Thermomagnetic effects in graphite

Abstract

Anomalous behaviors of the thermoelectric power with magnetic field and the Nernst-Ettingshausen effect in single crystal graphite, are explained by solving the coupled Boltzmann equation for carriers and phonons. The Fermi surface is approximated by the ellipsoid model instead of the Slonczewski-Weiss model. Anomalies of the thermopower and the Nernst-Ettingshausen coefficient are mainly attributed to the phonon drag component which is strongly enhanced in the presence of a magnetic field. The in-plane vibration plays a dominant role in the phonon drag effect, while the contribution from the out-of-plane mode is negligible because the velocity along the basal plane is very small. The thermoelectric power depends on the carrier concentration difference N e — N h , where N e and N h denote the electron and hole density, respectively. Therefore, the observed values of the thermopower vary from sample to sample.