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Perovskite chromate SrCrO3 containing Cr4+ ions shows anomalous electronic states and physical properties, which are believed to be related to the bonding instability, but this has not been confirmed directly in experiments up to now. In order to address this issue, the crystal structure and electronic structure of SrCrO3 are investigated by using transmission electron microscopy and first-principles calculations. The results demonstrate that there is no fourfold rotational symmetry in the selected area electron diffraction patterns along the three main zone axes of SrCrO3, which is inconsistent with an expected cubic structure. Moreover, the orientation-dependent electron energy-loss spectra demonstrate a clear correlation between the dissimilar spectra and the anisotropic effects derived from the crystal structure, and first-principles calculations support the experimental results. All this strongly supports the bonding instability of ambient pressure and temperature phase of SrCrO3 and highlights the important influence of bonding fluctuation on its electronic structure and transport properties. The influence of the core-hole effect and Hubbard potential on the theoretical spectra is further investigated. [ABSTRACT FROM AUTHOR]

With the reduction in dimensions, interesting phenomena such as charge density waves and superconductivity emerge in AMn6Bi5 (A = Na, K, Rb, Cs) quasi-one-dimensional (quasi-1D) materials. Here, we report a high-quality Mn6Bi5 single crystal induced by the high-energy focus ion beam, which owns a quasi-1D crystal structure with infinite [Mn6Bi5]∞ chains. We optimize that the structure of Mn6Bi5 using density functional theory and characterize it using scanning transmission electron microscopy, and the rotation behavior of [Mn6Bi5]∞ chains is predicted and confirmed. We illustrate the quasi-1D nature of Mn6Bi5 by the density of states and band structure calculations and predict the anisotropic resistivity. Through comparing the Fermi surfaces of Mn6Bi5 and KMn6Bi5, we point out the tendency of the transition from quasi-1D to 3D crystal in Mn6Bi5. We observe and explain the apparent blueshift in the bulk plasmon peak in Mn6Bi5 and point out the reason for forming the shoulder peak in the Mn L3 peak. [ABSTRACT FROM AUTHOR]

The two-dimensional hole gas (2DHG) at the polar LaAlO3/SrTiO3 interface remains elusive. Different from isostructural perovskite-type interfaces, the spinel/perovskite heterointerface of γ-Al2O3/SrTiO3 (GAO/STO) enables us to control interfacial states with sub-unit-cell precision. Herein, we present the epitaxial growth of fractionally doped GAO/STO heterointerfaces, where GAO is precisely doped on the scale of 1/4-unit-cell (0.2 nm) by ferromagnetic Fe3O4 and nonmagnetic ZnO atomic layers. Notably, the conduction of the engineered interfaces depends critically on the position of the dopant, where a coexistence of electron and hole conduction is measured at even sublayer-doped GAO/STO interfaces. First-principles density functional theory calculations indicate that electron conductivity is from the interfacial TiO2 layers of the STO substrate, while the hole conductivity is from the Zn-doped GAO film. The presence of hole conduction can be explained from the alternating structural feature of a doped layer without oxygen vacancies. This work sheds additional insight on the emergence of 2DHG at oxide interfaces and provides opportunities for atomically engineered oxide interfaces with non-isostructural layers. [ABSTRACT FROM AUTHOR]

Transport of intensity equation (TIE) has been applied to process the simulated and experimental images of the magnetic hard nanobubbles, which were acquired using a Lorentz transmission electron microscope. Systematic studies demonstrated that the processing parameter in TIE can modulate the features of the retrieved magnetization and induce the bi-spiral structures which may be identified as bi-skyrmions. [ABSTRACT FROM AUTHOR]

The interfacial coupling between electron correlated complex oxides opens a promising avenue for achieving new forms of magnetism that arises as a consequence of charge transfer, orbital reconstruction and symmetry-breaking. Herein we reported a distinct magnetic structure in La2/3Sr1/3MnO3 (LSMO) film sandwiched between La1/2Sr1/2CoO2.5+δ (LSCO) bilayer grown on (001)-oriented SrTiO3 substrates. It is found that the LSMO layer of heterostructure contains two independent components that are respectively free layer (free-LSMO) and coupled layer with LSCO (coupled-LSMO). The easy axis of the free-LSMO is in-plane, while it is out-of-plane directed for the coupled-LSMO layer. The thickness of these two parts in the LSMO layer are 4uc and 12uc respectively. This is in sharp contrast to the single LSMO layer on STO, for which the easy axis is always in film plane. Different from LSMO, the easy axis of LSCO is in-plane and is ferromagnetically coupled with LSMO. This distinct magnetic structure could be ascribed to orbital reconstruction due to symmetry-mismatch at interfaces. [ABSTRACT FROM AUTHOR]

Among transition-metal nitrides, the mononitride γ-MoN with a rock-salt structure has drawn particular attention because it has been predicted to possess excellent mechanical and electronic properties, especially the high superconducting temperature around 30 K. However, synthesis of bulk γ-MoNx with the nitrogen concentration, x, more than 0.5 is still challenging, leading to contradictions on its phase stability and properties. In this work, we formulated a high-pressure synthesis reaction for the formation of single-crystal γ-MoNx with a remarkably high nitrogen concentration value of x ≈ 0.67. This nitride possesses a high asymptotic hardness of ∼24 GPa, which is so far the second hardest among metal nitrides. Impressively, the expected superconductivity is absent in the as-synthesized product. We further performed density functional theory calculations to clarify the structural stability and the absence of superconductivity in stoichiometric γ-MoN. We find that the ground state of γ-MoN is theoretically explored to be a Mott insulator with an antiferromagnetic phase, while a paramagnetic configuration is adopted at the ambient conditions. Such magnetic properties would explain the structural stability and the absence of superconductivity in the as-synthesized γ-MoNx with a high nitrogen concentration. [ABSTRACT FROM AUTHOR]

The magnetic properties of hexagonal Ba(Ti1-xMnx)O3 (x = 1/9, 1/6) samples specifically treated under different thermal conditions are investigated. A magnetic transformation from paramagnetism of as-grown samples to weak ferromagnetism of post-annealed samples is observed at room temperature. Associated with the structural modulation characteristics and dielectric behaviors, our experimental results reveal that the high-temperature ferromagnetism in Mn-doped hexagonal BaTiO3 derives from RIII types of antiphase domain boundaries. Spin glass transitions are observed at Tsg = 48 K and 44 K in the densely doped as-grown and post-annealed samples, respectively, but the transitions are not intrinsic properties of the hexagonal phases. [ABSTRACT FROM AUTHOR]

Film of Fe3O4 was prepared with laser molecular beam epitaxy deposition on a Si substrate with a native SiO2 layer. When the temperature is increased above 250 K, the resistance drops rapidly because the conduction path starts to switch from the Fe3O4 film to the inversion layer underneath the SiO2 via thermally assisted tunneling. A greatly magnified low field negative magnetoresistance of Fe3O4 is observed at 280 K. The effect is similar to a metal-oxide-semiconductor field-effect transistor. The magnetoresistance becomes positive with further increase in the magnetic field due to the Lorentz force and other effects on the carriers in the inversion layer. [ABSTRACT FROM AUTHOR]