Magnetoresistance of an entangled single-wall carbon-nanotube network

The resistivity (Formula presented) and magnetoresistance (MR) (Formula presented) of an entangled single-wall carbon-nanotube network are investigated. The temperature dependence of the resistivity shows a negative (Formula presented) from (Formula presented) with no resistivity minimum, which is fitted well to the two-dimensional variable-range-hopping (VRH) (Formula presented) formula with (Formula presented) The MR shows a negative (Formula presented) behavior at low magnetic field. At (Formula presented) and high magnetic field, the negative MR becomes positive. The positive MR tends to be saturated for (Formula presented) The negative MR with a positive upturn can be decomposed into a positive contribution from the two-dimensional spin-dependent VRH and a negative contribution from the two-dimensional weak localization, with some contribution of the Ni impurities in the sample found with the transmission electron microscope and by energy dispersive spectrometer analysis.