure, and the magnetic properties have been investigated before and after samples annealing. The X-ray diffraction (XRD) of the synthesized product before annealing shows that a cobalt ferrite is spinel structure of crystallite size of about 10 nm. XRD analysis of the samples annealed at 873 K for different times also shows that of the FeCo alloy has been obtained by reducing the cobalt ferrite. It has been confirmed that the formation of a body-centered cubic (bcc) single-phase structure where the wt% increases with annealing times leading to a pure phase after annealing during 4 h. These results are confirmed by transmission electron microscopy study. The saturation magnetization of the Fe-Co alloys increases with annealing time, indicating an increasing homogeneity in composition and the single bcc FeCo phase formation. The highest saturation magnetization of 235 Am2 · kg^-1 with a low coercivity of 7.5 mT was obtained for the Fe₅₅Co₄₅ nanoparticles annealed during 4 h. The anisotropy constant K has been extracted and we have shown that increases with the annealing time.