Carbon-coated Fe-Co(C) nanocapsules prepared by arc discharge in methane

Characterization and magnetic properties of Fe-Co(C) nanocapsules were investigated systematically by means of x-ray diffraction, Mossbauer spectroscopy, x-ray photoelectron spectroscopy, transmission electron microscopy, energy dispersive spectroscopy analysis, chemical analysis, oxygen determination, and magnetization measurement. The effects of elemental carbon, decomposed from a methane atmosphere in carbon arc process, on the phase structures, magnetic states and surface characterization were studied. Carbon atoms favor forming a new core/shell type structure, consisting of a carbon coating and a core containing a carbon solution. The mechanism of formation of the nanocapsules as well as origin of ferromagnetism and paramagnetism are discussed. (C) 1999 American Institute of Physics. [S0021-8979(99)09523-7].