An antiferromagnetic two-dimensional material: Chromium diiodides monolayer

The two-dimensional（2D） ferromagnetic materials and the related van der Waals homostructures have attracted considerable interest, while the 2D antiferromagnetic material has not yet been reported. Based on first-principles calculations, we investigate both electronic structures and magnetic orderings of bulk and monolayer of chromium diiodides（CrI;）. We demonstrate a counter-intuitive fact that the ground state of the free-standing monolayer of CrI;is antiferromagnetic though the bulk possesses macroscopic ferromagnetic ordering. The interlayer interaction remains antiferromagnetic up to few-layer scenarios.The unique feature of CrI;makes it an ideal workbench to investigate the relation between magnetic couplings and interlayer van der Waals interactions, and may offer an opportunity to 2D antiferromagnetic spintronic devices.