Structural origins of the properties of rare earth nickelate superlattices

Abstract

NiO 6 octahedral tilts in the LaNiO 3 /SrTiO 3 superlattices are quantified using position averaged convergent beam electron diffraction in scanning transmission electron microscopy. It is shown that maintaining oxygen octahedra connectivity across the interface controls the octahedral tilts in the LaNiO 3 layers, their lattice parameters and their transport properties.Unlike films and layers that are connected on one side to the substrate, subsequent LaNiO 3 layers in the superlattice exhibit a relaxation of octahedral tilts towards bulk values. This relaxation is facilitated by correlated tilts in SrTiO 3 layers and is correlated with the conductivity enhancement of the LaNiO 3 layers in the superlattices relative to individual films.

Correlating interfacial octahedral rotations with magnetism in (LaMnO3+δ)N/(SrTiO3)N superlattices

“…LaNiO 3 /3 u.c. SrTiO 3 ) N superlattice (bulk LaNiO 3 has an a-a-a-rotation), enhanced bond angle along the c axis accompanied by reductions of bond angle along in-plane axes has been observed in the interfacial LaNiO 3 layer, which was explained by a combined effect of octahedral connectivity and epitaxial strain 35 . A careful examination of our data suggests that the two cases could be similar, as evidenced by a larger pseudocubic c lattice constant in both cases, that is, c p /a p 41 (Fig.…”

“…Each point in the data corresponds to one certain half-order Bragg peak with assigned index X, whose HKL values can be found in Supplementary Table 1. Half-order peaks with their X index ranging from [0,12], [13,34] and [35,55] correspond to peaks with one of H,K,L half-integer, peaks with all three-half-integers, and peaks with two-half-integers, respectively. (f) Pseudocubic lattice constant along the c axis (c p ) as a function of superlattice periodicity N deduced from half-order Bragg peaks.…”

Symmetry Lowering in Extreme-Electron-Density Perovskite Quantum Wells

“…Figure 2(b) shows the GdTiO 3 unit cell viewed along ½110 o and ½001 o , and simulated and experimental PACBED patterns for these orientations. The sensitivity of PACBED to structural distortions has been demonstrated previously [26][27][28]. The PACBED patterns of the two orientation variants are distinct.…”

Orbital polarization in strainedLaNiO3: Structural distortions and correlation effects

“…Note, however, that tilt angles in superlattices might differ from those in films. 49 This behavior can be considered as a second-order structural isosymmetric transition that the LNO layer undergoes on crossing over from compressive to tensile strain, whereby the rotation pattern of octahedra changes from a 0 a 0 c − (in-plane rotation γ = 0, α = β 0) to…”