Microscopic route to magnetic anisotropy in higher-spin honeycomb lattice: application to CrI₃

In the past decade transition metal (TM) compounds have generated a wealth of theoretical and experimental research on frustrated magnetism, especially TM compounds that host local 1/2 moments. Spin-orbit coupling (SOC) of the TM cation sites plays a key role for the appearance and dominance of frustrated terms such as the Kitaev spin-1/2 term. Very recently it has been recognized that SOC of the anion sites is a viable route to realizing frustrated higher spin model terms from super-exchange paths [1]. We present the microscopic origin of frustrated S=3/2 model terms in d³ systems. The appearance and competition of the Kitaev term with conventional spin model terms are presented. Applications of the theory to CrI₃ and related materials are also discussed.

[1] P. P. Stavropoulos, D. Pereira, and H.-Y. Kee, Phys. Rev. Lett. 123, 037203 (2019)