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Cr doping-induced ferromagnetism in the spin-glass Cd$$_{1-x}$$Mn$$_x$$Te studied by X-ray magnetic circular dichroism

Verma, V.*; 坂本 祥哉*; 石川 弘一郎*; Singh, V. R.*; 石上 啓介*; 芝田 悟朗; 門野 利治*; 小出 常晴*; 黒田 真司*; 藤森 淳*

Physica B; Condensed Matter, 642, p.414129_1 - 414129_5, 2022/10

 被引用回数:2 パーセンタイル:56.36(Physics, Condensed Matter)

The prototypical diluted magnetic semiconductor Cd$$_{1-x}$$Mn$$_x$$Te is a spin glass ($$x < 0.6$$) or an antiferromagnet ($$x > 0.6$$) but becomes ferromagnetic upon doping with a small amount of Cr atoms. To investigate the origin of the ferromagnetism in Cd$$_{1-x-y}$$Mn$$_x$$Cr$$_y$$Te, we have studied its element specific magnetic properties by X-ray absorption spectroscopy (XAS) and X-ray magnetic circular dichroism (XMCD). Measured XAS and XMCD spectra indicate that both Cr and Mn atoms are divalent and that the magnetic moments of Cr and Mn are aligned parallel. By analyzing the element-specific magnetization curves, we conclude that Cr doping leads to the formation of ferromagnetic or superparamagnetic clusters consisting of several Cr ions surrounded by a much larger number of Mn ions.


Neutron diffraction study on the deuterium composition of nickel deuteride at high temperatures and high pressures

齋藤 寛之*; 町田 晃彦*; 服部 高典; 佐野 亜沙美; 舟越 賢一*; 佐藤 豊人*; 折茂 慎一*; 青木 勝敏*

Physica B; Condensed Matter, 587, p.412153_1 - 412153_6, 2020/06

 被引用回数:2 パーセンタイル:18.58(Physics, Condensed Matter)

重水素を含んだfcc Niを、3.36GPaで1073Kから300Kへ冷却した際の、構造中の重水素(D)の席占有率を中性子その場観察により調べた。多くの重水素はfccの金属格子の八面体サイトを占め、またわずかながら四面体サイトへの占有も見られた。八面体サイトの占有率は、1073Kから300Kへの冷却で0.4から0.85へ増大した。一方、四面体サイトの占有率は約0.02のままであった。この温度に依存しない四面体サイトの占有率は普通でなく、その理由はよくわからない。水素による膨張の体積と水素組成の直線関係から、重水素の侵入による体積膨張は、2.09(13) ${AA $^{3}$/D}$原子と求められた。この値は、過去NiやNi$$_{0.8}$$ Fe$$_{0.2}$$合金で報告されている2.14-2.2 ${AA $^{3}$/D}$原子とよく一致している。


Applicability and limitations of $$G(r,E)$$ analysis transformed from the inelastic neutron scattering data

中村 充孝; 菊地 龍弥*; 川北 至信

Physica B; Condensed Matter, 567, p.61 - 64, 2019/08


 被引用回数:0 パーセンタイル:0(Physics, Condensed Matter)

最近、非弾性中性子散乱実験(INS)データから変換した実空間動的構造因子$$G(r,E)$$を用いた多結晶NaIのフォノンダイナミクスに関する研究報告を行った。この研究は、通常のINS実験条件(Q$$_{max} sim$$ 5$AA$^{-1}$$)であっても、物理的に十分意味のある実空間ダイナミクス情報が得られることを示したものであり、これまでに蓄積されてきた大量のINSデータの再利用と新たな視点での研究推進を促すものである。今回の発表では、$$G(r,E)$$解析の適用可能性とその限界について詳しく議論する。


Real time and real space analysis for coherent QENS and its application to liquid bismuth

