炭素材料の結晶性ならびに配向関数と磁気抵抗との関係

概要

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The relation of crystallinity and preferred orientation parameters to the magnetoresistance of carbon materials was examined. We derived the parameters for carbon samples having a planar orientation with the electric current flowing along the direction perpendicular to the orientation symmetry axis and for those having an axial orientation along the direction parallel to the orientation symmetry axis. On the basis of the magnetoresistance data on carbon materials, including pyrolytic carbons, carbon films, cokes, carbon fibers, etc., the formulae of orientation functions for planar and axial orientations were derived. The I3/I1 value derived from the orientation function is proposed as the parameter for preferred orientation in carbon materials, which changes in the range 0–2/3 for the planar orientation, 2/3 for random and point orientations and in the range 2/3–1 for the axial orientation. The parameter [Equation] shows a good correspondence to interlayer spacing d002 for all carbon materials used, which is useful to differentiate the crystallinity of highly graphitized materials.