Functionalization of FeCo alloy nanoparticles with highly dielectric amorphous oxide coatings

FeCo alloy nanoparticles have been prepared by using a two step modified polyol process using Fe(II) chloride and Co acetate tetrahydrate as Fe and Co metal precursors. Tetraethyl silicate, aluminum isopropoxide, and zirconium(IV) acetyl acetonate were used to make amorphous SiO2, Al2O3, and ZrO2 coatings, respectively. X-ray diffraction studies showed that there are no crystalline peaks corresponding to SiO2, Al2O3, and ZrO2 because the oxide coatings of the FeCo core are amorphous in nature. The scanning electron micrograph analysis depicted the cubic nature of the particles with mean particle size of about 45 nm. The maximum saturation magnetization of 205 emu/g was achieved at 300 and 4 K. FeCo nanocomposites were screen printed as films and aligned by using an external magnetic field of 10 kOe. The microwave properties measured by in-plane ferromagnetic resonance at various frequencies indicate a minimum linewidth of approximate to 3700 Oe. (C) 2008 American Institute of Physics.