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

TL;DR

This study uses density functional theory to explore the electronic and magnetic properties of LaVO3/SrVO3 superlattices, revealing how layer number parity influences ferromagnetism and electronic confinement at interfaces.

Contribution

It provides a detailed theoretical analysis of how odd and even layer superlattices exhibit different magnetic and electronic behaviors due to lattice relaxation effects.

Findings

Odd-layer superlattices show spin-polarized interfaces due to buckling.

Even-layer superlattices confine electrons in a two-dimensional gas.

Lattice relaxation causes orbital reconstruction at interfaces.

Abstract

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 ${\rm LaVO_3}$ 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.