Hiroshi Kageyama

During the last century, inorganic oxide compounds laid foundations for materials synthesis, characterization, and technology translation by adding new functions into devices previously dominated by main-group element semiconductor compounds. Today, compounds with multiple anions beyond the single-oxide ion, such as oxyhalides and oxyhydrides, offer a new materials platform from which superior functionality may arise. Here we review the recent progress, status, and future prospects and challenge

Magnetic susceptibility, Cu NQR, and high-filed magnetization have been measured in polycrystalline $\mathrm{SrCu}{}_{2}(\mathrm{BO}{}_{3}{)}_{2}$ having a two-dimensional (2D) orthogonal network of Cu dimers. This cuprate provides a new class of 2D spin-gap system $(\ensuremath{\Delta}\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}30\mathrm{K})$ in which the ground state can be solved ``exactly.'' Furthermore, in the magnetization, two plateaus corresponding to $\frac{1}{4}$ and $\frac{1}{8

Magnetization measurements on the one-dimensional oxide Ca 3 Co 2 O 6 having a triangular net of Co 2 O 6 chains have been carried out both in static and pulsed high magnetic fields. The M / H vs. T curve obeys the Curie-Weiss law at high temperatures. Below 25 K, however, M / H increases abruptly, and a plateau is observed at 1/3 of the full moment in the M - H curve, suggesting a ferrimagnetic state of the ferromagnetic chains due to the antiferromagnetic interchain interaction. At low H , thi

We performed inelastic neutron scattering on the 2D Shastry-Sutherland system SrCu2(11BO3)2 with an exact dimer ground state. Three energy levels at around 3, 5, and 9 meV were observed at 1.7 K. The lowest excitation at 3.0 meV is almost dispersionless with a bandwidth of 0.2 meV at most, showing a significant constraint on a single-triplet hopping owing to the orthogonality of the neighboring dimers. In contrast, the correlated two-triplet excitations at 5 meV exhibit a more dispersive behavio

Magnetic properties of Ca 3 Co 2 O 6 with ferromagnetic Ising chains have been studied using oriented sample along the chain direction. From the extremely anisotropic behavior in its magnetization at low temperatures and in the temperature dependence of magnetic susceptibility, it is suggested that an octahedral Co 3+ is nonmagnetic, whereas a trigonal prismatic Co 3+ has a fictitious spin S '=1 with large single-ion anisotropy ( D ∼-25 K, g // ∼4). At low temperatures below 5 K, multisteps are

Abstract Mixed-anion compounds, in which multiple anions such as O2−, N3−, and H− are contained in the same compound, have recently attracted attention. Because mixed-anion compounds have a unique crystal structure with multiple anions coordinated to cations, materials with fundamentally new and innovative functions are expected to be developed for various chemistry and physics applications, including catalysts, batteries, and superconductors. In this Account, recent progress in the development

Reduction with CaH2 of double-layered perovskite Sr3Fe2O7 yielded novel two-legged S=2 ladder compound Sr3Fe2O5. Together with the synthesis of SrFeO2, this opens up new avenues for solid-state chemistry and physics of a series of n-legged ladders Srn+1FenO2n+1. The picture illustrates the structural transformation from FeO6 octahedra in Sr3Fe2O7 to FeO4 squares in Sr3Fe2O5, which occurs via intermediate Sr3Fe2O6 (Sr blue, O red, Fe yellow). Spin ladders, which conceptually are unidirectional se

We report a novel oxyhydride SrCrO2H directly synthesized by a high-pressure high-temperature method. Powder neutron and synchrotron X-ray diffraction revealed that this compound adopts the ideal cubic perovskite structure (Pm3̄m) with O(2-)/H(-) disorder. Surprisingly, despite the non-bonding nature between Cr 3d t(2g) orbitals and the H 1s orbital, it exhibits G-type spin ordering at T(N)≈380 K, which is higher than that of RCrO3 (R=rare earth) and any chromium oxides. The enhanced T(N) in SrC

We report on the magnetic properties of double-layered perovskite (CuCl)LaNb 2 O 7 with a square lattice of S =1/2 Cu 2+ ions, prepared by topotactic ion-exchange reactions. Magnetic susceptibility exhibits a thermal-activated behavior, and the analysis of the data suggests competing ferro- and antiferromagnetic exchanges for first- and second-nearest-neighbor bonds, respectively. Neutron scattering experiments provide explicit evidence for a spin-singlet ground state with an energy gap of 2.3 m

The development of semiconductors with narrow band gap and high stability is crucial for achieving solar to chemical energy conversion. Compounds with iodine, which has a high polarizability, have attracted attention because of their narrow band gap and long carrier lifetime, as typified by halide perovskite solar cells; however, they have been regarded as unsuitable for harsh photocatalytic water splitting because iodine is prone to self-oxidation. Here, we demonstrate that Ba₂Bi<sub