Fermi-level dependence of magnetism and magnetotransport in the magnetic topological insulators Bi2Te3 and BiSbTe3 containing self-organized MnBi2Te4 septuple layers

Abstract

The magnetic coupling mechanisms underlying ferromagnetism and magnetotransport in magnetically doped topological insulators (TIs) have been a central issue to gain controlled access to the magnetotopological phenomena such as the quantum anomalous Hall effect (AHE) and the topological axion insulating state. Here, we focus on the role of bulk carriers in magnetism of the family of magnetic TIs, in which the host material is either ${\mathrm{Bi}}_{2}{\mathrm{Te}}_{3}$ or $\mathrm{BiSb}{\mathrm{Te}}_{3}$, containing Mn self-organized in $\mathrm{Mn}{\mathrm{Bi}}_{2}{\mathrm{Te}}_{4}$ septuple layers. We tune the Fermi level using the electron irradiation technique and study how magnetic properties vary through the change in carrier density; the role of the irradiation defects is also discussed. Ferromagnetic resonance spectroscopy and magnetotransport measurements show no effect of the Fermi-level position on the magnetic anisotropy field and the Curie temperature, respectively, excluding bulk magnetism based on a carrier-mediated process. Furthermore, the magnetotransport measurements show that the AHE is dominated by the intrinsic and dissipationless Berry-phase-driven mechanism, with the Hall resistivity enhanced near the bottom/top of the conduction/valence band, due to the Berry curvature which is concentrated near the avoided band crossings. These results demonstrate that the AHE can be effectively managed, maximized, or turned off by adjusting the Fermi level.