Atomic and electronic structure of La2CoMnO6 on SrTiO3 and LaAlO3 substrates from first principles

Abstract

Adhesion energies, atomic structures, electronic states, and bonding nature of the La2CoMnO6(001)/SrTiO3(001) and La2CoMnO6(001)/LaAlO3(001) interfaces are systematically investigated from first principles by taking into account strain effect, electron correlation effect, and polarity continuity. A total of sixteen candidate geometries are considered for each interface, and the fundamental impact of strain on interfacial atomic structures is found to be minor, but its electronic impact is significant. For the La2CoMnO6/SrTiO3 interface where La2CoMnO6 suffers tensile strain, the 3d states of Co and Mn overlap Fermi level, demonstrating a metallic nature for this interface. Electrons are found to be injected into the Ti of SrTiO3 at this interface and spread layers away from interface, inducing an ordering of the in-plane dxy orbital. On the other hand, the compression strained La2CoMnO6/LaAlO3 interface takes on a half-metallic nature with a large degree of hybridization of interfacial Mn 3d with O 2p at Fermi level. We also find an ordering of the out-of-plane dz2 orbital for the interfacial and sub-interfacial Mn atoms and an ordering of the pz orbital for the O neighboring Mn. By applying several analytic methods, we have thoroughly characterized the electronic structure and have determined the interfacial bonding to be covalent for the La2CoMnO6/SrTiO3 interface, yet mixed covalent and ionic for the La2CoMnO6/LaAlO3 interface.