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Journal Articles

Chemical-pressure-induced point defects enable low thermal conductivity for Mg$$_{2}$$Sn and Mg$$_{2}$$Si single crystals

Saito, Wataru*; Hayashi, Kei*; Huang, Z.*; Sugimoto, Kazuya*; Oyama, Kenji*; Happo, Naohisa*; Harada, Masahide; Oikawa, Kenichi; Inamura, Yasuhiro; Hayashi, Koichi*; et al.

ACS Applied Energy Materials (Internet), 4(5), p.5123 - 5131, 2021/05

 Times Cited Count:0 Percentile:0(Chemistry, Physical)

Journal Articles

Polarization analysis for small-angle neutron scattering with a $$^{3}$$He spin filter at a pulsed neutron source

Okudaira, Takuya; Ueda, Yuki; Hiroi, Kosuke; Motokawa, Ryuhei; Inamura, Yasuhiro; Takata, Shinichi; Oku, Takayuki; Suzuki, Junichi*; Takahashi, Shingo*; Endo, Hitoshi*; et al.

Journal of Applied Crystallography, 54(2), p.548 - 556, 2021/04

 Times Cited Count:0 Percentile:0.02(Chemistry, Multidisciplinary)

Neutron polarization analysis (NPA) for small-angle neutron scattering (SANS) experiments using a pulsed neutron source was successfully achieved by applying a $$^{3}$$He spin filter as a spin analyzer for the scattered neutrons. The $$^{3}$$He spin filter covers a sufficient solid angle for performing SANS experiments, and the relaxation time of the $$^{3}$$He polarization is sufficient for continuous use over a few days, thus reaching the typical duration required for a complete set of SANS experiments. Although accurate evaluation of the incoherent neutron scattering, which is predominantly attributable to hydrogen atoms in samples, is practically difficult using calculations based on the sample elemental composition, the developed NPA approach with consideration of the influence of multiple neutron scattering enabled reliable decomposition of the SANS intensity distribution into the coherent and incoherent scattering components. To date, NPA has not been well established as a standard technique for SANS experiments at pulsed neutron sources. This work is anticipated to greatly contribute to the accurate determination of the coherent neutron scattering component for scatterers in various types of organic sample systems in SANS experiments at J-PARC.

Journal Articles

Mode distribution analysis for superionic melt of CuI by coherent quasielastic neutron scattering

Kawakita, Yukinobu; Kikuchi, Tatsuya*; Tahara, Shuta*; Nakamura, Mitsutaka; Inamura, Yasuhiro; Maruyama, Kenji*; Yamauchi, Yasuhiro*; Kawamura, Seiko; Nakajima, Kenji

JPS Conference Proceedings (Internet), 33, p.011071_1 - 011071_6, 2021/03

CuI is a well-known superionic conductor in a high temperature solid phase where the mobile cations migrate between interstitial sites in the f.c.c. sublattice formed by iodine ions. Even in the molten state, it shows several features suggesting collective or cooperative ionic motion. MD results show that Cu diffuses much faster than I. The Cu-Cu partial structure factor have a FSDP which indicates a medium-range ordering of Cu ions. Moreover the Cu-Cu partial pair distribution deeply penetrates into the nearest neighboring Cu-I shell. To reveal origin such anomalous behaviors of molten CuI, we performed quaiselastic neutron scattering (QENS) by the disk-chopper spectrometer AMATERAS at MLF, J-PARC. To interpret the total dynamic structure factor obtained from coherent QENS, the mode distribution analysis was applied. It is found that the motion of iodine is a kind of fluctuating within an almost local area while Cu ions diffuse much faster than iodine ions.

Journal Articles

Recent update of AMATERAS; A Cold-neutron disk-chopper spectrometer

Nakajima, Kenji; Kawamura, Seiko; Kofu, Maiko; Murai, Naoki; Inamura, Yasuhiro; Kikuchi, Tatsuya*; Wakai, Daisuke*

JPS Conference Proceedings (Internet), 33, p.011089_1 - 011089_7, 2021/03

The recent update of AMATERAS, a cold-neutron disk-chopper spectrometer at Japan Proton Accelerator Research Complex (J-PARC), is reported. AMATERAS has been operating for a decade. Since 2017, some updates have been done or are underway, which include installing new detectors, replacing the vacuum system of the scattering chamber, and other works. We are also working on the re-investigation of the resolution function. Demonstration measurements were carried out at 1MW test operations done in 2018 and 2019. Plans of upgrading the spectrometer are currently being considered.

