Spin-orbit engineering in ferromagnetic van der Waals materials*

Recently, chromium iodide (CrI₃), bromide (CrBr₃), and chloride (CrCl₃) have received much attention due to exhibiting ferromagnetic ordering in 2D which is ideal for ultrathin magneto-optical devices. We will demonstrate that by alloying the halides, specifically by mixing Cl and Br, the magnetic easy axis can be tuned from in-plane to out-of-plane continuously. The alloying process can be extended to all three halides, giving rise to compositions such as CrClBrI, where the three halides are homogeneously mixed in the material. The crystals of CrClBrI are thin and exfoliate easily. We will present triangular phase diagrams of the mixed halides and demonstrate that (a) the Curie and Weiss temperatures can be tuned continuously, (b) a frustration regime exists in these materials near CrCl₃, and (c) a metamagnetic transition is observed in the bulk crystals of CrClBrI, reminiscent of a spin-flip transition in bilayers of CrI₃.