Symmetry and lattice mismatch induced strain accommodation near and away from correlated perovskite interfaces

Abstract

Distinct MnO6 octahedral distortions near and away from the La0.67Sr0.33MnO3/SrTiO3(001) (LSMO/STO) interface are quantified using synchrotron x-ray diffraction and dynamical x-ray diffraction simulations. Three structural regions of stress accommodation throughout the film thickness were resolved: near the LSMO/STO interface, intermediate region farther from the interface, and the main layer away from the interface. The results show that within the first two unit cells stress is accommodated by the suppression of octahedral rotations in the film, leading to the expansion of the c-axis lattice parameter. Farther from the interface film structure acquires octahedral tilts similar to thicker perovskite films under tensile stress, leading to a reduced c-axis parameter. We demonstrate that these regions are related to two different strain coupling mechanisms: symmetry mismatch at the interface and lattice mismatch in the rest of the film. The findings suggest new routes for strain engineering in correlated perovskite heterostructures.

Impact of interfacial coupling of oxygen octahedra on ferromagnetic order in La0.7Sr0.3MnO3/SrTiO3 heterostructures

“…Such an expansion of the LMSO c lattice constant is an unusual behavior, since an out-of-plane compression of LSMO is expected for the tensile strain at the STO/LSMO interface. Previous coherent Bragg rod analysis and synchrotron X-ray diffraction have also indirectly reported the occurrence of a c expansion for the first 2–3 unit cells of LSMO thin film growth on STO2143. This unexpected expansion indicates that strain is not primarily governing the LSMO structural properties at the interface, but that OOR mismatch is the significant factor.…”

“…thick film adjacent to STO19; as an alternative, the breakdown of ferromagnetism and metallic conductivity was attributed to the effect of strain and tetragonal distortions leading to spin canting and ultimately antiferromagnetic order132021; as a further alternative, phase separation into coexisting antiferromagnetic insulating and ferromagnetic metallic mesoscopic regions was proposed2223; moreover, interfacial orbital reconstruction might occur destroying the double-exchange interaction close to the interface242526; additionally, there might be interfacial charge transfer18272829. The intimate coupling between metallic conductivity and ferromagnetism that is implied by the double exchange mechanism30 could even be absent in very thin layers, since intrinsic defects such as cation disorder lead to the localization of charge carriers117.…”

“…Another important parameter for structural accommodation is the rotation of the BO 6 oxygen octahedra, which might especially occur at chemically sharp and coherent interfaces between two perovskites with differences in lattice constant and tolerance factor. Recent studies report that changes of BO 6 oxygen octahedra rotation play a decisive role in determining the magnetocrystalline anisotropy21343536.…”

Origin of the metal-insulator transition in ultrathin films ofLa2/3Sr2/3MnLiao1, Li2, Gao3 et al. 2015Phys. Rev. B894571View full textAdd to dashboardCite

“…indicates a gradual evolution of the film toward the bulk. Because of the difference in chemical composition [25] and lattice structure [26], the physical properties near surface and the interface cannot be the same as the inside of the film. This will result in a difference in overall film property from the bulk, especially when film is not thick enough.…”

Symmetry‐Driven Atomic Rearrangement at a Brownmillerite–Perovskite Interface

“…[5][6][7][8][9][10][11][12][13][14][15][16] Symmetry mismatch occurs when the interface is formed from two non-isostructural materials such as an orthorhombic film on a cubic substrate, or even materials consisting of different coordination environments.…”