Low Temperature Anomalies in the Thermoelectric Power of Highly Oriented Graphite

Abstract

The magnetic field dependence of the thermomagnetic tensor components β_xx and β_yx for a high quality kish graphite specimen is studied in the temperature range 1.5–15 K with application of the field up to 0.1 T. β is a more fundamental quantity than thermoelectric power. β_xx shows a negative dip at 3.8 K and a sharp peak at 11 K in zero magnetic field. With application of magnetic field the temperatures for the dip and peak change in complicated ways. The peak disappears when a filed of 0.1 T is applied. β_yx is negative and decreases with increasing temperature. At temperatures below 4 K β_xx shows a positive peak at a field around 0.01 T in the field dependence. The previous theory for the anomaly of β_xx around 4 K is extended to the case with magnetic field. The observed behavior for β_xx in weak field region is ascribed to the trigonal band warping effect.