Hyomen Kagaku
Online ISSN : 1881-4743
Print ISSN : 0388-5321
ISSN-L : 0388-5321
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Preface
Special Issue: Novel Electronic States and Atomic Structures at Oxide Surfaces and Interfaces
  • Hiroshi KUMIGASHIRA
    Type: Current Topic
    2017 Volume 38 Issue 12 Pages 596-601
    Published: December 10, 2017
    Released: December 21, 2017
    JOURNALS FREE ACCESS
    The quantum confinement of strongly correlated electrons in artificial structures has heralded the possibility of creating the novel quantum materials with extraordinary physical properties. By optimally combining sophisticated oxide growth techniques and advanced analysis techniques using synchrotron radiation, we have designed and controlled the novel quantum phenomena emerging in oxide artificial structures. The observed metallic quantum-well states in digitally controlled ultrathin films of strongly correlated oxide SrVO3 exhibit characteristic features reflecting their strongly correlated nature. Furthermore, the structural controllability of the quantum-well structures enables us to investigate how the electronic structure changes as a function of dimensionality. The present study demonstrates that the quantum-well structure of strongly correlated oxides will provide a new strategy for both investigating the behavior of correlated electrons under varying interactions among their spin, charge, and orbital degrees of freedom and for manipulating novel quantum phenomena in reduced dimensions.
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  • Hiroki WADATI, Kohei YAMAMOTO
    Type: Current Topic
    2017 Volume 38 Issue 12 Pages 602-607
    Published: December 10, 2017
    Released: December 21, 2017
    JOURNALS FREE ACCESS

    Observing ordered states in transition-metal oxides has been one of the most important topics in contemporary condensed-matter physics because ordering phenomena is directly related to anomalous physical properties such as superconductivity, colossal magnetoresistance, multiferroicity, and metal-insulator transition. Resonant soft x-ray diffraction has emerged as a new experimental tool for investigating spin ordering, and is especially suitable for studying thin films. Here we show how we have successfully observed charge/spin ordered states in transition-metal-oxide thin films by combining hard and soft x-ray diffraction.

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  • Kanta ASAKAWA, Taizo KAWAUCHI, Katsuyuki FUKUTANI
    Type: Current Topic
    2017 Volume 38 Issue 12 Pages 608-613
    Published: December 10, 2017
    Released: December 21, 2017
    JOURNALS FREE ACCESS

    The magnetic and electronic structures of the Fe3O4(111) surface were investigated by conversion electron Mössbauer spectroscopy (CEMS) and ultraviolet photoemission spectroscopy (UPS), respectively. The CEMS results indicated that the Fe3O4(111) surface is covered by closure domains, and that the magnetization direction of the Fe(B) site is more parallel to the surface than the non-perpendicular easy axes while that of the Fe(A) site corresponds to the easy exes. This indicates that the spins of the Fe(A) and Fe(B) sites are non-collinear near the surface. By using UPS, we have discovered that the H atom adsorption on the Fe(A)-terminated Fe3O4(111) surface reduces the work function but does not induce charge transfer. On the O2-exposed Fe(A)-terminated Fe3O4(111) surface, on the other hand, H adsorption increases the Fe(B) t2g derived peak in the UPS spectrum and decreases the work function. This indicates that, on the O2-exposed Fe(A)-terminated Fe3O4(111) surface, H atoms adsorb as cations and dope electrons to the Fe(B) t2g orbital.

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  • Jobu MATSUNO
    Type: Current Topic
    2017 Volume 38 Issue 12 Pages 614-619
    Published: December 10, 2017
    Released: December 21, 2017
    JOURNALS FREE ACCESS
    Spin-orbit interaction in solids can be utilized for controlling spin-dependent transport phenomena. To realize them, we focus on thin films and interfaces of iridium (Ir) oxides since electron conduction there is dominated by 5d electrons with strong spin-orbit interaction. The first example is the inverse spin Hall effect, which converts a spin current into an electric voltage. The performance of IrO2 as a spin-current detector is better than those of noble metals. The second is the topological Hall effect originating from magnetic skyrmions. The epitaxial bilayers consisting of SrRuO3 and SrIrO3 enable us to generate skyrmions through artificially broken inversion symmetry at the interfaces. These results can be a step toward future spintronics.
    Editor’s picks

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  • Tetsuroh SHIRASAWA, Wolfgang VOEGELI, Etsuo ARAKAWA, Chika KAMEZAWA, T ...
    Type: Current Topic
    2017 Volume 38 Issue 12 Pages 620-625
    Published: December 10, 2017
    Released: December 21, 2017
    JOURNALS FREE ACCESS

    A hydrophobic TiO2 surface can be converted to a hydrophilic one by UV light irradiation. This phenomenon was discovered more than 20 years ago and has been used in a variety of coating applications. However, the mechanism is not well understood. In particular, it is still not clear whether and how the surface structure is involved. We studied the possible structural change of the rutile-TiO2(110) surface by using X-ray crystal truncation rod (CTR) scattering. We demonstrated the occurrence of a surface structural change during the photoirradiation by using the high-speed CTR scattering profile measurement in a wavelength dispersive mode. We determined the structure of the hydrophobic (non-irradiated) and hydrophilic (photoirradiated) surfaces based on static CTR data, and proposed a possible mechanism of the water wettability transition.

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  • Masaaki HIRAYAMA
    Type: Current Topic
    2017 Volume 38 Issue 12 Pages 626-631
    Published: December 10, 2017
    Released: December 21, 2017
    JOURNALS FREE ACCESS

    Gaining a thorough understanding of the electrochemical interface in lithium ion batteries is essential for the development of a common strategy for the material design. This paper presents the interfacial reaction analyses between intercalation electrodes and organic electrolytes using an epitaxial-film model electrode and in situ surface scattering techniques which directly detect crystal structures in 10 nm-regions from the top of the electrode surface. The crystal structures of the intercalation electrodes drastically change in the surface regions when soaked to the electrolyte and are reconstructed during the initial electrochemical reaction. The reconstructed surface regions have a pronounced effect on the power characteristics and the stability at the subsequent electrochemical cycles.

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