Shubnikov-de Haas effect in low-stage acceptor-type graphite intercalation compounds.

Abstract

Low-stage acceptor-type graphite intercalation compounds (GIC's) have been synthesized with intercalants ${\mathrm{Br}}_{2}$, ICl, ${\mathrm{CuCl}}_{2}$, ${\mathrm{AlCl}}_{3}$, ${\mathrm{FeCl}}_{3}$, ${\mathrm{ICl}}_{3}$, ${\mathrm{AlCl}}_{3}$Br, ${\mathrm{SbCl}}_{5}$, and ${\mathrm{H}}_{2}$${\mathrm{SO}}_{4}$. For the GIC that could be prepared in high-quality quasi-single-crystalline form, the electronic parameters were investigated by means of magnetotransport and Hall-effect measurements in the temperature interval 1.4 KT4.2 K and in high magnetic fields (up to 35 T). In low magnetic fields for all first-stage compounds and most second-stage compounds a single Shubnikov--de Haas (SdH) frequency was observed. The angular dependence of the SdH frequency revealed a nearly cylindrical Fermi surface. However, for the second-stage compounds ${\mathrm{C}}_{16}$${\mathrm{ICl}}_{0.8}$ and ${\mathrm{C}}_{18.6}$${\mathrm{AlCl}}_{3.4}$ a more complicated Fermi surface was observed. In the case of ${\mathrm{C}}_{16}$${\mathrm{ICl}}_{0.8}$ the Fermi surface consists of two concentric cylinders, while for ${\mathrm{C}}_{18.6}$${\mathrm{AlCl}}_{3.4}$ frequency beats of two close frequencies were observed, yielding a Fermi surface in the shape of an undulating cylinder. The undulated Fermi surface possibly originates from the interaction between carbon atoms in neighboring graphite layers separated by the intercalant. The experimental data are compared to the band-structure model proposed by Blinowski and co-workers.