Abstract
FeCl3 intercalated graphite compounds exhibit a sharp maximum in magnetic susceptibility at 1.7K. By using Mossbauer spectroscopy as a characterisation tool, the authors show that this peak is dramatically enhanced as the number of iron vacancies in the intercalant lattice is increased. These results strongly suggest that the sharp susceptibility maximum is due to a spin glass transition where the iron vacancies inhibit long-range magnetic order, thus providing a new series of compounds to help elucidate the many unknown properties of the spin glass state.