Kaneko, Koji; Frontzek, M. D.*; Matsuda, Masaaki*; Nakao, Akiko*; Munakata, Koji*; Ohara, Takashi; Kakihana, Masashi*; Haga, Yoshinori; Hedo, Masato*; Nakama, Takao*; et al.
Journal of the Physical Society of Japan, 88, p.013702_1 - 013702_5, 2019/01
Magnetic transitions in chiral antiferromagnet EuPtSi were investigated by means of single crystal neutron diffraction. In the ground state, magnetic peaks emerge at positions represented by =. Upon heating, an additional magnetic peak splitting around 2.5 K was uncovered, indicating a presence of a first-order transition with =. An half-polarized neutron scattering for polarization parallel to Q reveled that polarization antiparallel to Q has stronger intensity in both magnetic phases. This feature clarifies single chiral character of helical structure with moments normal to the ordering vector in both ordered states. Under vertical magnetic field along [1,1,1] in the phase, magnetic peaks form hexagonal patterns in the equatorial scattering plane around nuclear. An ordering vector of the -phase has the similar size in the periodicity to , and could be a hallmark of a formation of skyrmion lattice in EuPtSi.
Okuchi, Takuo*; Tomioka, Naotaka*; Purevjav, N.*; Shibata, Kaoru
Journal of Applied Crystallography, 51, p.1564 - 1570, 2018/12
It is demonstrated that quasielastic neutron scattering (QENS) is a novel and effective method to analyse atomic scale hydrogen transport processes occurring within a mineral crystal lattice. The method was previously characterized as sensitive for analysing the transport frequency and distance of highly diffusive hydrogen atoms or water molecules in condensed matter. Here are shown the results of its application to analyse the transport of much slower hydrogen atoms which are bonded into a crystal lattice as hydroxyls. Two types of hydrogen transport process were observed in brucite, Mg(OH) : a jump within a single two-dimensional layer of the hydrogen lattice and a jump into the next nearest layer of it. These transport processes observed within the prototypical structure of brucite have direct implications for hydrogen transport phenomena occurring within various types of oxides and minerals having layered structures.
Kishi, Hirofumi*; Sakamoto, Tomokazu*; Asazawa, Koichiro*; Yamaguchi, Susumu*; Kato, Takeshi*; Zulevi, B.*; Serov, A.*; Artyushkova, K.*; Atanassov, P.*; Matsumura, Daiju; et al.
Nanomaterials, 8(12), p.965_1 - 965_13, 2018/12
Platinum group metal-free catalysts based on transition metal-nitrogen-carbon nanomaterials have been studied by a combination of in situ X-ray spectroscopy techniques, high-resolution transmission electron microscope, Mssbauer spectroscopy, electrochemical methods and density functional theory. Fe-N-C oxygen reduction reaction electrocatalysts were synthesized by varying several synthetic parameters to obtain nanomaterials with different composition and morphology. Associated with Fe-N motive and the presence of Fe metallic particles in the electrocatalysts showed the clear differences in the variation of composition; processing and treatment conditions of sacrificial support method. From the results of material characterization; catalytic activity and theoretical studies; Fe metallic particles (coated with carbon) are main contributors into the HO generation.
Nakajima, Kenji; Kajimoto, Ryoichi
Physica B; Condensed Matter, 551, p.142 - 145, 2018/12
We will report on magnetic excitations in lightly oxygen doped lanthanum nickel oxide, LaNiO. By introducing slightly excessive oxygen atoms in the system, magnetic excitations in LaNiO drastically changes its picture. In lower energy region, spin-wave stiffness strongly suppressed. On the other hand, in the higher energy region, spin-wave dispersion curve is almost same as in the stoichiometric system, while excitations show considerable broadening. Alternation of the character of the excitations by changing energy is also reported in hole doped cuprates and cobalates. We consider that this behavior is one of key clues to understand magnetism and transport properties in carrier doped layered transition metal oxides. We investigated detail of magnetic excitations in two different lightly doped systems, LaNiO and LaNiO in wide momentum and energy transfer space by using time-of-flight spectrometers at J-PARC. Observed doping effects in magnetic excitations will be discussed by comparing them to those reported in other related layered transition metal oxides.
