Magneto-thermopower and planar Hall effect in Sb₂Te₃ epitaxial films^*

Even though the sesqui-chalcogenide Sb₂Te₃ is a well-known thermoelectric material, the effect of the magnetic field on its Seebeck coefficient remains unexplored [1]. The measurements of magneto-thermopower are particularly significant since Sb₂Te₃ has been established as a topological insulator and may exhibit exotic magneto-thermal transport. Here, we report measurements of magneto-thermopower (MTP), anisotropic magnetoresistance (AMR) and planar Hall effect (PHE) on Sb₂Te₃ thin films grown epitaxially on (0001)-face of sapphire with pulsed laser ablation technique. The film exhibits metallic behaviour with a room temperature charge carrier density and mobility of an order of magnitude ~ 10¹⁹ cm^-3 and ~ 10² cm²V^-1S^-1, respectively. The non-linear field dependence of the Hall coefficient below 30 K suggests a dominant two-carrier transport at lower temperatures. We achieve a nominal room temperature Seebeck coefficient of ~ + 51.0 μV/K, which decreases with temperature and becomes ~ - 3.4 μV/K at 10 K. The sign crossover of the Seebeck coefficient occurs around 30 K. The out-of-plane application of a moderate magnetic field (≤ 9 T) at 300 K enhances the MTP by more than 9%. We observe AMR and PHE amplitudes of an order of magnitude larger than in Bi₂Te₃ [2,3]. The study of MTP, AMR and PHE on non-magnetic Sb₂Te₃ epitaxial thin films may find applications in the field of thermoelectric generation and the development of Hall sensors.