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mimFeCl古府 麻衣子; 綿貫 竜太*; 榊原 俊郎*; 河村 聖子; 中島 健次; 上木 岳士*; 阿久津 和宏*; 山室 修*
no journal, ,
イオン液体は現代の液体科学分野で注目されている多機能液体であり、その特性はイオン種の選択に 応じて変えることができる。たとえば、磁性イオンを含む陰イオン種を選択すると磁気特性が現れる。最初に報告された磁性イオン液体CmimFeClは、冷却速度を調整することによりガラス・結晶の両方の状態をつくることができる。興味深いことに、結晶では反強磁性磁気秩序が、ガラスではスピングラス状態が発現する。我々は、中性子散乱測定を行い、結晶ではスピン波励起、ガラスでは非分散かつブロードな磁気励起を観測した。このブロードな磁気励起は、スピングラス転移温度以下ではボーズ因子でスケールでき、構造ガラスにみられるボゾンピークと類似している。これは、周期性が欠如していることを反映し、マグノンが伝搬せずに局在化するためだと考えられる。この局在化した磁気励起は、スピンクラスターの形成を示唆している。
樹神 克明; 本田 孝志*; 池田 一貴*; 社本 真一; 大友 季哉*
no journal, ,
Magnetic pair distribution function (mPDF) gives a real-space information on a magnetic correlation of paired magnetic moments with a distance r. It is useful to determine magnetic structure in the systems only with short-range magnetic orderings, because it is obtained from Fourier transformation of the magnetic diffraction data including both the Bragg reflection and diffuse scattering. To develop the magnetic structural analysis using mPDF, we propose an alternative equation for the simulation of mPDF and the process of estimation of the experimental mPDF from neutron diffraction data. Then, we applied the mPDF analysis to the short-range magnetic correlation in spin-glass material.
髭本 亘; 岡澤 赳*; 網田 裕斗; 宮崎 一輝*; 伊藤 孝; 吉田 良行*
no journal, ,
In a chiral superconductor, time reversal symmetry of Cooper pair breaks and spontaneous magnetic field can be generated in a superconducting phase. One of the possible source of the spontaneous magnetic field is current at the domain edges. Such the edge current is related to total orbital angular momentum of Cooper pairs and have been studied in chiral superconductors. Although spontaneous magnetic field is a key feature for understanding of chiral superconductivity, details are not known up to now. In Sr
RuO
, time reversal symmetry broken superconductivity is proposed. We have investigated anisotropy of spontaneous magnetic field in SrRuO by using zero field muon spin relaxation (ZF-
SR) technique. In superconducting phase, spontaneous magnetic fields were observed for all the directions. We will present anisotropy of spontaneous field based on our results of ZF-SR in SrRuO.
渡辺 真朗; 野尻 浩之*; 木原 工*
no journal, ,
これまで17テスラまでの超伝導DC磁石が中性子散乱実験のために開発されている。MLFでは、試料環境(SE)チームがSE装置として7テスラまでの超伝導DC磁石を運用しているが、一部のユーザーから、より高い磁場環境が要求されている。しかし、20テスラ以上を発生させるには、超伝導技術の摘要は困難で、大スペースを必要とする大型システムの構築が要求されるが、コスト、スペースの観点で非現実的である。そこでMLFでは、強磁場環境SE機器として、小エネルギー・小型化が可能なパルス磁場方式を採用することを決定し、開発を進めてきた。本発表では、新規に開発したコンパクトで可動式の30テスラを発生可能なパルスマグネットシステムについて報告する。
K
Li
)NbO
-based system with tetragonal structure米田 安宏; 宅和 千隼*
no journal, ,
Ceramics based on (Na,K)NbO have attracted considerable attention as an important type of lead-free and bismuth-free piezoelectric material in recent years because of their excellent piezoelectric properties. Synchrotron X-ray powder diffraction data were collected in the transmission mode at the beamlines BL04B2 and BL14B1 of SPring-8. The crystal structure fluctuates between tetragonal and orthothombic structures depending on Ta substitution. We used the Rietveld and PDF analyses of high-resolution synchrotron X-ray scattering data to bridge the local and average structures.
O
ceramic powder from high-energy X-ray diffraction米田 安宏; Fu, D.*
no journal, ,
In this work the structure of Ca
Ba
NbO
(CBN) ceramic was determined from sintered polycrystalline samples, by using high-energy X-ray diffraction with powder data, allowing a good refinement of the positional and vibrational parameters of the heavy metal atoms. Synchrotron X-ray powder diffraction data were collected in the transmission mode at the beamlines BL04B2 and BL14B1 of SPring-8. We used the Rietveld and PDF analyses of high-resolution synchrotron X-ray scattering data to bridge the local and average structures.
