CRYSTALLOGRAPHIC STRUCTURE AND MAGNETIC-PROPERTIES OF CO FINE PARTICLES ENCAGED IN CARBON NANOCAPSULES

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 degrees C and 800 degrees 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 260 Oe and 30% remanent magnetization of the M(s) at room temperature.