A- and c-axis resistivity and magnetoresistance in graphite intercalation compounds

Abstract

The a-axis electrical resistivity and the transverse magnetoresistance (aT-MR ) of stage-2 to 6 graphite intercalation compounds (GICs) have been measured in the temperature (T) range between 4.2 and 300 K and magnetic field (H) range between 0 and 7 kOe. The data are analysed together with the results of c-axis resistivity and the longitudinal magnetoresistance (cL-MR ) reported in our previous work. For stage-2 to 5 GICs shows a metallic-like T dependence and exhibits no logarithmic behaviour, while shows a metallic-like behaviour for low stage (2), a logarithmic behaviour for the intermediate stages (3, 4) and a semiconductor-like behaviour for high stages (5, 6). For all stages the sign of aT-MR is positive, while the sign of cL-MR is negative for the intermediate stages (3-5) and positive for low stages in low T and weak H. The resistivity is formed of a series connection of G-I-G (G: graphite layer, I: intercalate layer) and G-G resistivity, while is formed of a parallel connection of each layer contribution. The behaviour difference between and is discussed in the light of the role of the interior G layer forming a bottleneck to the c-axis conduction. The logarithmic behaviour and negative magnetoresistance in arise from the two-dimensional weak localization occurring in these interior G layers.