Novel ferromagnetic materials of SmCo5 nanoparticles in single-nanometer size: chemical syntheses and characterizations

We first succeeded in preparing ferromagnetic materials of SmCo5 nanoparticles in sizes of single nanometers by a chemical route using a polyol process. In order to produce ferromagnetic SmCo5 nanoparticles with a CaCu5-type structure, the chemical preparation was conducted under a molar ratio of 1:1.3 of Sm:Co as compositions of metallic precursors when tetraethylene glycol (TEG), and oleic acid and oleylamine were used as a reductant and protectant, respectively. However, XRD profiles of the products showed the presence of oxides and other by-products besides the CaCu5-type structured nanoparticles. The best metallic precursors and protective reagent to prevent oxidization under reaction were SmCl3 and Co(acac)(3), and 1-adamantanecarboxylic acid (ACA) and poly(N-vinyl-2-pyrrolidone) (PVP), respectively when TEG was used as the reducing reagent. We found that oxides and other by-products were not detected and pure SmCo5 nanoparticles with the CaCu5-type structure were prepared under the chemical condition. The SmCo5 nanoparticles coated by ACA and PVP were 6.2 nm in diameter and showed a coercivity of 1500 Oe at 300 K.