Theory of magnetism in the van der Waals magnet CrI3

We study the microscopical origin of anisotropic ferromagnetism in the van der Waals magnet CrI3. We conclude that the nearest-neighbor exchange is well described by the Heisenberg-Kitaev-F (HKF) model, and we also find a nonzero Dzyaloshinskii-Moriya int