Nakamura, Mitsutaka; Kambara, Wataru*; Iida, Kazuki*; Kajimoto, Ryoichi; Kamazawa, Kazuya*; Ikeuchi, Kazuhiko*; Ishikado, Motoyuki*; Aoyama, Kazuhiro*
Physica B; Condensed Matter, 551, p.480 - 483, 2018/12
Recently there has been an increasing need for inelastic neutron scattering experiments under some special environments such as magnetic fields, pressure and high temperatures. In order to obtain high quality data, the unnecessary scattering caused by sample environmental apparatus should be suppressed as much as possible. We have developed an oscillating radial collimator with a view to satisfying users' needs, which is specialized for the Fermi chopper spectrometer 4SEASONS at J-PARC.4SEASONS provides relatively high incident energies, and thus we chose hydrogen free metal sheets as the collimator blades. The control system of this oscillating radial collimator enables us to flexibly tune the oscillating pattern, such as the oscillating speed and oscillating angle. In this presentation, we report the performances and remaining issues of the newly developed oscillating radial collimator for 4SEASONS.
Nakamura, Mitsutaka; Kikuchi, Tatsuya*; Kamazawa, Kazuya*; Kawakita, Yukinobu
Physica B; Condensed Matter, 551, p.351 - 354, 2018/12
The dynamic structure function in real space G() is deduced from the dynamical structure factor S() which can be obtained from inelastic neutron scattering measurement. In this study, we applied the G() analysis to NaI which is a typical alkali halide crystal. The optic and acoustic phonons of NaI are widely separated in energy because the difference in mass between the constituent atoms is large. These characteristic properties certainly help us to evaluate the G() features associated with the phonon modes. We measured the S() for NaI powder using the Fermi chopper spectrometer 4SEASONS at J-PARC, and converted S() into G() by newly developed software which utilizes the maximum entropy method. Our analysis clearly demonstrated the G() of TO mode oscillates out of phase with that of LA mode, which is physically reasonable. Further analyses will be given in the presentation.
Kai, Tetsuya; Sato, Setsuo*; Hiroi, Kosuke; Su, Y.; Segawa, Mariko; Parker, J. D.*; Matsumoto, Yoshihiro*; Hayashida, Hirotoshi*; Shinohara, Takenao; Oikawa, Kenichi; et al.
Physica B; Condensed Matter, 551, p.496 - 500, 2018/12
The 2012 model lithium-6 time-analyzer neutron detector (LiTA12) system, based on a lithium glass scintillator and multi-anode photomultiplier tube, has the highest neutron efficiency among the detectors for pulsed neutron imaging together with a flexibility of the efficiency by changing the thickness of the lithium glass. The authors expect this detector system could become a main detector system for the energy-resolved neutron imaging system, RADEN, at J-PARC, and have started evaluation of the LiTA12 system. For example, spatial resolution for resonance absorption imaging was evaluated by using a line-pair pattern made by 3 micro meter thick gold on a quartz plate. Less than 1 mm width line pairs were resolved at an 8 Mcps neutron counting rate and around 5 eV neutron energy.
Li, S.*; Toyoda, Masayuki*; Kobayashi, Yoshiaki*; Ito, Masayuki*; Ikeuchi, Kazuhiko*; Yoneda, Yasuhiro; Otani, Akira*; Matsumura, Daiju; Asano, Shun*; Mizuki, Junichiro*; et al.
Physica C, 555, p.45 - 53, 2018/12
-dependence of local distortions in BaFeAs and LiFeAs by X-ray PDF and XAFS methods. Although PDF data exhibit anomaly at the structure transition temperature, EXAFS data exhibit no anomaly. Data supporting the local orthorhombicity at 300 K in the tetragonal phase for BaFeAs. Arguments on the origins of the 4-fold symmetry breaking in the ground average structure of the tetragonal phase.
Hayashi, Makoto*; Root, J. H.*; Rogge, R. B.*; Xu, P. G.