Journal Articles

Sequence-dependent hydration water dynamics of dodecameric DNA

Nakagawa, Hiroshi; Yonetani, Yoshiteru*; Nakajima, Kenji; Kawamura, Seiko; Kikuchi, Tatsuya*; Inamura, Yasuhiro; Kataoka, Mikio*; Kono, Hidetoshi*

JPS Conference Proceedings (Internet), 33, p.011101_1 - 011101_6, 2021/03

Hydration water dynamics were measured by quasi-elastic neutron scattering with Hn$$_{2}$$O/D$$_{2}$$O contrast for two DNA dodecamers, 5'CGCG$$underline{rm AATT}$$CGCG'3 and 5'CGCG$$underline{rm TTAA}$$CGCG'3, which have been computationally shown to be structurally rigid and flexible, respectively. The dynamical transitions of the hydration water as well as DNA were observed for both sequences at approximately 240 K. Above the transition temperature, the mean square displacements of the hydration water for the rigid sequence were smaller than those for the flexible one. Furthermore, the relaxation time of the hydration water was longer in the rigid DNA than in the flexible DNA. We suggest that hydration water dynamics on the picosecond timescale are associated with sequence-dependent deformability of DNA.

Journal Articles

Energy resolution and neutron flux of the 4SEASONS spectrometer revisited

Kajimoto, Ryoichi; Nakamura, Mitsutaka; Iida, Kazuki*; Kamazawa, Kazuya*; Ikeuchi, Kazuhiko*; Inamura, Yasuhiro; Ishikado, Motoyuki*

Journal of Neutron Research, 22(2-3), p.99 - 107, 2020/10

Journal Articles

Behavior of Sm in the boron cage of Sm-doped $$R$$B$$_{6}$$ ($$R$$ =Yb, La) observed by multiple-wavelength neutron holography

Uechi, Shoichi*; Oyama, Kenji*; Fukumoto, Yohei*; Kanazawa, Yuki*; Happo, Naohisa*; Harada, Masahide; Inamura, Yasuhiro; Oikawa, Kenichi; Matsuhra, Wataru*; Iga, Fumitoshi*; et al.

Physical Review B, 102(5), p.054104_1 - 054104_10, 2020/08

 Times Cited Count:1 Percentile:27.27(Materials Science, Multidisciplinary)

Journal Articles

$$q$$=0 long-range magnetic order in centennialite CaCu$$_{3}$$(OD)$$_{6}$$Cl$$_{2}$$ $$cdot$$ 0.6D$$_{2}$$O; A Spin-$$frac{1}{2}$$ perfect kagome antiferromagnet with $$J_{1}$$-$$J_{2}$$-$$J_{d}$$

Iida, Kazuki*; Yoshida, Hiroyuki*; Nakao, Akiko*; Jeschke, H. O.*; Iqbal, Y.*; Nakajima, Kenji; Kawamura, Seiko; Munakata, Koji*; Inamura, Yasuhiro; Murai, Naoki; et al.

Physical Review B, 101(22), p.220408_1 - 220408_6, 2020/06

 Times Cited Count:5 Percentile:78.11(Materials Science, Multidisciplinary)

Crystal and magnetic structures of the mineral centennialite CaCu$$_{3}$$(OD)$$_{6}$$Cl$$_{2}$$ $$cdot$$ 0.6D$$_{2}$$O are investigated by means of synchrotron X-ray diffraction and neutron diffraction measurements complemented by density functional theory (DFT) and pseudofermion functional renormalization group (PFFRG) calculations. In CaCu$$_{3}$$(OD)$$_{6}$$Cl$$_{2}$$ $$cdot$$ 0.6D$$_{2}$$O, Cu$$^{2+}$$ ions form a geometrically perfect kagome network with antiferromagnetic $$J_{1}$$. No intersite disorder between Cu$$^{2+}$$ and Ca$$^{2+}$$ ions is detected. CaCu$$_{3}$$(OD)$$_{6}$$Cl$$_{2}$$ $$cdot$$ 0.6D$$_{2}$$O enters a magnetic long-range ordered state below $$T_{rm N}$$ = 7.2 K, and the $$q$$=0 magnetic structure with negative vector spin chirality is obtained. The ordered moment at 0.3 K is suppressed to 0.58(2)$$mu$$B. Our DFT calculations indicate the presence of antiferromagnetic $$J_{2}$$ and ferromagnetic $$J_{d}$$ superexchange couplings of a strength which places the system at the crossroads of three magnetic orders (at the classical level) and a spin-$$frac{1}{2}$$ PFFRG analysis shows a dominance of $$q$$=0 type magnetic correlations, consistent with and indicating proximity to the observed $$q$$=0 spin structure. The results suggest that this material is located close to a quantum critical point and is a good realization of a $$J_{1}$$-$$J_{2}$$-$$J_{d}$$ kagome antiferromagnet.

