Magnetotransport in mesoscopic carbon networks

The temperature and magnetic field dependencies of the resistance of regular carbon mesoscopic networks were studied in a temperature range from 4.2 to 300 K and in pulsed magnetic fields up to 35 T. A crossover from Mott variable range hopping to the Coulomb-gap Efros-Shklovskii regime has been observed. From the magnetoresistance versus magnetic field curves three regions were defined of low, intermediate and high magnetic field. At low fields, ln(R/R₀) is proportional to B². In the intermediate range, the magnetoresistance is linear with B. The dependence of magnetoresistance on B in the high-field region is much weaker. At high temperatures, where the hopping distance is low enough to be compared with the localization length, we observe small negative magnetoresistance in our samples.