On the ferromagnetic character of (LaVO${}_3$)${}_m$/SrVO${}_3$ superlattices

The experimental observation that vanadate superlattices (LaVO${}_3$)${}_m$/SrVO${}_3$ show ferromagnetism up to room temperature [U.
L"uders {\it et al.}, Phys.\ Rev.\ B {\bf 80}, 241102R (2009)] is investigated by means of density functional theory. First, the influence of the density functional on the electronic and magnetic structure of bulk $\mathrm{L}\mathrm{a}\mathrm{V}{\mathrm{O}}_3$ is discussed. Second, the band structure of a (LaVO${}_3$)${}_m$/SrVO${}_3$ slab for $m=5$ and 6 is calculated. Very different behaviors for odd and even values of $m$ are found: In the odd case lattice relaxation results into a buckling of the interface VO${}_2$ layers that leads to spin-polarized interfaces. In the even case a decoupling of the interface VO${}_2$ layers from the LaO layers is obtained, confining the interface electrons into a two-dimensional electron gas. The orbital reconstruction at the interface due to the lattice relaxation is discussed.