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 (CrI₂). We demonstrate a counter-intuitive fact that the ground state of the free-standing monolayer of CrI₂ is antiferromagnetic though the bulk possesses macroscopic ferromagnetic ordering. The interlayer interaction remains antiferromagnetic up to few-layer scenarios. The unique feature of CrI₂ 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. (paper)