Interlayer Stacking-Controlled Magnetism in Van der Waals Antiferromagnets.

Interlayer stacking in van der Waals (vdW) magnets offers a powerful route to tailor magnetic interactions and emergent functionalities. Here, we show that transitions from aperiodic AA/AB stacking to long-range periodic 6R order govern the coexistence and competition of ferromagnetic and antiferromagnetic ground states in room-temperature vdW antiferromagnets. Stacking-controlled interlayer coupling and symmetry breaking redefine the intrinsic origins of ferromagnetism. Atomically thin flakes with distinct stacking sequences exhibit unconventional magnetic behavior that is different from the established odd-even-layer effect in vdW antiferromagnets. Moreover, stacking-dependent magnetic competition reverses the sign of magnetoresistance (negative to positive). Importantly, all thin flakes maintain magnetic order above room temperature, with a TC of ∼340 K observed in the monolayer flake. These findings establish stacking sequences as a deterministic handle for engineering magnetic and transport properties, enabling the design of high-temperature stacking-programmable spintronic devices.