Proximity-induced magnetic order in topological insulator on ferromagnetic semiconductor

Introducing magnetic order into topological insulator (TI) to break the time-reversal symmetry can yield numerous fascinating physical phenomena, which brings new hope for the emerging spintronic technology. The proximity effect is regarded as a promising strategy that could advance the step for realistic application by choosing a suitable ferromagnetic layer with the merits of high Curie temperature and high compatibility with mainstream semiconductor technology. Here, we prepare a Bi₂Se₃ thin film on Si-compatible ferromagnetic semiconductor (FMS) of Mn_xGe_1−x by molecular beam epitaxy. After integration, the nonmagnetic Bi₂Se₃ exhibits an anomalous Hall signal and a clear weak localization cusp in magnetoresistance until 150 K, confirming that a high-temperature magnetism can be induced by the proximity effect. Detailed investigation of the magnetoconductance quantitatively indicates that the Bi₂Se₃ conductance suffers a transition from weak antilocalization to weak localization behavior after integrating with Mn_xGe_1−x, and an 80 meV bandgap is predicted to be opened in the surface states in Bi₂Se₃ layer due to the proximity-induced magnetism. Our results prove that the proximity effect could be an important method to achieve topological magnetism at high temperatures, and reveals its potential for the manipulation of the topological surface states.