For perovskite oxides, ABO₃, slight octahedral distortions have close links to functional properties. While perovskite oxide heterostructures offer a good platform for controlling functionalities, atomistic understanding of octahedral distortion at the interface has been a challenge as it requires precise measurements of the oxygen atomic positions. Here we demonstrate an approach to clarify distortions at an atomic level using annular bright-field imaging in aberration-corrected scanning transmission electron microscopy, which provides precise mappings of cation and oxygen atomic positions from distortion-minimized images. This technique revealed significant distortions of RuO₆ and ScO₆ octahedra at the heterointerface between a SrRuO₃ film and a GdScO₃ substrate. We also found that structural mismatch was relieved within only four unit cells near the interface by shifting the oxygen atomic positions to accommodate octahedral tilt angle mismatch. The present results underscore the critical role of the oxygen atom in the octahedral connectivity at the perovskite oxide heterointerface.

A goal in the characterization of supported metal catalysts is to achieve particle-by-particle analysis of the charge state strongly correlated with the catalytic activity. Here, we demonstrate the direct identification of the charge state of individual platinum nanoparticles (NPs) supported on titanium dioxide using ultrahigh sensitivity and precision electron holography. Sophisticated phase-shift analysis for the part of the NPs protruding into the vacuum visualized slight potential changes around individual platinum NPs. The analysis revealed the number (only one to six electrons) and sense (positive or negative) of the charge per platinum NP. The underlying mechanism of platinum charging is explained by the work function differences between platinum and titanium dioxide (depending on the orientation relationship and lattice distortion) and by first-principles calculations in terms of the charge transfer processes.

The oxygen vacancy containing Li-rich cathode Li _1.2 Ni _0.13 Co _0.13 Mn _0.54 O _2−δ showed excellent energy density retention.

We report on our characterization of the structural, electrical, and magnetic properties of tetragonal SrRuO₃ (SRO) thin films stabilized under both compressive and tensile strain. These tetragonal films consisting of the deformed RuO₆ octahedra without rotations were coherently grown on (110)_ortho NdGaO₃ and (110)_ortho GdScO₃ substrates, which provide compressive (−1.7%) and tensile (+1.0%) strains, respectively. The ferromagnetic transition temperature T_C for the compressively strained film is found to be as high as 155 K, while T_C of the film under tensile strain is only 100 K. The longitudinal resistivity ρ_xx of the compressively strained films is lower than that of the films under the tensile strain. This is attributed to the enhanced mobility for the compressive-strain case. The magnetic anisotropy also exhibits strong dependence on the substrate-induced epitaxial strain. The film under the compressive strain has the uniaxial magnetic easy axis along the out-of-plane direction, while the easy axis of the film under the tensile strain lies along the in-plane direction parallel to the [1-10]_GSO one. The results demonstrate that the electrical and magnetic properties of the tetragonal SRO thin films are closely related to the RuO₆ octahedral deformations due to the substrate-induced strain.