Journal Articles

Horizontal line nodes in Sr$$_2$$RuO$$_4$$ proved by spin resonance

Iida, Kazuki*; Kofu, Maiko; Suzuki, Katsuhiro*; Murai, Naoki; Kawamura, Seiko; Kajimoto, Ryoichi; Inamura, Yasuhiro; Ishikado, Motoyuki*; Hasegawa, Shunsuke*; Masuda, Takatsugu*; et al.

Journal of the Physical Society of Japan, 89(5), p.053702_1 - 053702_5, 2020/05

 Times Cited Count:8 Percentile:83.36(Physics, Multidisciplinary)

Journal Articles

Emergent spin-1 Haldane gap and ferroelectricity in a frustrated spin-$$frac{1}{2}$$ ladder

Ueda, Hiroshi*; Onoda, Shigeki*; Yamaguchi, Yasuhiro*; Kimura, Tsuyoshi*; Yoshizawa, Daichi*; Morioka, Toshiaki*; Hagiwara, Masayuki*; Hagiwara, Masato*; Soda, Minoru*; Masuda, Takatsugu*; et al.

Physical Review B, 101(14), p.140408_1 - 140408_6, 2020/04

 Times Cited Count:2 Percentile:47.94(Materials Science, Multidisciplinary)

Journal Articles

Preparation, thermoelectric properties, and crystal structure of boron-doped Mg$$_{2}$$Si single crystals

Hayashi, Kei*; Saito, Wataru*; Sugimoto, Kazuya*; Oyama, Kenji*; Hayashi, Koichi*; Happo, Naohisa*; Harada, Masahide; Oikawa, Kenichi; Inamura, Yasuhiro; Miyazaki, Yuzuru*

AIP Advances (Internet), 10(3), p.035115_1 - 035115_7, 2020/03

 Times Cited Count:4 Percentile:71.61(Nanoscience & Nanotechnology)

Journal Articles

The $$f$$-electron state of the heavy fermion superconductor NpPd$$_5$$Al$$_2$$ and the isostructural family

Metoki, Naoto; Aczel, A. A.*; Aoki, Dai*; Chi, S.*; Fernandez-Baca, J. A.*; Griveau, J.-C.*; Hagiwara, Masato*; Hong, T.*; Haga, Yoshinori; Ikeuchi, Kazuhiko*; et al.

JPS Conference Proceedings (Internet), 30, p.011123_1 - 011123_6, 2020/03

Rare earths (4$$f$$) and actinides (5$$f$$) provide variety of interesting states realized with competing interactions between the increasing number of $$f$$ electrons. Since crystal field splitting of many-body $$f$$ electron system is smaller than the bandwidth, (1) high resolution experiments are needed, (2) essentially no clear spectrum with well defined peaks is expected in itinerant Ce and U compounds, and (3) Np and Pu is strictly regulated. Therefore, systematic research on magnetic excitations by neutron scattering experiments of localized compounds and rare earth iso-structural reference is useful. We describe the $$f$$ electron states of heavy electron compounds NpPd$$_5$$Al$$_2$$ and actinide and rare earth based iso-structural family.

Journal Articles

Q dependence of magnetic resonance mode on FeTe$$_{0.5}$$Se$$_{0.5}$$ studied by inelastic neutron scattering

Ishikado, Motoyuki*; Kodama, Katsuaki; Kajimoto, Ryoichi; Nakamura, Mitsutaka; Inamura, Yasuhiro; Ikeuchi, Kazuhiko*; Ji, S.*; Arai, Masatoshi*; Shamoto, Shinichi

Condensed Matter (Internet), 4(3), p.69_1 - 69_10, 2019/09

The enhancement magnetic resonance mode of FeTe$$_{0.5}$$Se$$_{0.5}$$ is limited around Q = ($$pi$$, 0). Q dependence is found to be consistent with a theoretical simulation of the magnetic resonance mode with the sign-reversing order parameter of s$$pm$$wave.

