Bulk ${\mathrm{MnBi}}_2{\mathrm{Te}}_4$ (MBT) is an intrinsic antiferromagnetic topological insulator. However, its low Néel temperature of $\sim 25$ K severely restricts its practical applications. Here, we propose a van der Waals heterostructure composed of monolayer MBT (ML-MBT) and monolayer ${\mathrm{MnBr}}_3$, an intrinsic Chern insulator possessing a high Curie temperature ($T_C\sim 200\mathrm{K}$). By employing density functional theory calculations and Monte Carlo simulations, we demonstrate that interfacing ML-MBT with ${\mathrm{MnBr}}_3$ significantly enhances the $T_C$ of ML-MBT by a factor of four to five. Electronic correlations characterized by the Hubbard parameter $U_2$ for Mn-$d$ orbitals in ${\mathrm{MnBr}}_3$ play a crucial role in governing magnetic coupling within the system. At a moderate correlation strength of $U_2=3.0\mathrm{eV}$, slight structural distortions in ${\mathrm{MnBr}}_3$ break intralayer symmetry, enabling robust interlayer ferromagnetic coupling and yielding a single, unified magnetic transition. Increasing $U_2$ reduces these structural distortions, weakens interlayer coupling, and induces two distinct magnetic transitions, indicating interlayer magnetic decoupling. Thus, the $\mathrm{MBT}/{\mathrm{MnBr}}_3$ heterostructure offers an interesting approach for controlling magnetic order and enhancing the performance of spintronic devices.

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• Electronic structure
• First-principles calculations
• Magnetic coupling
• Magnetism
• Spintronics
• Density functional theory