ANOMALOUS GALVANOMAGNETIC PROPERTIES OF GRAPHITE IN THE QUANTUM LIMIT

Recent experiments on the galvanomagnetic effects of graphite in the quantum limit revealed that (1), σxyH is not a constant but depends on the field strength; (2), the resistivity ρ{variant} {equal to or succeeds} σxx-1 at low temperatures has a field dependence of ρ{variant} = H|(A + BHn), n {equal to or succeeds} 1; and (3), the ρ{variant} vs T curve has a maximum at about T = 25 K. These results cannot be explained by a simple theory. However, in consideration of the appearance of the bound states D0 and A0 in the quantum limit we can provide a qualitative explanation of the above observed results, where D correspond to donor and A represents acceptor. In the quantum limit the possibility of the transitions D+ + (-e) → D0 and A- + (+e) → A0 is pointed out. Co-existence of the ionized impurity scattering and the neutral impurity scattering explains the qualitative features of the (H,T)-dependence of the resistivity at low temperatures. At high temperatures it is necessary to consider the phonon scattering and the carrier-carrier scattering. Without the carrier-carrier scattering the (H,T)-dependence of ρ{variant} at T > 25 K cannot be explained. © 1979.