Galvanomagnetic properties of AsF5-intercalated graphite

Abstract

The galvanomagnetic properties of AsF5-intercalated, highly-oriented, pyrolytic graphite (HOPG) were determined for stages 1 to 4 in the temperature range from 4.2 to 300 K using contactless eddy current methods forthe measurement of electrical conductivity and magneto-resistance and a new inductive technique forthe Hall effect. From the results p-type conduction, mean carrier mobility, total carrier concentration and charge transfer are deduced. The mobility is diminished upon intercalation due to an effective mass increase when the Fermi level is shifted by charge transferfrom AsF5 to graphite layers. Charge transfer reaches a maximum of 1/3 for stage-2 compounds. The temperature dependence of galvanomagnetic effects yields carrier scattering at crystallite boundaries for low temperatures and scattering at phonons of both intercalated layers and graphite sheets for higher temperatures. Magnetoresistance of low-sage compounds exhibits anomalies at low temperatures resulting in an overestimation of mobility and saturation at magnetic Wd strengths where the low field approximation still should be vali? For magnetic fields of several kiloGGuss a reduction of the magnetoresistance was observed. It is suggested that these effects are due to trigonal warping of the graphite energy bands and to diffuse scattering at crystallite boundaries.