Quantum Beam Science (Internet), 2(4), p.21_1 - 21_16, 2018/12
The rolled joint of pressure tube, consisting of three axial symmetric parts, modified SUS403 stainless steel, Zr-2.5Nb pressure tube and Inconel-718, has been examined by neutron diffraction for residual stresses. It was heat treated at 350C for 30, 130 and 635 hours to simulate the thermal aging of the rolled joint over the lifetime of the advanced thermal reactor at 288C for 1, 5 and 30 years. The crystal lattice strains at various locations in the rolled joint before and after the aging treatments were measured by neutron diffraction and the residual stress distribution in the rolled joint was evaluated by using the Kroner elastic model and the generalized Hooke's law. In the crimp region of the rolled joint, it was found that the aging treatment had weak effect on the residual stresses in the Inconel and the SUS403. In the non-aged Zr-2.5Nb, the highest residual stresses were found near its interface with the SUS430. In the Zr-2.5Nb in the crimp region near its interface with the SUS430, the average compressive axial stress was -440 MPa, having no evident change during the long-time aging. In the Zr-2.5Nb outside closest to the crimp region, the tensile axial and hoop stresses were relieved during the 30 hours aging. The hoop stresses in the crimp region evolved from an average tensile stress of 80 MPa to an average compressive stress of 230 MPa after the 635 hours aging, suggesting that the rolled joint had a good long-term sealing ability against the leakage of high temperature water.
Kakitani, Kenta*; Kimata, Tetsuya*; Yamaki, Tetsuya*; Yamamoto, Shunya*; Matsumura, Daiju; Taguchi, Tomitsugu*; Terai, Takayuki*
Radiation Physics and Chemistry, 153, p.152 - 155, 2018/12
The chemical state and local structure of 2.6-nm-sized platinum (Pt) nanoparticles on an ion-irradiated glassy carbon (GC) substrate were investigated by X-ray absorption fine structure measurements. The partial oxidation of the Pt nanoparticles was confirmed by the peak intensity in the near-edge region of the absorption spectrum. The analysis of the extended region revealed a higher coordination number and shorter bond length of Pt-Pt compared to those of the Pt nanoparticles on the non-ion-irradiated GC. Thus, Pt nanoparticles on the ionirradiated GC substrate were found to hold a rigid metallic coordination during the oxidation.
Shiki, 41, P. 4, 2018/12
This article described the detailed structure of a nanogel formed by self-association of polysaccharides determined by contrast variation small-angle neutron scattering.
Igawa, Naoki; Kodama, Katsuaki; Taguchi, Tomitsugu*; Yoshida, Yukihiko*; Matsukawa, Takeshi*; Hoshikawa, Akinori*; Ishigaki, Toru*
Transactions of the Materials Research Society of Japan, 43(6), p.329 - 332, 2018/12
For the understanding of the crystal structural effect on the electrical properties, the local disorder in BaSnInO which is one of the excellent proton conductors for solid oxide fuel cells was estimated by using the Atomic Pair Distribution Function (PDF) analysis method with the neutron diffraction. The local structure is almost the same as the average structure which was estimated by the Rietveld analysis using the cubic crystal structure (space group, ) in the atomic distance range of 6. The PDF profile was fitted better using the tetragonal crystal structure with the space group of 4/ than those with in the range 6. Those results indicate the presence of the local disorder in the lattice. In this work, the relationship between the average and local structures of BaSnInO will be discussed.
Hamon, 28(4), p.204 - 207, 2018/11
A Neutron guide is one of the devices to transport neutron beam for long distance without sacrificing much neutrons; therefore, it can supply neutrons to many experimental instruments distributed in a large experimental hall. Also, by using a curved guide, only the neutrons in a required energy range can be transported, and rays and fast neutrons can be effectively eliminated, therefore the signal to background ratio is improved. In addition, a neutron beam can be branched by applying curved guides. Neutron guides are also used to control the divergence angle and intensity of the neutron beam supplied to the neutron instrument.
Hamon, 28(4), p.208 - 211, 2018/11
Adequate shielding of neutrons and associated -rays is of importance from viewpoints of the radiation safety of researchers and good experimental data taking by reducing the background. This article introduces basics of neutron shielding, physics and suitable materials for neutron and -ray shielding, and an example of conceptual shielding design for the 1-MW spallation neutron source of J-PARC MLF.
Maruyama, Ryuji; Yamazaki, Dai; Soyama, Kazuhiko
JPS Conference Proceedings (Internet), 22, p.011011_1 - 011011_5, 2018/11
Neutron multilayer mirrors are one of the most important optical elements for neutron scattering experiments. Good interface quality in terms of sharpness and smoothness plays a critical role in determining the performance of optical elements. We have shown that a multilayer with a large vertical correlation length and small lateral correlation length effectively suppresses the diffuse scattering intensity. In this study, the effect of the interface roughness correlation on the neutron reflectivity of the multilayer mirror is investigated using the reflectivity calculation based on the distorted wave Born approximation.
