Interplay between interlayer exchange and stacking in CrX₃ (X = Cl, Br, I)

The study of few-layer crystals with ferromagnetic (FM) order is a natural follow-up of the recent discovery of FM order in stand alone 2D crystals. And as a result, the study of the structural and magnetic interlayer interactions. Here we address the case of CrX3 (X =Cl,Br,I). All of them display FM order within the layers but have different interlayer interactions. The interlayer exchange in bulk CrCl₃ is antiferromagnetic (AFM), whereas for CrBr₃ and CrI₃ is FM. In contrast, few-layers CrBr₃ and CrI₃ present an AFM interlayer coupling. [1] Moreover, the bulk systems undergo a crystallographic phase transitions with temperature and there is evidence of an strong interplay between the crystallographic and magnetic degrees of freedom, both for the bulk and the few layer systems. [2] In this study, we address the interplay between stacking and interlayer exchange coupling for CrX₃ 2D crystals using first-principles calculations and an effective interlayer coupling model. Our results shed light on the magnetic behavior of the CrX₃ bulk and 2D crystals.

1 B. Huang, et al., Nature 546, 270 (2017).
2 M. A. McGuire, et al. , Chemistry of Materials 27, 612 (2015).