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Evidence of a structural quantum critical point in (Ca$$_x$$Sr$$_{1-x}$$)$$_3$$Rh$$_4$$Sn$$_{13}$$ from a lattice dynamics study

Cheung, Y. W.*; Hu, Y. J.*; 今井 正樹*; 谷奥 泰明*; 金川 響*; 村川 譲一*; 森山 広大*; Zhang, W.*; Lai, K. T.*; 吉村 一良*; et al.

Physical Review B, 98(16), p.161103_1 - 161103_5, 2018/10

 パーセンタイル:100(Materials Science, Multidisciplinary)

Approaching a quantum critical point has been an effective route to stabilize superconductivity. While the role of magnetic QCPs has been extensively discussed, similar exploration of a structural QCP is scarce. Using inelastic X-ray scattering, we examine the phonon spectrum of the nonmagnetic quasi-skutterudite (Ca$$_x$$Sr$$_{1-x}$$)$$_3$$Rh$$_4$$Sn$$_{13}$$, which represents a precious system to explore the interplay between structural instabilities and superconductivity by tuning the Ca concentration x. We unambiguously detect the softening of phonon modes around the M point on cooling towards the structural transition. Intriguingly, at x = 0:85, the soft mode energy squared at the M point extrapolates to zero at -5.7 K, providing the first compelling microscopic evidence of a structural QCP in (Ca$$_x$$Sr$$_{1-x}$$)$$_3$$Rh$$_4$$Sn$$_{13}$$. The enhanced phonon density-of-states at low energy provides the essential ingredient for realizing strong-coupling superconductivity near the structural QCP.


Effect of $$B$$-site randomness on the antiferroelectric/relaxor nature of the ground state; Diffuse and inelastic X-ray scattering study of Pb(In$$_{1/2}$$Nb$$_{1/2}$$)O$$_3$$

大和田 謙二*; 塚田 慎也*; 福田 竜生; 筒井 智嗣*; Baron, A. Q. R.*; 水木 純一郎*; 大和 英弘*; 安田 直彦*; 寺内 暉*

Physical Review B, 98(5), p.054106_1 - 054106_10, 2018/08

 パーセンタイル:100(Materials Science, Multidisciplinary)

The effect of $$B$$-site randomness on the antiferroelectric/relaxor nature of the ground state was investigated by studying diffuse and inelastic X-ray scattering from ordered and disordered Pb(In$$_{1/2}$$Nb$$_{1/2}$$)O$$_3$$ (O- and D-PIN) single crystals. The diffuse scattering measurement of O-PIN (antiferroelectric at $$T<T_N$$) shows the existence of ferroelectrically interactive local polarization above $$T_N$$. Inelastic X-ray scattering shows that the transverse-acoustic (TA) and transverse-optic (TO) modes are dominant at $$Tsim$$800 K, while the central peak (CP) and TA modes are coupled and majorly contribute to the critical behavior of the diffuse scattering at $$T_N$$. Upon these results, the $$B$$-site randomness is discussed in terms of suppressing the antiferroelectric instability and enhancing the polarization fluctuation.


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

 パーセンタイル:100(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).


Second-order structural transition in (Ca$$_{0.5}$$Sr$$_{0.5}$$)$$_3$$Rh$$_4$$Sn$$_{13}$$

Cheung, Y. W.*; Hu, Y. J.*; Goh, S. K.*; 金子 耕士; 筒井 智嗣; Logg, P. W.*; Grosche, F. M.*; 金川 響*; 谷奥 泰明*; 今井 正樹*; et al.

Journal of Physics; Conference Series, 807(3), p.032002_1 - 032002_4, 2017/04


(Ca$$_{0.5}$$Sr$$_{0.5}$$)$$_3$$Rh$$_4$$Sn$$_{13}$$ is a member of the substitution series (Ca$$_{x}$$Sr$$_{1-x}$$)$$_3$$Rh$$_4$$Sn$$_{13}$$ which has recently been argued to feature a structural quantum critical point at $$x_c$$ = 0.9. In the stoichiometric compound Sr$$_{3}$$Rh$$_{4}$$Sn$$_{13}$$, the structural transition at $$T^*$$ $$approx$$ 138 K has been shown to be a second-order phase transition. Moving towards xc, we examine the character of the structural transition in (Ca$$_{0.5}$$Sr$$_{0.5}$$)$$_3$$Rh$$_4$$Sn$$_{13}$$ (i.e. $$x$$ = 0.5, $$T^*$$ $$approx$$ 55 K) using electrical resistivity, heat capacity and X-ray scattering. The absence of the thermal hysteresis in specific heat around $$T^*$$, and the continuous evolution of the superlattice reflection detected by X-ray diffraction are consistent with the scenario that the structural transition associated with a modulation vector $$q$$ = (0.5, 0.5, 0) in (Ca$$_{0.5}$$Sr$$_{0.5}$$)$$_3$$Rh$$_4$$Sn$$_{13}$$ remains second-order on approaching the quantum critical point.


