  Anomalous Hall effect (AHE) is an important transport signature revealing
topological properties of magnetic materials and their spin textures. Recently,
antiferromagnetic MnBi2Te4 has been demonstrated to be an intrinsic magnetic
topological insulator that exhibits quantum AHE in exfoliated nanoflakes.
However, its complicated AHE behaviors may offer an opportunity for the
unexplored correlation between magnetism and band structure. Here, we show the
Berry curvature dominated intrinsic AHE in wafer-scale MnBi2Te4 thin films. By
utilizing a high-dielectric SrTiO3 as the back-gate, we unveil an ambipolar
conduction and electron-hole carrier (n-p) transition in ~7 septuple layer
MnBi2Te4. A quadratic relation between the saturated AHE resistance and
longitudinal resistance suggests its intrinsic AHE mechanism. For ~3 septuple
layer MnBi2Te4, however, the AHE reverses its sign from pristine negative to
positive under the electric-gating. The first-principles calculations
demonstrate that such behavior is due to the competing Berry curvature between
polarized spin-minority-dominated surface states and spin-majority-dominated
inner-bands. Our results shed light on the physical mechanism of the
gate-tunable intrinsic AHE in MnBi2Te4 thin films and provide a feasible
approach to engineering its AHE.
