Synthesis, structure, and magnetic properties of Fe-Co alloy nanocrystals

Fe/sub x/Co/sub 1-x/[C] (x=0.0, 0.2, 0.4, 0.5, 0.6, and 0.8, nominally) nanoparticles were prepared by a Kratschmer-Huffman carbon arc method. X-ray diffraction indicated a single disordered bcc FeCo phase (along with graphitic C), for all but the x=0.2 composition for which some fcc Co was observed. Particles had an average diameter of 50 nm from Scherrer analysis of the peak widths, and a broad size distribution based on TEM. Imaging energy filtered microscopy (GIF) showed Fe and Co to be uniformly distributed in the nanoparticles. SQUID magnetometry showed fine particle magnetism consistent with other observations of transition metal nanoparticles. A compositional dependence of the M (H=1 T) magnetization was similar to that observed in the bulk alloy Slater Pauling curve. Fe/sub 0.5/Co/sub 0.5/[C] exhibited the largest magnetizations heretofore observed in similarly produced nanoparticles.