Shubnikov–de Hass oscillations are directly observed in undoped antiferromagnetic topological insulator $\mathrm{Mn}{\mathrm{Bi}}_2{\mathrm{Te}}_4$. With increasing magnetic fields, the oscillation period decreases gradually in the magnetic transition from canted antiferromagnetism to ferromagnetism and then saturates in high magnetic fields, indicating the field-induced evolution of the band structure. From the analysis of the high-field oscillations, a nontrivial Berry phase and a small effective mass are extracted. Furthermore, rotating the magnetization of $\mathrm{Mn}{\mathrm{Bi}}_2{\mathrm{Te}}_4$ can lead to a splitting of the high-field oscillations, which suggests the enhanced asymmetry of the Weyl cones in tilted fields. Therefore, the observation of these magnetically tunable quantum oscillations clearly demonstrates the indispensable role of field in tuning the band structure or physical properties of $\mathrm{Mn}{\mathrm{Bi}}_2{\mathrm{Te}}_4$.

• Received 21 December 2021
• Revised 1 March 2022
• Accepted 22 March 2022

DOI:https://doi.org/10.1103/PhysRevB.105.155402