In zero magnetic field the electrical resistivity, ρ(0, T), of highly-oriented-pyrolytic (polycrystalline) graphite decreases monotonically with decreasing temperature, becoming nearly constant below about 4 Kelvin. However, in an applied field, Bz, the transverse resistivity component, ρxx(Bz, T), goes through a maximum as a function of temperature at about 25°K. The size of the maximum increases as the field increases. A natural single crystal of graphite also exibits a maximum, but it is modified by Shubnikov-de Haas oscillations of ρxx. We show that the maximum of ρxx at fixed field is directly related to the unexpected field dependence of ρxx at low temperatures reported in earlier work, where it was observed that the transverse conductivity component, σxx(∼- 1/ρxx), decreases more slowly with field than expected on the basis of a simple two-band model. Calculations of the field and temperature dependence of σxx in graphite are needed, for fields just below and in the quantum limit.
ASJC Scopus subject areas
- Materials Science(all)