Journal Articles

Background issues encountered by cold-neutron chopper spectrometer AMATERAS

Kikuchi, Tatsuya*; Nakajima, Kenji; Kawamura, Seiko; Inamura, Yasuhiro; Nakamura, Mitsutaka; Wakai, Daisuke*; Aoyama, Kazuhiro*; Iwahashi, Takaaki*; Kambara, Wataru*

Physica B; Condensed Matter, 564, p.45 - 53, 2019/07

 Times Cited Count:0 Percentile:0(Physics, Condensed Matter)

Details of the background, that is, unwanted signals accumulated by the data acquisition system of neutron instruments, observed by the cold-neutron chopper spectrometer AMATERAS installed at the Materials and Life Science Experimental Facility at J-PARC are reported. In the design phase of AMATERAS, we carefully considered the achievement of high signal-to-noise ratio, and possible countermeasures were implemented. Actually, recent scientific outputs from AMATERAS indicates that the spectrometer is one of excellent neutron instruments with low background. In spite of that, in nine years of AMATERAS operation, we have encountered unwanted signals due to various reasons, including gamma-rays emitted at materials on or near the beam line including the sample itself, scattered neutrons from the beam line devices, air scattering, electronic noise in data acquisition system, cosmic rays, T0 burst, and other unknown sources. In this report, we discuss the background observed by AMATERAS, especially in the conditions of without samples, comprehensively. The possible sources of these signals and the countermeasures considered against the above sources are discussed, which may be helpful to those who are engaged in other existing or planned neutron-scattering instruments.

Journal Articles

Quantum dynamics of hydrogen in the iron-based superconductor LaFeAsO$$_{0.9}$$D$$_{0.1}$$ measured with inelastic neutron spectroscopy

Yamaura, Junichi*; Hiraka, Haruhiro*; Iimura, Soshi*; Muraba, Yoshinori*; Bang, J.*; Ikeuchi, Kazuhiko*; Nakamura, Mitsutaka; Inamura, Yasuhiro; Honda, Takashi*; Hiraishi, Masatoshi*; et al.

Physical Review B, 99(22), p.220505_1 - 220505_6, 2019/06

 Times Cited Count:1 Percentile:11.39(Materials Science, Multidisciplinary)

Inelastic neutron scattering was performed for an iron-based superconductor, where most of D (deuterium) replaces oxygen, while a tiny amount goes into interstitial sites. By first-principle calculation, we characterize the interstitial sites for D (and for H slightly mixed) with four equivalent potential minima. Below the superconducting transition temperature Tc = 26 K, new excitations emerge in the range 5-15 meV, while they are absent in the reference system LaFeAsO$$_{0.9}$$F$$_{0.1}$$. The strong excitations at 14.5 meV and 11.1 meV broaden rapidly around 15 K and 20 K, respectively, where each energy becomes comparable to twice of the superconducting gap. The strong excitations are ascribed to a quantum rattling, or a band motion of hydrogen, which arises only if the number of potential minima is larger than two.

Journal Articles

Study on use of superconducting magnet and first inelastic neutron scattering experiment under magnetic field at 4SEASONS spectrometer

Kajimoto, Ryoichi; Ishikado, Motoyuki*; Kira, Hiroshi*; Kaneko, Koji; Nakamura, Mitsutaka; Kamazawa, Kazuya*; Inamura, Yasuhiro; Ikeuchi, Kazuhiko*; Iida, Kazuki*; Murai, Naoki; et al.

Physica B; Condensed Matter, 556, p.26 - 30, 2019/03


 Times Cited Count:2 Percentile:23.12(Physics, Condensed Matter)

Journal Articles

Quantum magnetisms in uniform triangular lattices Li$$_{2}$$$$A$$Mo$$_{3}$$O$$_{8}$$ ($$A$$ = In, Sc)

Iida, Kazuki*; Yoshida, Hiroyuki*; Okabe, Hirotaka*; Katayama, Naoyuki*; Ishii, Yuto*; Koda, Akihiro*; Inamura, Yasuhiro; Murai, Naoki; Ishikado, Motoyuki*; Kadono, Ryosuke*; et al.

