Observation of quantized Hall plateaus in a bulk antiferromagnet EuMnBi$_2$ with magnetically confined 2D Dirac fermions

Dirac fermions in solids have been of current interest for their unique transport properties under magnetic field. To further explore distinct magneto-transport properties, interplay between Dirac fermions and magnetic order is desirable as shown in magnetic topological insulators. In this study, we have focused on a layered bulk antiferromagnet EuMnBi$_2$, where the Bi square nets hosting quasi-2D Dirac fermion and the magnetic insulating layers stack alternatively, and demonstrated that the quantum transport of Dirac fermions is highly enriched by Eu antiferromagnetic(AFM) order. Below the AFM transition temperature, external magnetic field induces spin-flop transition of Eu moments, which suppresses the interlayer coupling between the conducting Bi layers and dramatically enhances interlayer resistivity $\rho_{zz}$. Furthermore, this high-$\rho_{zz}$ state is accompanied by plateau-like structures in the Hall resistivity and giant SdH oscillations, which signify the quantum Hall effect in a bulk magnet. [H. Masuda \textit{et al.}, Sci. Adv. \textbf{2}, e1501117 (2016)]