ESTIMA was devoted to the detailed investigation of magnetic proximity effects (MPE) in heterostructures incorporating topological insulators (TI) and magnetic insulators (MI). During these two years, the experienced researcher has worked on the growth and characterization of these TI/MI heterostructures. The TI films were the (Bi,Sb)2(Se,Te)3 family of compounds, whereas the selected magnetic materials for the project were the insulators EuS, YIG or Tm3Fe5O12 (TIG), which were chosen based on published results. Such previous reports showed significant evidence of MPE in the TI, albeit with indirect techniques, such as charge transport and spin-polarized neutron scattering. During the implementation of ESTIMA, we focused in the use of x-ray absorption spectroscopy techniques including x-ray magnetic circular dichroism (XMCD) to understand the origin of MPE in TI/MI heterostructures. Because of its element-sensitive nature, the XMCD results are free of ambiguities of magnetism induced by material interface diffusion, providing a definite answer on the origin of magnetism. These investigations revealed that there is actually no induced magnetic moment originating at the surface of the (Bi,Sb)2(Se,Te)3 topological insulator material in contact to any of the selected MIs, contrary to previous reports on such structures.
Results of ESTIMA were presented by the experienced researcher in 5 contributed talks in national and international conferences. They also yielded 4 scientific peer-review publications in high impact journals, and a couple more are in preparation. Press releases related to these results were publicized in the ESTIMA twitter account and ICN2 webpage.