Crystallographic Structure and Magnetic Properties of Co Fine Particles Encaged in Carbon Nanocapsules

Abstract

Cobalt crystallites wrapped in multilayered graphitic cages (nano-capsules) were produced by an arc discharge method. Structural characterization by X-ray diffraction and transmission electron microscopy revealed that the wrapped cobalt particles were in an fcc phase, with a trace amount of hcp Co. The particles were nominally spherical in shape, and typically 10-100 nm in diameter. The core Co metal was protected against oxidation and coalescence. Temperature dependence of the saturation magnetization ( M s ) and the coercive force ( H c ) was measured between -200° C and 800° C for powder samples, which revealed that the measured M s was consistent with that for fcc Co over that temperature range. Magnetic tapes prepared from the present powder exhibited H c of 250 Oe and 30% remanent magnetization of the M s at room temperature.