Phonon drag thermomagnetism in bismuth at low temperatures

An anomaly is noted between reported low-temperature thermomagnetic measurements on bismuth crystals and the intrinsic theory developed by Korenblit to account for phonon drag effects. It is shown that an intrinsic description of bismuth is invalid at low temperatures, even for the purest available samples. Improved agreement between theory and experiment is obtained when an appropriate modification of the theory is made. Measurements on short bismuth crystals are reported which indicate that the large phonon drag effects observed in larger samples are quenched, possibly owing to boundary scattering of phonons in the presence of impurities.