Minority Carriers in Graphite

Quantum oscillations as a function of magnetic field in the Hall effect and thermoelectric power are studied in two samples of pressure-annealed pyrolytic graphite. Only the oscillations originating from minority-Fermi-surface carriers are discussed. de Haas-van Alphen-type frequencies are measured over a wide range of angles between the magnetic field and the $c$ axis of the Brillouin zone. The major conclusions are as follows: (i) There are at least two minority carriers in graphite; (ii) pyrolytic and natural single crystals have the same minority-Fermi-surface sections; (iii) both minority carriers observed by quantum effects very likely originate from the corners of the Brillouin zone near the $H$ points; and (iv) under the assumption that ${\gamma }_0=3.18\mathrm{}$ eV, we estimate that $\Delta =+0.004\mathrm{}$ eV.