Fabrication of ferromagnetic iron carbide nanoparticles by a chemical vapor condensation process

Iron carbide Fe3C nanoparticles were fabricated by a chemical vapor condensation (CVC), and their structural and magnetic properties were investigated. It was found that the formation of iron carbide nanoparticles strongly depended on reaction temperature and pressure. The iron carbide was formed only above 650 °C at 101 kPa (760 Torr) but never formed in vacuum (1.33 Pa) regardless of reaction temperature. The fabricated iron carbide nanoparticles were spherical with Tc of about 240 °C. While the particles formed at 650 °C (∼30 nm) possessed a typical core-shell structure, those formed at 800 °C (∼50 nm) did not have such structure. The nanoparticles fabricated at 650 °C and 800 °C at 101 kPa, exhibited Ms of ∼125 A m2/kg whereas iHc of the former was slightly higher (∼63 kA/m) than that of the latter (∼40 kA/m).