  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 (DFT) 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 in weak and
ferromagnetic so that magnetic order of the monolayers is preserved in the
heterobilayers providing thereby a van der Waals heterostructure that combines
two monolayers with different magnetic order. Interlayer exchange should lead
both to exchange bias and to the emergence of hybrid collective modes that 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.
