  MnBi$_2$Te$_4$, a two-dimensional magnetic topological insulator with a
uniaxial antiferromagnetic structure, is an ideal platform to realize quantum
anomalous Hall effect. However, the strength of magnetic interactions is not
clear yet. We performed systematic studies on the magnetization and angle
dependent magnetotransport of MnBi$_2$Te$_4$ single crystal. The results show
that the direction of the magnetic field has significant effects on the
critical field values and magnetic structure of this compound, which leads to
different magnetotransport behaviors. The field-driven reorientation
transitions can be utilized to estimate the AFM interlayer exchange interaction
coupling and uniaxial magnetic anisotropy D. The obtained Hamiltonian can well
explain the experimental data by Monte Carlo simulations. Our comprehensive
studies on the field-driven magnetic transitions phenomenon in MnBi$_2$Te$_4$
provide a general approach for other topological systems with
antiferromagnetism.
