Magneto-thermopower of Cr-doped Sb₂Te₃ films

Thin films of topological insulators (TI) doped with 3d transition metals have received considerable research interests in recent years as the broken time reversal symmetry in these systems may lead to quantum anomalous Hall effect (QAHE) and magnetically ordered phases with novel spin textures. The sesqui-chalcogenide Sb₂Te₃ is a well-known topological material. Doping of Sb₂Te₃ with elements such as Cr, Mn, Fe and Co has the potential to lead to low carrier density ordered magnetic phases of significant fundamental and technological interest. We deposit multilayers of the type [(n=1-5 nm)CrTe₂/(m=5 nm)Sb₂Te₃]_p using pulsed laser ablation on c-plane sapphire. X-ray diffraction and high-resolution electron microscopy studies revealed a single-phase Cr-doped Sb₂Te₃ for n= 1-2 nm. These samples are ferromagnetic with out-of-plane magnetic anisotropy (PMA) as revealed by the measurements of anomalous Hall effect (AHE) and dc magnetization. We have also performed the measurements of thermopower and anomalous Nernst effect in these samples. The existence of PMA, AHE and Nernst effect in these Cr-doped low carrier density Sb₂Te₃ films throws some interesting questions related to the ordering of Cr moments in this TI, which will be discussed during the presentation.