Lattice relaxation and ferromagnetic character of (LaVO₃)_m/SrVO₃superlattices

¹ Universität Augsburg, Institut für Physik - 86135 Augsburg, Germany, EU
² Laboratoire CRISMAT, UMR CNRS - ENSICAEN 6508 - 14050 Caen, France, EU
³ KAUST, PSE Division - Thuwal 23955-6900, Kingdom of Saudi Arabia

^(a) udo.schwingenschlogl@kaust.edu.sa

Received: 23 April 2013
Accepted: 29 July 2013

Abstract

The experimental observation that vanadate superlattices (LaVO₃)_m/SrVO₃ show ferromagnetism up to room temperature (Lüders U. et al., Phys. Rev. B, 80 (2009) 241102(R)) is investigated by means of density functional theory, and the band structure for m = 5 and 6 is calculated. A buckling of the interface VO₂ layers is found in both cases, but subtle differences in bond length lead to very different properties for even and odd values of m: in the even case, the two interface VO₂ layers effectively decouple from the adjacent LaO layers due to a strong bond length enhancement. This results into a local inversion of the orbital occupancy and to the confinement of the charge carriers. In the odd case, the amplitude of the bond length variation is smaller, so that the charge carriers spill into the deeper-lying VO₂ layers, and spin-polarised interfaces are obtained.