Transport properties of copper-doped carbon aerogels

The magnetic susceptibility, conductivity, magnetoresistance (MR) and Hall effect of copper-doped carbon aerogels are measured and compared with corresponding results from the original carbon aerogels. The experimental results indicate that the temperature-dependent magnetic susceptibility of the copper-doped and of the original carbon aerogels is well fit by a Curie function at low temperatures. The copper-doped carbon aerogels show a higher susceptibility and spin concentration than the original carbon aerogel. After doping by copper, the materials exhibit a more linear current-voltage curve than the original carbon aerogel under the same measurement conditions. The electrical resistance of the copper-doped carbon aerogels is strikingly lower than that of the original carbon aerogels, and decreases with increasing copper content in the samples. The temperature-dependent resistivity p(T) of all of the copper-doped and original carbon aerogels can be fitted by an exp(T-1/2) dependence for T < 100 K. The copper-doped and pristine carbon aerogels follow a quadratic MR behavior Deltap/p = AB(2) in the magnetic field range B investigated (up to 5 T), except at very low temperatures (T < 4 K). (C) 2003 Elsevier Science B.V. All rights reserved.