Scientific Reports (Internet), 9(1), p.1826_1 - 1826_9, 2019/02

 Times Cited Count:5 Percentile:63.62(Multidisciplinary Sciences)

Journal Articles

Anomaly of structural relaxation in complex liquid metal of bismuth; Dynamic correlation function of coherent quasi-elastic neutron scattering

Kawakita, Yukinobu; Kikuchi, Tatsuya*; Inamura, Yasuhiro; Tahara, Shuta*; Maruyama, Kenji*; Hanashima, Takayasu*; Nakamura, Mitsutaka; Kiyanagi, Ryoji; Yamauchi, Yasuhiro*; Chiba, Kaori*; et al.

Physica B; Condensed Matter, 551, p.291 - 296, 2018/12

 Times Cited Count:7 Percentile:49.86(Physics, Condensed Matter)

There are elemental liquid metals with complex structures far from the hard sphere (HS) packing model. Liquid Bi has an asymmetric first peak in the structure factors S(Q). The pair distribution function g(r) exhibits strange distance ratio of 1:2 between the first and the second peaks. Since a HS model with two kinds of radius produces asymmetry of the main peak in S(Q), existence of short-lived covalent bonds was discussed. Contrarily, modulation of the atomic distribution by the Friedel oscillations of shielding electrons around metallic ions was discussed. To examine its bonding nature from viewpoints of dynamic correlation functions, we have measured neutron quasielastic scattering of liquid Bi by using cold disk chopper spectrometer installed at MLF of J-PARC. The van Hove function revealed that the shoulder structure located at a longer side of the first peak in g(r) exhibits a longer relaxation time than the main structures such as the first and second peaks.

Journal Articles

Neutron inelastic scattering study of the $$f$$-electron states in NdPd$$_5$$Al$$_2$$

Metoki, Naoto; Yamauchi, Hiroki; Suzuki, Hiroyuki*; Kitazawa, Hideaki*; Kamazawa, Kazuya*; Ikeuchi, Kazuhiko*; Kajimoto, Ryoichi; Nakamura, Mitsutaka; Inamura, Yasuhiro

Journal of the Physical Society of Japan, 87(8), p.084708_1 - 084708_7, 2018/08

 Times Cited Count:5 Percentile:54.73(Physics, Multidisciplinary)

Inelastic neutron scattering experiments were carried out in order to study the $$f$$-electron states of NdPd$$_5$$Al$$_2$$The CEF levels at 0K, 35.4K, 88.3K, 101.5K, and 198.8K were clarified from the excitation spectra. The $$Gamma_6$$ ground state contains the orbital with $$J_z=pm9/2$$ as a main component due to a large negative B$$_{20}=-1.4$$K, which is the origin of the strong uniaxial anisotropy. The estimated magnetic moment, the calculated susceptibility, magnetization curve, and specific heat are in good agreement with the experimental data. The existence of a common charge distribution with CePd$$_5$$Al$$_2$$ and PrPd$$_5$$Al$$_2$$. Indicates that a localized character is important even in actinide-based iso-structural compounds as actually observed in UPd$$_5$$Al$$_2$$ and also NpPd$$_5$$Al$$_2$$, in which the valence crossover plays important role for the heavy fermion superconductivity.

Journal Articles

Phase-transition kinetics of magnetic skyrmions investigated by stroboscopic small-angle neutron scattering

Nakajima, Taro*; Inamura, Yasuhiro; Ito, Takayoshi*; Oishi, Kazuki*; Oike, Hiroshi*; Kagawa, Fumitaka*; Kikkawa, Akiko*; Taguchi, Yasujiro*; Kakurai, Kazuhisa*; Tokura, Yoshinori*; et al.

Physical Review B, 98(1), p.014424_1 - 014424_5, 2018/07

 Times Cited Count:4 Percentile:33.32(Materials Science, Multidisciplinary)

We investigated the phase-transition kinetics of magnetic skyrmion lattice (SkL) in MnSi by means of stroboscopic small-angle neutron scattering (SANS). Temporal evolutions of SANS patterns were measured with time resolution of 13 ms while sweeping temperature as fast as 50 Ks$$^{-1}$$. It turned out that the paramagnetic-to-SkL transition immediately occurs upon traversing the equilibrium phase boundary on the rapid cooling, whereas the SkL-to-conical transition can be kinetically avoided to realize the low-temperature metastable SkL with a long-range magnetic order. The formation of the metastable SkL was found to be strongly dependent not only on cooling rate, but also on magnetic eld and trajectory in the H-T phase diagram.

331 (Records 1-20 displayed on this page)