Yoneda, Yasuhiro; Ohara, Koji*; Nagata, Hajime*
Japanese Journal of Applied Physics, 57(11S), p.11UB07_1 - 11UB07_6, 2018/11
Local structure analysis of KNbO, which is the parent compound for lead-free piezoelectric materials, have been performed by X-ray pair-distribution functions (PDF). The refinements of local structure in wide temperature ranges indicates that only the rhombohedral structure can describe the observed bond distributions within the unit cell. The rhombohedral distortion maintained locally in all four phases.
Metoki, Naoto; Haga, Yoshinori; Yamamoto, Etsuji; Matsuda, Masaaki*
Journal of the Physical Society of Japan, 87(11), p.114712_1 - 114712_9, 2018/11
The localized 5 states with 5 () configuration of U ion have been revealed in UPdAl. We found that the low-lying states are the same as PrPdAl flat orbitals with large are stabilized by a two-dimensional CEF potential in the unique crystal structure. The present study involves the valence crossover from tetravalent to trivalent in a series of AnPdAl, demonstrated by lattice and/or transport anomaly as well as many body effects in the vicinity of the boundary. The valence instability plays important role for the unusual heavy fermion superconductivity in NpPdAl.
Tamatsukuri, Hiromu*; Hiraka, Haruhiro*; Ikeuchi, Kazuhiko*; Iimura, Soshi*; Muraba, Yoshinori*; Nakamura, Mitsutaka; Sagayama, Hajime*; Yamaura, Junichi*; Murakami, Yoichi*; Kuramoto, Yoshio*; et al.
Physical Review B, 98(17), p.174415_1 - 174415_6, 2018/11
Magnetic excitations in a heavily electron-doped antiferromagnet, LaFeAsOD, have been investigated using powder inelastic neutron scattering. Unlike other parent compounds of the iron-based superconductors, the magnetic excitation gap in LaFeAsOD was not detected down to the lowest measured temperature of 4 K. This result can be understood as a result of quasi-isotropy within the ab plane, which is consistent with the band calculation result that the orbital plays the dominant role in the magnetism of LaFeAsOH. In addition, the intensities of the magnetic excitations in this phase are much stronger than those in nondoped LaFeAsO. Even in the paramagnetic phase, the magnetic excitation in LaFeAsOD persists. These results corroborate recent studies showing that the electron doping enhances the localized nature in this system.
Sekiguchi, Tetsuhiro; Yokoyama, Keiichi; Uozumi, Yuki*; Yano, Masahiro; Asaoka, Hidehito; Suzuki, Shinichi; Yaita, Tsuyoshi
Progress in Nuclear Science and Technology (Internet), 5, p.161 - 164, 2018/11
For nuclear transmutation of cesium-135 (Cs), which is long-lived fission product, we are developing selective absorbent which takes only Cs atom in, but does not CsI. In this study, absorbing property of Cs atom onto the surface of fullerene (C) film has been investigated using synchrotron-based angle-dependent X-ray photoelectron spectroscopy (XPS). The results were compared with those of CsI. It was found that Cs penetrates into C deep bulk. In contrast, CsI deposits on shallow surface. Furthermore, XPS spectra were measured as a function of Ar-sputtering time in order to know Cs concentration profiles in deep region. Results showed that Cs penetrates into deep region of several hundreds .
Kim, S. B.*; Lee, K.-H.*; Raj, M. S.*; Reeder, J. T.*; Koo, J.*; Hourlier-Fargette, A.*; Bandodkar, A. J.*; Won, S. M.*; Sekine, Yurina; Choi, J.*; et al.
Small, 14(45), p.1802876_1 - 1802876_9, 2018/11
Excretion of sweat from eccrine glands is a dynamic physiological process that varies with body position, activity level, and health status. Information content embodied in sweat rate and chemistry can be used to assess health status and athletic performance. This paper presents a thin, miniaturized, skin-interfaced microfluidic technology that includes a reusable, battery-free electronics module for measuring sweat conductivity and rate in real-time using wireless power from and data communication with capabilities in near field communications (NFC). Systematic studies of these combined microfluidic/electronic systems, accurate correlations of measurements performed with them to those of laboratory standard instrumentation, and field tests on human subjects establish the key operational features and their utility in sweat analytics.