Heat capacity and magnetic studies of graphite intercalated with FeCl3 and NiCl+2

Abstract

Low-temperature specific heat (Cp) and magnetic susceptibility (χ) for the graphite intercalation compounds C6.2FeCl3 (stage 1) and C17FeCl3 and C11.3NiCl2.13 (stage 2) is reported and analyzed. The FeCl3 compounds show large anomalies in Cp at 4 and 1.7 K, respectively, while the NiCl2 compound shows a peak at 20 K. For the FeCl3 compounds, χ is less than 5×10−6 emu gm−1 at all temperatures, showing only very small anomalies, while the NiCl2 compound shows a very large peak in χ at 16 K. Possible magnetic models for these layered compounds are considered, including a spin-glass or spin-cluster glass state.