Magnetic phase transition, enhanced magnetic anisotropy, and anomalous Hall effect in bilayer FeCl2 with different stacking orders

The controllability of magnetic order and magnetic anisotropy in van der Waals magnets is crucial for 2D spintronic applications. Based on the recent experimental few-layer FeCl2 [Zhou et al., ACS Nano 18, 10912 (2024) and Jiang et al., ACS Nano 17, 1363 (2023)], in this Letter, we use first-principles to systemically explore the effects of electric field and strain on magnetic order, magnetic anisotropy, and electronic structure of bilayer FeCl2 with different stacking orders. We demonstrate that for both AA- and AB-stacked bilayer FeCl2, the perpendicular electric field induces the change in orbital overlap between nearest-neighbor interlayer Fe atoms, resulting in the interesting transition from interlayer antiferromagnetic to ferromagnetic coupling, and the critical electric field is only 0.10 V/Å for the AB-stacking order. Simultaneously, the electric field can induce the transition of magnetic easy axis from out-of-plane to in-plane to out-of-plane due to the change in Fe-3d intraorbital hybridizations. In contrast, the in-plane strain does not trigger the phase transitions of magnetic order and magnetic easy axis, but the −5% compressive strain significantly increases the out-of-plane magnetic anisotropic energy by 69% and 124% for AA- and AB-stacking orders, respectively. Additionally, the anomalous Hall effect is predicted in AB-stacked bilayer FeCl2 without and with electric field. The present work indicates the promising applications for bilayer FeCl2 in low-energy-consumption spintronic devices such as electrical control magnetic tunnel junctions and magnetic storage devices, and will stimulate broad study on electric field and strain tuned van der Waals magnets.