Stacking-controlled magnetic anisotropy switching in bilayer Janus Mn₂Cl₃Br₃

Bilayer Janus Mn₂Cl₃Br₃ exhibits intriguing tunable magnetic anisotropy energy (MAE), governed by stacking configurations and halogen-specific orbital interactions. Using density functional theory (DFT), we find that AA stacking in Mn₂Cl₃Br₃ induces a MAE transition from in-plane to out-of-plane orientation, which is absent in bilayer Mn₂Br₃I₃ and Mn₂Cl₃I₃. This switching is driven by a compressed Mn-Br interlayer distance that amplifies the positive contribution of MAE from the p_x and p_y interaction of Br while suppressing the p_z-p_y contributions. In contrast, bilayer Janus Mn₂Br₃I₃ and Mn₂Cl₃I₃ preserve in-plane MAE due to the negative contribution of the p_z-p_y interaction of I atoms. Stacking-dependent magnetic exchange interactions further modulate the MAE in bilayer Janus Mn₂Cl₃Br₃ with AA stacking exhibiting enhanced vertical magnetic exchange anisotropy critical for MAE switching. In contrast, AB stacking preserves in-plane MAE due to suppressed magnetic interlayer coupling. The interplay of halogen orbital engineering and stacking order offers a versatile pathway to tune the magnetic anisotropy in van der Waals magnets for designing 2D spintronic materials.