Fermi level dependence of magnetism and magnetotransport in the magnetic topological insulators Bi$_{2}$Te$_{3}$ and BiSbTe$_{3}$ containing self-organized MnBi$_{2}$Te$_{4}$ septuple layers

TL;DR

This study investigates how the Fermi level influences magnetism and magnetotransport in magnetic topological insulators with MnBi2Te4 layers, revealing that the anomalous Hall effect is governed by Berry curvature and can be controlled via Fermi level tuning.

Contribution

It demonstrates that the magnetic properties are unaffected by Fermi level shifts, and the anomalous Hall effect is primarily intrinsic and Berry-phase driven, enabling Fermi level control of Hall responses.

Findings

Fermi level position does not affect magnetic anisotropy or Curie temperature.

The anomalous Hall effect is dominated by intrinsic Berry curvature mechanisms.

Hall resistivity is maximized near band edges due to Berry curvature concentration.

Abstract

The magnetic coupling mechanisms underlying ferromagnetism and magnetotransport phenomena in magnetically doped topological insulators have been a central issue to gain controlled access to the magneto-topological phenomena such as quantum anomalous Hall effect and topological axion insulating state. Here, we focus on the role of bulk carriers in magnetism of the family of magnetic topological insulators, in which the host material is either Bi$_{2}$Te$_{3}$ or BiSbTe$_{3}$, containing Mn self-organized in MnBi$_{2}$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 anomalous Hall effect 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 anomalous Hall effect can be effectively managed, maximized, or turned off, by adjusting the Fermi level.