Magnon drag thermopower of the antiferromagnetic semiconductor Li doped MnTe*

In antiferromagnetic semiconductors, magnons enhance thermopower by interacting with electrons, creating an advective transport process called the magnon drag thermpower. The hydrodynamic model of magnon drag effect (1) predicts that the magnon drag thermopower is proportional to the magnon specific heat and inversely proportional to the total number of free electrons. We report here specific heat and thermopower data of Li doped MnTe. The specific heat is analyzed in terms of an electron, phonon and magnon contribution. The thermopower is analyzed in terms of a diffusion and a magnon drag contribution. Based on the results of specific heat and Hall measurements, we calculate the diffusion thermopower and magnon drag thermopower using the hydrodynamic model. The calculation agrees well with the experiment, and shows that the magnon drag contribution is one order of magnitude larger than the diffusion thermopower. Surprisingly, the magnon-drag contribution seems to extend in the paramagnetic regime above the Neel temperature of 307 K.
(1) S. J. Watzman, et al. PRB (2016).