菊地 龍弥*; 川北 至信

Physica B; Condensed Matter, 567, p.51 - 54, 2019/08

 被引用回数:0 パーセンタイル:0(Physics, Condensed Matter)

Real time and real space analysis for quasielastic neutron scattering (QENS) by means of the regularization method to estimate a spectrum has been developed. In our formalism, a mediation function between a dynamic structure factor, $$S(Q,omega)$$, and a time-space correlation function, $$P(r,t)$$,is estimated to minimize the sum of the least square fitting term for $$S(Q,omega)$$ in a $$Q-omega$$ space and the regularization term for $$P(r,t)$$ in a $$r-t$$ space. On the application to liquid bismuth which shows complicate static local structure, it is shown that a distribution function for Gaussian superposition to represent $$S(Q,omega)$$ has good characters as a mediating function. The $$S(Q,omega)$$ calculated from the estimated mediation function showed a good agreement with the experimental $$S_{exp}(Q,omega)$$ even for small acoustic phonon excitation in a low $$Q$$ region and gave more or less reasonable estimation of dynamic structure beyond the measured $$Q-omega$$ range. In addition of the main property of $$P(r,t)$$ that the ability to focus onto the relaxation process at a specific atomic distance helped us to understand a complicated layered structure in liquid bismuth, possibility of easy separation of self-diffusion from coherent QENS is shown.


Background issues encountered by cold-neutron chopper spectrometer AMATERAS

菊地 龍弥*; 中島 健次; 河村 聖子; 稲村 泰弘; 中村 充孝; 若井 大介*; 青山 和弘*; 岩橋 孝明*; 神原 理*

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

 被引用回数:1 パーセンタイル:6.16(Physics, Condensed Matter)

AMATERASはJ-PARC物質・生命科学実験施設に設置された冷中性子チョッパー型分光器である。この9年に亘る運用の中で得られたバッググラウンド(意図せずにデータ収集系に集積されるシグナル)についての知見をまとめた。それらは、ビームライン上にある物質から発生するガンマ線、ビームライン上にある機器から発生するブラッグ反射, 空気散乱, 電気ノイズ, 宇宙線などである。それらについてまとめると共に今後の可能な対策について述べる。これらは、同種の分光器にとっても役立つ情報となると期待する。


Status of neutron spectrometers at J-PARC

梶本 亮一; 横尾 哲也*; 中村 充孝; 川北 至信; 松浦 直人*; 遠藤 仁*; 瀬戸 秀紀*; 伊藤 晋一*; 中島 健次; 河村 聖子

Physica B; Condensed Matter, 562, p.148 - 154, 2019/06


 被引用回数:10 パーセンタイル:52.6(Physics, Condensed Matter)

Seven time-of-flight quasielastic/inelastic neutron scattering instruments are installed on six beamlines in the Materials and Life Science Experimental Facility (MLF) at the Japan Proton Accelerator Research Complex (JPARC). Four of these instruments are chopper-type direct-geometry spectrometers, one is a near-backscattering indirect-geometry spectrometer, and the other two are spin-echo-type spectrometers. This paper reviews the characteristic features, recent scientific outcomes, and progress in development of MLF spectrometers.


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

梶本 亮一; 石角 元志*; 吉良 弘*; 金子 耕士; 中村 充孝; 蒲沢 和也*; 稲村 泰弘; 池内 和彦*; 飯田 一樹*; 村井 直樹; et al.

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


 被引用回数:2 パーセンタイル:13.64(Physics, Condensed Matter)

Magnets are important for studying magnetism and are commonly used as sample environment devices of neutron scattering instruments. However, the use of magnets was prevented at the time-of-flight direct-geometry neutron spectrometer 4SEASONS in Materials and Life Science Experimental Facility (MLF) at J-PARC, because the instrument is surrounded by iron components, and it is equipped with a piece of equipment operated with magnetic bearings. In the present work, we investigate the influence of stray magnetic fields from a superconducting magnet which is shared among neutron scattering instruments in MLF. Based on the investigation, we modified 4SEASONS such that it can be used with the magnet. Finally, we successfully performed the first inelastic neutron scattering experiments with applied magnetic fields using this sample environment.


