Structural, magnetic, and electronic properties of high moment FeCo nanoparticles

Soft-magnetic Fe55Co45 alloy nanoparticles have been successfully synthesized by the polyol reduction process followed by annealing under argon. The diethylene glycol (DEG) was used as solvent and reducing agent simultaneously in this process. The synthesized samples of nanoparticles were annealed at 873 K for different times. The alloy formation processes, the evolution of the microstructure, the magnetic properties, and the DOS calculation have been investigated before and after samples annealing. The X-ray diffraction of the synthesized product before annealing shows that a cobalt ferrite is spinel structure of crystallite size of about 10 nm. X-ray diffraction 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 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 emu g−1with a low coercivity of 76 Oe was obtained for the Fe55Co45nanoparticles annealed during 4 h. The local random anisotropy constant KL has been extracted. This work presents also detailed information about total, and atom projected density of state functions, as well as the magnetic moment for different atoms in Fe55Co45 alloys and cobalt ferrite.