2-D localization in single wall carbon nanotube network synthesized by arc-plasma method

Resistivity rho(T) and magnetoresistance (MR), ((rho(H)-rho(H=0))/rho(H=0), of the entangled single wall carbon nanotube (SWCN) network are studied. T he temperature dependence of the resistivity shows the negative d rho/dF fr om T=4.2K to 300K, which fits well to the 2-dimensional variable range hopp ing (VRH) (rho(T)=rho(0)exp(T-0/T)(1/3))) formula with T-0=259.2 K. The ove rall MR shows a negative HL behavior at low magnetic field. At T less than or equal to 3.8K and high magnetic field, the negative MR turns to be posit ive. The positive MR becomes saturating for H>10 Tesla. The negative MR wit h a positive upturn can be decomposed into a positive contribution from the 2-dimensional spin-dependent VRH and a negative contribution from the 2-di mensional weak localization (WL). Moreover we report the interesting chain- like ring structures found from the by-products of SWCNs synthesized by the are-plasma method.