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

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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.