Magneto-optical response of chromium trihalide monolayers: chemical trends

Abstract

Chromium trihalides (CrI₃, CrBr₃ and CrCl₃) form a prominent family of isostructural insulating layered materials in which ferromagnetic order has been observed down to the monolayer. Here we provide a comprehensive computational study of magneto-optical properties that are used as probes for the monolayer ferromagnetic order: magnetic circular dichroism and the magneto-optic Kerr effect. Using a combination of density functional and Bethe-Salpeter theories, we calculate both the optical absorption and the magneto-optical Kerr angle spectra, including both excitonic effects and spinorial wave functions. We compare the magneto-optical response of the chromium trihalide series and we find that its strength is governed by the spin–orbit coupling of the ligand atoms (I, Br, and Cl).