Magneto-oscillations in AsF 5-intercalated graphite

Abstract

We have observed quantum oscillations in low stage (1–3) samples of HOPG graphite intercalated with AsF 5. An inductive technique is described which allows simultaneous observation of both Shubnikov-de Haas (resistivity) and de Haas-van Alphen (magnetization) oscillations. The oscillations are interpreted in terms of a tight-binding model for the band structure, and good agreement with both band parameters and effective masses is found. The fractional charge transfer is found to be f = 0.37 for stage 1 and 0.41 for stage 2, in approximate agreement with previous determinations. As the stage 2 samples age under N 2 a new, low frequency oscillation appears in the magnetoresistance. C--axis X-ray reflections show that these samples are still of second stage, but an analysis of the X-ray intensities suggests that the amount of intercalant decreases with time. Neither the d.c. conductivity nor the period of the high-frequency oscillations charge significantly as the samples age. The analysis of X-ray reflection intensities provides a chemical charge transfer (fraction of AsF 5 converted to AsF 6 −) in good agreement with the electronic charge transfer measured above, while the changes with aging are associated with loss of unconverted AsF 5.