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Studies on magnetic oxyhydrides have been almost limited to perovskite-based lattices with corner-sharing octahedra with a M−H−M (M: transition metal) angle of θ ∼ 180°. Using a high-pressure method, we prepared BaCrO 2 H with a 6H-type hexagonal perovskite structure with corner-and face-sharing octahedra, offering a unique opportunity to investigate magnetic interactions based on a θ ∼ 90°case. Neutron diffraction for BaCrO 2 H revealed an antiferromagnetic (AFM) order at T N ∼ 375 K, which is higher than ∼240 K in BaCrO 3−x F x . The relatively high T N of BaCrO 2 H can be explained by the preferred occupancy of H − at the face-sharing site that provides AFM superexchange in addition to AFM direct exchange interactions. First-principles calculations on BaCrO 2 H in comparison with BaCrO 2 F and BaMnO 3 further reveal that the direct Cr−Cr interaction is significantly enhanced by shortening the Cr−Cr distance due to the covalent nature of H − . This study provides a useful strategy for the extensive control of magnetic interactions by exploiting the difference in the covalency of multiple anions.

SrMoO3 is a promising material for its excellent electrical conductivity, but growing high-quality thin films remains a challenge. Here we synthesized epitaxial films of SrMoO3 using molecular beam epitaxy (MBE) technique under low oxygen-flow rate. Introduction of SrTiO3 buffer layers of 4-8 unit cells between the film and the (001)-oriented SrTiO3 or KTaO3 substrate was crucial to remove impurities and/or roughness of the film surface. The obtained film shows improved electrical conductivities as compared with films obtained by other techniques. The high quality of the SrMoO3 film is also verified by angle resolved photoemission spectroscopy (ARPES) measurements showing a clear Fermi surfaces.

We report the epitaxial thin-film synthesis of SrCu 3 O 4 with infinitely stacked Cu 3 O 4 layers composed of edge-sharing CuO 4 square planes, using molecular-beam epitaxy. Experimental and theoretical characterizations showed that this material is a metastable phase that can exist by applying tensile biaxial strain from the (001)-SrTiO 3 substrate. SrCu 3 O 4 shows an insulating electrical resistivity in accordance with the Cu 2+ valence state revealed by X-ray photoelectron spectroscopy. First-principles calculations also indicated that the unoccupied d 3z 2 −r 2 band becomes substantially stabilized owing to the absence of apical anions, in contrast to A 2 Cu 3 O 4 Cl 2 (A = Sr, Ba) with an A 2 Cl 2 block layer and therefore a trans-CuO 4 Cl 2 octahedron. These results suggest that SrCu 3 O 4 is a suitable parent material for electron-doped superconductivity based on the Cu 3 O 4 plane.

A double-layered perovskite oxide Sr3Mo2O7 is considered a "hidden ladder" system with wide and narrow bands near the Fermi level, for which high-Tc superconductivity is expected. However, the difficulty in synthesis, especially in the preparation of samples without oxygen deficiency, can hinder the observation of superconductivity. In this study, we constructed a double-layer SrMoO3 block through artificial superlattices with the insulating SrTiO3 block, (SrMoO3)m/(SrTiO3)t (m = 2, 4; t = 4). First-principles calculations for bilayered SrMoO3 (m = 2) exhibit a wide-narrow band structure near the Fermi level, which bears a close resemblance to Sr3Mo2O7. The dispersion along the kz direction is strongly suppressed by increasing the number of the SrTiO3 layers, t. However, no superconductivity is observed down to 0.1 K. We discuss the absence of the superconductivity for the present films on the basis of results of scanning transmission electron microscopy and band structure calculations.