Magnetothermal Oscillations and Spin Splitting in Bismuth and Antimony

A field-modulation technique for observing magnetothermal oscillations has been used to study the Fermi surfaces and spin splitting of the Landau levels in bismuth and antimony. Magnetothermal oscillations are shown to be particularly suited for such a study because of the increased relative harmonic content at low temperatures as compared to the measurement of the de Haas-van Alphen magnetization. Also, under the conditions of appreciable harmonic content it is possible to determine whether the oscillations arise from a maximum or minimum extremal area on the Fermi surface. The effective $g$ values of the carriers appear to be in reasonable agreement with other measurements where comparison is possible, and with theory.