Recent progress on practical materials study by Bragg edge imaging at J-PARC

及川 健一; Su, Y.; 鬼柳 亮嗣; 川崎 卓郎; 篠原 武尚; 甲斐 哲也; 廣井 孝介; Harjo, S.; Parker, J. D.*; 松本 吉弘*; et al.

Physica B; Condensed Matter, 551, p.436 - 442, 2018/12

 被引用回数:3 パーセンタイル:18.48(Physics, Condensed Matter)

We are promoting for practical product observation by the energy-resolved neutron imaging method using high-intensity pulsed neutrons at J-PARC, under the Photon and Quantum Basic Research Coordinated Development Program from the Ministry of Education, Culture, Sports, Science and Technology, Japan. Bragg edge imaging, one of the energy-resolved neutron imaging methods for visualizing material properties, was applied to feasibility study of the temperature distribution of copper rod, complementary study of the texture and strain distribution of bent steel plates using neutron diffraction and EBSD, and so on. Outline of results obtained by these imaging experiments will be presented.


High-energy magnetic excitations in lightly oxygen-doped lanthanum nickel oxides

中島 健次; 梶本 亮一

Physica B; Condensed Matter, 551, p.142 - 145, 2018/12

 被引用回数:0 パーセンタイル:0(Physics, Condensed Matter)

We will report on magnetic excitations in lightly oxygen doped lanthanum nickel oxide, La$$_{2}$$NiO$$_{4+delta}$$. By introducing slightly excessive oxygen atoms in the system, magnetic excitations in La$$_{2}$$NiO$$_{4}$$ 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, La$$_{2}$$NiO$$_{4.02}$$ and La$$_{2}$$NiO$$_{4.11}$$ 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.


Study of the magnetization distribution in a grain-oriented magnetic steel using pulsed polarized neutron imaging

廣井 孝介; 篠原 武尚; 林田 洋寿*; Parker, J. D.*; Su, Y.; 及川 健一; 甲斐 哲也; 鬼柳 善明*

Physica B; Condensed Matter, 551, p.146 - 151, 2018/12

 被引用回数:5 パーセンタイル:29.93(Physics, Condensed Matter)

Grain oriented magnetic steel is widely used as a key material for magnetic industrial products. Since magnetic properties of steels are closely related to its magnetic domain structure, observation of the domain structure is important for understanding its magnetic properties. In this study, we attempted to observe the domain structure of a grain oriented steel using polarized pulsed neutron imaging. In the experiment, we first magnetized the sample by applying a magnetic field along the easy-to-magnetize direction via a coil, and confirmed the sample was magnetized almost uniformly from the obtained polarization distribution images. By analyzing the oscillatory behavior in the wavelength dependence of polarization, magnetization of the steel was estimated to be 1.82 T. Then, we removed the field and performed the same measurement. As a result, a striped domain structure was observed, with neighboring domains aligned anti-parallel to each other. From these results, it was demonstrated that our magnetic imaging method could visualize the magnetization and the direction of the domains in the practical steel.


Performances of oscillating radial collimator for the Fermi chopper spectrometer 4SEASONS at J-PARC

中村 充孝; 神原 理*; 飯田 一樹*; 梶本 亮一; 蒲沢 和也*; 池内 和彦*; 石角 元志*; 青山 和弘*

Physica B; Condensed Matter, 551, p.480 - 483, 2018/12


 被引用回数:3 パーセンタイル:18.48(Physics, Condensed Matter)



Phonon dynamics of NaI investigated by G($$r,E$$) analysis

中村 充孝; 菊地 龍弥*; 蒲沢 和也*; 川北 至信

Physica B; Condensed Matter, 551, p.351 - 354, 2018/12


 被引用回数:2 パーセンタイル:12.18(Physics, Condensed Matter)