simulated with positively charged muons伊藤 孝; 髭本 亘; 幸田 章宏*; 下村 浩一郎*
no journal, ,
SrTiO格子中の水素不純物は格子間隙においてプロトン的に振舞うと言われている。一方で、還元処理により酸素空孔を導入したSrTiO
においては、水素は格子間隙に入るよりも酸素空孔に捕獲されてヒドリドとして存在する方がより安定であると言われている。我々はこの酸素置換型水素の安定性を微視的な観点から検証するために、SrTiO (
)のミュオンスピン緩和(
SR)測定を行った。SRは、高エネルギー粒子の照射により試料中に水素に対応するミュオニウム(Mu)欠陥を生成し、その電子状態および運動状態を解析する手法である。我々は、格子間Mu
が拡散を経て酸素空孔へ捕獲される過程のその場観測に成功した。これは置換型水素がより安定であることを強く示唆する結果である。
川崎 卓郎; Harjo, S.; 相澤 一也
no journal, ,
In order to extend the application scope of neutron diffraction in engineering study, a stroboscopic time-of-flight (TOF) neutron diffraction technique has been developed. In this study, the technique was applied to measuring the behavior of crystal lattices and domain switching of piezoelectric materials under cyclic electric fields. The diffraction intensities from a PZT-based piezoelectric actuator were measured at the Engineering Materials Diffractometer TAKUMI in J-PARC. The intensities in the parallel direction and the vertical direction to the applied field were measured simultaneously. The responses of the lattice and the domain to the field were successfully evaluated from the obtained diffraction patterns.
Harjo, S.; 川崎 卓郎; 土田 紀之*; 諸岡 聡; 相澤 一也
no journal, ,
Transformation induced plasticity (TRIP) phenomenon is paid attention because it gives a high work-hardening rate and a large uniform elongation as a result of deformation induced martensitic transformation during plastic loading. The deformation induced martensitic transformations in most metastable iron alloys occur after macro-yielding during deformation at room temperature (RT). There are arguments to explain whether the martensitic transformation during plastic loading is controlled by strain (the strain-induced transformation) or stress (the stress-assisted transformation). In this paper, we tried to observe the trigger of deformation induced martensitic transformation during tensile deformation by in situ tensile loading neutron diffraction (ND) of metastable iron alloys. In situ ND measurements during deformation have been confirmed as powerful tools to understand the strengthening mechanism during deformation of multiphase alloys.
Zn
Y
consisting of LPSO phase and 
Mg phaseHarjo, S.; 相澤 一也; Gong, W.*; 川崎 卓郎
no journal, ,
MgZnY alloy is a magnesium alloy with a duplex microstructure consisting of a long period stacking ordered (LPSO) phase and an Mg phase. Kink deformation was observed in an as-cast MgZnY alloy subjected to hot compression, and the refinement of LPSO via kinking was found to be the reason for strengthening of the material from microscopy analyses. However, direct evidences showing the increase in strength via kinking have not been observed so far. In the present work, in situ neutron diffraction was used to investigate the anisotropic deformation behavior of LPSO and Mg phases during uniaxial compression or tension in an as-cast MgZnY alloy and an extruded MgZnY alloy. The evolutions of phase stresses in both the LPSO and Mg phases were evaluated and discussed with the occurrences of twinning and kinking during compression or tension.
川北 至信; 松浦 直人*; 富永 大輝*; 山田 武*; 小林 誠*; 中川 洋
no journal, ,
J-PARC MLFのBL02に設置された飛行時間分析型後方散乱分光器DNAは生体分子, ソフトマター, 電池材料や強相関電子系などの固体物質を対象に、ピコ秒からナノ秒にわたる原子・スピンダイナミクスを解明するための中性子準弾性・非弾性散乱装置である。ガドリニウム中性子吸収剤をアナライザーミラーにバックコートすることで高い信号雑音比を達成している。DNAには最大300Hzで回転するパルス整形チョッパーの他、87.5
のブラッグ角で2.08meVの散乱中性子を取り出すSi111アナライザーミラーが設置されており、0.08
1.9(1/A)の運動量移行の領域をカバーする。最近、7.64meVの散乱中性子を選別し3.79(1/A)の運動量移行まで拡張できるSi311ミラーの設置を進めている。本発表では、Si311のコミッショニングの状況を含むDNAのスペックの紹介に加え、材料科学におけるいくつかの利用例を報告する。
studied by neutron scattering and their relation with thermal conductivities梶本 亮一; 中村 充孝; 村井 直樹; 社本 真一; 本田 孝志*; 池田 一貴*; 大友 季哉*; 畑 博人*; 江藤 貴弘*; 野田 正亮*; et al.
no journal, ,
The electron-doped SrTiO exhibits good thermoelectric properties. Recent studies indicated that only a few percent co-doping of La and Mn in SrTiO substantially reduces the thermal conductivity. Then, we investigated the static as well as dynamical structural properties of La and Mn-doped SrTiO by time-of-flight elastic and inelastic neutron scattering. We found that the La-Mn co-doped samples show tetragonal structures similar to the low-temperature structure of SrTiO, while the La-doped and Mn-doped samples maintain cubic structures with the same symmetry as the high-temperature structure of SrTiO. However, it is unlikely that it is the origin of the low thermal conductivity, since the structural transition in SrTiO does not significantly change the thermal conductivity. On the other hand, we found that the inelastic scattering spectrum shows a momentum-independent increase in the low-energy spectral weight by the co-doping. Interestingly, the increase in the low-energy spectral weight exhibits a clear correlation with thermal conductivity. The substitution of Sr
ions by La
ions results in the electron doping, and further doping of the Mn ions are expected to create Jahn-Teller active Mn ions. We consider that dynamical and local structural fluctuations caused by the Jahn-Teller instability in Mn ions coupled with the incipient ferroelectric nature of SrTiO induce additional low-energy scatterings and correspond to the origin of low thermal conductivity in the La and Mn co-doped compounds.