Magnetoresistance of composites based on graphitic disks and cones

We have studied the magnetotransport of conical and disk-shaped nanocarbon particles in magnetic fields $\mid B\mid \le 9\mathrm{T}$ at temperatures $2\le T\le 300\mathrm{K}$ to characterize electron scattering in a three dimensional disordered material of multilayered quasi 2D and 3D carbon nanoparticles. The microstructure of the particles was modified by graphitization at temperatures ${1600}^{\circ }\mathrm{C}$ and ${2700}^{\circ }\mathrm{C}$. We find clear correlations between the microstructure as seen in transmission electron microscopy and the magnetotransport properties of the particles. The magnetoresistance measurements showed a metallic nature of samples and positive magnetoconductance which is a signature of weak localization in disordered systems. We find that the magnetoconductance at low temperatures resembles quantum transport in single-layer graphene despite the fact that the samples are macroscopic and three dimensional, consisting of stacked and layered particles, which are randomly oriented in the bulk sample. This graphene-like behaviour is attributed to the very weak interlayer coupling between the graphene layers.