Testing of time-of-flight neutron diffraction imaging using a high-resolution scintillator detector with wavelength-shifting fibers

川崎 卓郎; 中村 龍也; Gong, W.*; 及川 健一

Physica B; Condensed Matter, 551, p.460 - 463, 2018/12

 被引用回数:1 パーセンタイル:6.12(Physics, Condensed Matter)

Neutron diffraction is widely used for the investigation of lattice strain, texture and phase transformation in bulk materials. Although the distributions of these characteristics can be obtained by scanning the sample, the spatial resolution of the measurement is limited. Recently, Bragg-edge imaging technique is developed and adopted for the evaluations of lattice strain, crystal orientation and phase distributions in polycrystalline engineering materials such as steel. On the other hand, neutron diffraction imaging has a potential to be another technique for such purpose. Diffraction imaging at a pulsed neutron source requires a counting type two-dimensional position sensitive detector with high spatial resolution. We developed prototype imaging detector with wavelength-shifting fiber (WLSF) readout, and tried to observe sub grains in the b-Sn single crystal and grain distribution in the coarse-grained steel plate at NOBORU (BL10) of J-PARC MLF.


Characteristics of the 2012 model lithium-6 time-analyzer neutron detector (LiTA12) system as a high efficiency detector for resonance absorption imaging

甲斐 哲也; 佐藤 節夫*; 廣井 孝介; Su, Y.; 瀬川 麻里子; Parker, J. D.*; 松本 吉弘*; 林田 洋寿*; 篠原 武尚; 及川 健一; et al.

Physica B; Condensed Matter, 551, p.496 - 500, 2018/12

 被引用回数:2 パーセンタイル:6.12(Physics, Condensed Matter)

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.


Effect of upstream beam collimation on neutron phase imaging with a Talbot-Lau interferometer at the RADEN beam line in J-PARC

關 義親; 篠原 武尚; 上野 若菜; Parker, J. D.*; 松本 吉弘*

Physica B; Condensed Matter, 551, p.512 - 516, 2018/12

 被引用回数:3 パーセンタイル:18.48(Physics, Condensed Matter)

3枚の格子からなる中性子タルボ・ロー干渉計は高機能なイメージング装置であり、通常の吸収コントラスト像に加えて、微分位相コントラスト像とビジビリティコントラスト像も同時に取得することができる。我々はJ-PARC MLF RADENビームラインにおいて波長分解型のタルボ・ロー干渉計の開発を進めている。干渉パターンの波長分解解析を行うことで、白色ビーム測定で生じていた色収差による系統誤差を排除するとともに、より定量的な情報を引き出すことが可能になる。この波長分解測定・解析法を前提として、RADENビームラインの波長スペクトルに最適化した干渉計の設計(中心波長・格子周期・格子間距離)を決定した。


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

川北 至信; 菊地 龍弥*; 稲村 泰弘; 田原 周太*; 丸山 健二*; 花島 隆泰*; 中村 充孝; 鬼柳 亮嗣; 山内 康弘*; 千葉 薫*; et al.

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

 被引用回数:9 パーセンタイル:47.49(Physics, Condensed Matter)



Effect of gauge volume on strain measurement in rock materials using time-of-flight neutron diffraction

阿部 淳*; 関根 孝太郎*; Harjo, S.; 川崎 卓郎; 相澤 一也

Physica B; Condensed Matter, 551, p.283 - 286, 2018/12

 被引用回数:1 パーセンタイル:6.12(Physics, Condensed Matter)

Our previous neutron diffraction measurements investigated strain accumulation mechanism(s) in rock materials under uniaxial compression. This technique, when applied to metallic materials, is suffered by surface effects, gauge volume size effects, and/or incident beam divergence that induce pseudo-strain. Knowledge of the pseudo-strain is therefore necessary for precise evaluation of strain value in a stressed rock material. This work investigated the effects of gauge volume and incident neutron beam divergence on pseudo-strain in rock materials via neutron diffraction experiments performed on three types of sandstone. Spurious peak shifts appeared depending on the gauge volume or incident neutron beam divergence. These peak shifts were inferred to be derived from the difference between a neutron-weighted center of gravity position and a geometric center of the gauge volume position. However, changing the gauge volume height did not cause shift in the peak position.


