Preparation and properties of carbon-coated magnetic nanocrystallites

Carbon-coated gadolinium carbide nanocrystallites are generated by a process based on the Kratschmer-Huffman carbon-arc method of preparing fullerenes, and a novel magnetic-field-gradient separation technique is used to separate them. This separation of nanocrystalline byproducts of the carbon arc process is a prerequisite for many of the proposed applications of these materials. While the data presented pertain to ${\mathrm{Gd}}_2$ ${\mathrm{C}}_3$, this method is generally applicable to any paramagnetic or ferromagnetic compound. Structural characterization by x-ray and electron diffraction and high-resolution transmission electron microscopy reveal the presence of a single gadolinium-containing (${\mathrm{Gd}}_2$ ${\mathrm{C}}_3$) phase and excess carbon. The carbide phase exists as 10–50 nm spherical particles. SQUID magnetometry shows paramagnetic response attributed to ${\mathrm{Gd}}^{3+}$ ions.