Jahn-Teller Switching of a Redox-Active Nickel(III) Center in a Homoleptic Thiolato Metalloligand Environment.

Treatment of nickel(II) nitrate with the iridium(III) metalloligand -[Ir(apt)] (apt = 3-aminopropanethiolate) gave the trinuclear complex [Ni{Ir(apt)}](NO) ([](NO)), in which the nickel center has a formal oxidation state of +III. Chemical or electrochemical oxidation and reduction of [](NO) generated the corresponding trinuclear complexes [Ni{Ir(apt)}](NO) ([](NO)) and [Ni{Ir(apt)}](NO) ([](NO)) with one-electron oxidated and reduced states, respectively. Single-crystal X-ray crystallography revealed that the nickel center in [](NO) is situated in a highly distorted octahedron due to Jahn-Teller effect, while the nickel center in each of [](NO) and [](NO) adopts a normal octahedral geometry.

Effect of Anisotropic Hybridization in YbAlB_{4} Probed by Linear Dichroism in Core-Level Hard X-Ray Photoemission Spectroscopy.

We have probed the crystalline electric-field ground states of pure |J=7/2,J_{z}=±5/2⟩ as well as the anisotropic c-f hybridization in both valence fluctuating systems α- and β-YbAlB_{4} by linear polarization dependence of angle-resolved core level photoemission spectroscopy. Interestingly, the small but distinct difference between α- and β-YbAlB_{4} was found in the polar angle dependence of linear dichroism, indicating the difference in the anisotropy of c-f hybridization, which may be a key to understanding a heavy Fermi liquid state in α-YbAlB_{4} and a quantum critical state in β-YbAlB_{4}.

Heterogeneous catalase-like activity of gold(i)-cobalt(iii) metallosupramolecular ionic crystals.

Unique heterogeneous catalase-like activity was observed for metallosupramolecular ionic crystals [AuCo(dppe)(d-pen)]X ([]X ; dppe = 1,2-bis(diphenylphosphino)ethane; d-pen = d-penicillaminate; X = (Cl), (ClO), (NO) or SO) consisting of AuCo complex cations, [], and inorganic anions, X or X. Treatment of the ionic crystals with an aqueous HO solution led to considerable O evolution with a high turnover frequency of 1.4 × 10 h for the heterogeneous cobalt complexes, which was dependent on their size and shape as well as the arrangement of cationic and anionic species.

Polarized hard X-ray photoemission system with micro-positioning technique for probing ground-state symmetry of strongly correlated materials.

An angle-resolved linearly polarized hard X-ray photoemission spectroscopy (HAXPES) system has been developed to study the ground-state symmetry of strongly correlated materials. The linear polarization of the incoming X-ray beam is switched by a transmission-type phase retarder composed of two diamond (100) crystals. The best value of the degree of linear polarization was found to be -0.

Soft X-ray angle-resolved photoemission with micro-positioning techniques for metallic V₂O₃.

Soft X-ray angle-resolved photoemission has been performed for metallic V2O3. By combining a microfocus beam (40 µm × 65 µm) and micro-positioning techniques with a long-working-distance microscope, it has been possible to observe band dispersions from tiny cleavage surfaces with a typical size of several tens of µm. The photoemission spectra show a clear position dependence, reflecting the morphology of the cleaved sample surface.

Development of a soft X-ray angle-resolved photoemission system applicable to 100 µm crystals.

A system for angle-resolved photoemission spectroscopy (ARPES) of small single crystals with sizes down to 100 µm has been developed. Soft X-ray synchrotron radiation with a spot size of ∼40 µm × 65 µm at the sample position is used for the excitation. Using this system an ARPES measurement has been performed on a Si crystal of size 120 µm × 100 µm × 80 µm.

In situ positioning of a few hundred micrometer-sized cleaved surfaces for soft-x-ray angle-resolved photoemission spectroscopy by use of an optical microscope.

A method to position samples with small cleaved regions has been developed to be applied to the angle-resolved photoemission spectroscopy (ARPES) which uses soft-x-ray synchrotron radiation focused down to 160 x 180 microm(2). A long-working-distance optical microscope is used for the sample observation. A selected region on a sample can be optimally set at the position of measurements, which is realized by the spatial resolution of the photoelectron analyzer.

Band Jahn-Teller instability and formation of valence bond solid in a mixed-valent spinel oxide LiRh2O4.

We have synthesized a new spinel oxide LiRh2O4 with a mixed-valent configuration of Rh3+ and Rh4+. At room temperature, it is a paramagnetic metal, but on cooling, a metal-insulator transition occurs and a valence bond solid state is formed below 170 K. We argue that the formation of valence bond solid is promoted by a band Jahn-Teller transition at 230 K and the resultant confinement of t_{2g} holes within the xy band.

High-resolution photoelectron spectroscopy of Heusler-type Fe(2)VAl alloy.

The electronic structure of Heusler-type Fe(2)VAl has been studied by high-resolution photoelectron spectroscopy with the excitation photon energy hnu ranging from 21.2 eV (the He I laboratory light source) to 904 eV (the soft X-ray synchrotron light source) for clean surfaces prepared by scraping or fracturing polycrystalline and single crystalline specimens. Photoelectron spectra recorded for the fractured surfaces show a 10 eV-wide valence band with fine structures and a clear decrease in the intensity towards the Fermi level E(F), while a high intensity at E(F) and no fine structures are observed for the scraped surface.