Dynamical quadrupole structure factor of frustrated ferromagnetic chain

大西 弘明

Physica B; Condensed Matter, 536, p.346 - 349, 2018/05

 被引用回数:1 パーセンタイル:6.12(Physics, Condensed Matter)

In a spin-1/2 $$J_{1}$$-$$J_{2}$$ Heisenberg chain with ferromagnetic $$J_{1}$$ and antiferromagnetic $$J_{2}$$, the ground state in high magnetic fields is a quadrupole state, the so-called spin nematic state. To understand the properties of the spin nematic state from the viewpoint of excitation dynamics, we have studied dynamical spin structure factors by density-matrix renormalization group methods. In the spin nematic regime, we find gapless longitudinal and gapped transverse spin excitation spectra, in accordance with quasi-long-ranged longitudinal and short-ranged transverse spin correlations, respectively. These features can be examined by inelastic neutron scattering experiments. However, they are indirect evidence for the spin nematic state. Here, we proceed to analyze dynamical quadrupole structure factors to clarify excitation dynamics in the quadrupole channel. We observe gapless excitations at $$q$$=$$pi$$, signaling quasi-long-ranged antiferro-quadrupole correlations. Information of spectral intensity distribution would be useful to discuss how we can detect the spin nematic state directly by experiments.


Magnetic excitations in the orbital disordered phase of MnV$$_2$$O$$_4$$

松浦 慧介*; 佐賀山 基*; 上原 周*; 新居 陽一*; 梶本 亮一; 蒲沢 和也*; 池内 和彦*; Ji, S.*; 阿部 伸行*; 有馬 孝尚*

Physica B; Condensed Matter, 536, p.372 - 376, 2018/05

 被引用回数:2 パーセンタイル:12.18(Physics, Condensed Matter)

We have investigated the temperature dependence of magnetic dynamics in a spinel-type vanadium oxide MnV$$_2$$O$$_4$$ by inelastic neutron scattering. The scattering intensity of excitation around 20 meV disappears in the collinear intermediate-temperature cubic-ferrimagnetic phase, which reveals that this excitation should be peculiar to the orbital ordered phase. We have found a weakly dispersive mode emergent from a non-integer wavevector $$(1.4,1.4,0)$$ at 56 K, which lies in the cubic-ferrimagnetic phase between non-coplanar ferrimagnetic and paramagnetic phases. This indicates that the probable presence of an incommensurate instability in the simple collinear structure.


Inelastic X-ray scattering of $$RT$$Al$$_3$$ ($$R$$ = La, Ce, $$T$$ = Cu, Au)

筒井 智嗣*; 金子 耕士; Pospisil, J.; 芳賀 芳範

Physica B; Condensed Matter, 536, p.24 - 27, 2018/05

 被引用回数:2 パーセンタイル:12.18(Physics, Condensed Matter)

Inelastic X-ray scattering (IXS) experiments of RTAl$$_3$$ ($$R$$ = La Ce, $$T$$ = Cu, Au) were carried out at 300 and 5.5 K. The spectra between LaCuAl$$_3$$ and CeCuAl$$_3$$ (LaAuAl$$_3$$ and CeAuAl$$_3$$) are nearly identical at both temperatures except for temperature factors such as temperature dependence of Bose factor in IXS spectra and effect on thermal expansion. This means that no evident temperature dependence of IXS spectra was observed in CeTAl$$_3$$ ($$T$$ = Cu, Au).

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