Electronic and magnetic properties of VOCl/FeOCl antiferromagnetic heterobilayers

Abstract

We study the electronic properties of the heterobilayer of vanadium and iron oxychlorides, VOCl and FeOCl, two layered air stable van der Waals insulating oxides with different types of antiferromagnetic order in bulk: VOCl monolayers are ferromagnetic (FM) whereas the FeOCl monolayers are antiferromagnetic (AF). We use density functional theory calculations, with Hubbard correction that is found to be needed to describe correctly the insulating nature of these compounds. We compute the magnetic anisotropy and propose a spin model Hamiltonian. Our calculations show that interlayer coupling is weak and hence the magnetic order of each monolayers is preserved in the heterobilayer. Thus, the heterobilayer combines antiferromagnetic and ferromagnetic orders. Interlayer exchange should lead both to exchange bias and to the emergence of hybrid collective modes that combine FM and AF magnons. The energy band of the heterobilayer show a type II band alignment, and feature spin-splitting of the states of the AF layer due to the breaking of the inversion symmetry.