Atomic and Electronic Structures of the Interfaces between Perovskite La_0.75Sr_0.25MnO₃ and Brownmillerite SrCoO_2.5

Abstract

Epitaxial thin films composed of perovskite and brownmillerite oxides have received increasing attention because of the novel phenomena found in these systems. Herein, the atomic and electronic structures of the La0.75Sr0.25MnO3/SrCoO2.5 interface have been studied using first‐principles calculations. From the perspective of polarity compensation, three types of possible interface models are constructed, which have different interface terminations or orientation relationship. In the model where the [100] direction of SrCoO2.5 is parallel to the interface, the interface is polar. The way to compensate polarity is atomic reconstruction. For the model with the [100] direction of SrCoO2.5 perpendicular to the interface, there are two possible interface terminations. One is nonpolar. The other is polar, but its polarity can be compensated by electronic redistribution, i.e., the valence change of Mn from +3 to +4 at the interface, as consistently revealed by the change of the bond valence sums and magnetic moments of Mn ions. For this model with electronic redistribution, accompanied by the valence change, the MnO6 octahedra near the interface have the largest distortion compared with the other two models. The density of states around Fermi level and the magnetic coupling across the interface are also discussed.

Metallic Interface between Two Insulating Phases of La1–xSrxCoO3−δ

“…The BM and P phases of LSCO have different band gaps, and charge transfer might occur at the interface; in addition, P is a nonpolar solid while BM can be switched from a nonpolar to a polar solid by rotation of the tetrahedral chains , and thus a polar discontinuity could occur as well; finally, P and BM crystals have a significant lattice ,, and symmetry mismatch, , which could allow for spin and orbital reconstructions at the interface. Although several studies have identified structural distortions and anisotropic magnetic properties at the BM/P interfaces formed between different TMOs, ,− the occurrence of an MIT at the interface has not yet been investigated, and in general BM/P interfaces formed within the same TMO solid (e.g., La–Sr–Co–O system) are poorly studied.…”