Magnetotransport in mesoscopic carbon networks

The temperature and magnetic field dependencies of the resistance of regula r carbon mesoscopic networks were studied in a temperature range from 4.2 t o 300 K and in pulsed magnetic fields up to 35 T. A crossover from Mott var iable range hopping to the Coulomb-gap Efros-Shklovskii regime has been obs erved. From the magnetoresistance versus magnetic field curves three region s were defined of low, intermediate and high magnetic field. At low fields, ln(R/R-0) is proportional to B-2. In the intermediate range, the magnetore sistance is linear with B. The dependence of magnetoresistance on B in the high-field region is much weaker. At high temperatures, where the hopping d istance is low enough to be compared with the localization length, we obser ve small negative magnetoresistance in our samples. (C) 2001 Elsevier Scien ce B.V. All rights reserved.