Impurity effects in the microscopic elastic properties of polycrystalline Mg-Zn-Y alloys with a synchronised long-period stacking ordered phase

細川 伸也*; 木村 耕治*; 山崎 倫昭*; 河村 能人*; 吉田 亨次*; 乾 雅祝*; 筒井 智嗣*; Baron, A. Q. R.*; 川北 至信; 伊藤 晋一*

Journal of Alloys and Compounds, 695, p.426 - 432, 2017/02

 被引用回数:2 パーセンタイル:60.17(Chemistry, Physical)

Inelastic X-ray scattering (IXS) was performed on polycrystalline Mg$$_{97}$$Zn$$_1$$Y$$_2$$ and Mg$$_{85}$$Zn$$_6$$Y$$_9$$ alloys with synchronized long-period stacking ordered (LPSO) phase for investigating the impurity effects in the microscopic elastic properties. Inelastic neutron scattering (INS) was also carried out on the former alloy. LA modes were clearly observed in the IXS spectra of both the LPSO alloys, while TA modes can mainly be detected in the second Brillouin zone. Broader inelastic signals and larger quasielastic peaks are characteristic due to the phonon scattering by the Zn/Y impurities. Only the TA excitation energies increase by adding the impurities, which indicates a harder stiffness of the bond angles relating to the L1$$_2$$-type clusters in the LPSO alloys. New dispersion-less excitation modes are observed at about 10 meV by adding the Zn/Y impurities. By comparing with the INS data, the contributions of the impurities to these excitations are discussed using differences in the scattering cross-sections between neutrons and X-rays.


Numerical simulation on molten metal collision behavior using SPH method combined with fractal analysis on morphology of stacking pattern

二川 正敏; 筒井 喜平*; 粉川 広行; 直江 崇

Key Engineering Materials, 715, p.203 - 209, 2016/11

世界的関心の寄せられる様々な科学技術を展開しうる大強度陽子加速器施設では、加速器から出射されるMW級の大強度陽子線に耐えつつ、効率よく2次粒子を生成する標的が要求される。固体金属標的は、大強度の陽子線が入射することによって非常に高い熱流束が負荷され、場合によっては瞬時に溶融することが推測される。実際、J-PARC(Japan Proton Accelerator Research Complex)では、金の固体標的が局所的に溶融し、溶融金が噴出する事象が生じた。溶融金ジェットは真空を隔てるフランジ板に衝突して飛散すると共に、一部はフランジ板に付着した。この挙動を粒子法による数値解析で再現し、フランジ板上の付着痕の様相と衝突速度との相関について、フラクタル解析を導入して定量評価を試みた。その結果、フラクタル次元は衝突速度に依存し、局所衝撃力や飛散挙動を評価する指標として有効であることが分かった。


Effect of magnetism on lattice dynamics in SrFe$$_2$$As$$_2$$ using high-resolution inelastic X-ray scattering

村井 直樹*; 福田 竜生; 小林 達也*; 中島 正道*; 内山 裕士*; 石川 大介*; 筒井 智嗣*; 中村 博樹; 町田 昌彦; 宮坂 茂樹*; et al.

Physical Review B, 93(2), p.020301_1 - 020301_5, 2016/01

 被引用回数:4 パーセンタイル:57.78(Materials Science, Multidisciplinary)

Phonon spectra of detwinned SrFe$$_2$$As$$_2$$ crystals, as measured by inelastic X-ray scattering, show clear anisotropyaccompanying the magnetostructural transition at 200 K. We model the mode splitting using magnetic DFT calculations, including a phenomenological reduction in force-constant anisotropy that can be attributed to magnetic fluctuations. This serves as a starting point for a general model of phonons in this material applicable to both the antiferromagnetically ordered phase and the paramagnetic phase. Using this model, the measured splitting in the magnetic phase below T$$_N$$, and the measured phonon linewidth, we set a lower bound on the mean magnetic fluctuation frequency above T$$_N$$ at 210 K.


M$"o$ssbauer spectroscopy of actinide compounds

筒井 智嗣

M$"o$ssbauer Effect Reference and Data Journal, 38(4), p.105 - 111, 2015/06



X-ray absorption spectroscopy and novel electronic properties in heavy fermion compounds YbT$$_{2}$$Zn$$_{20}$$ (T: Rh and Ir)

本多 史憲*; 広瀬 雄介*; 三宅 厚志*; 水牧 仁一朗*; 河村 直己*; 筒井 智嗣*; 綿貫 徹; 渡辺 真仁*; 竹内 徹也*; 摂待 力生*; et al.

Journal of Physics; Conference Series, 592(1), p.012021_1 - 012021_5, 2015/03

 被引用回数:1 パーセンタイル:43.74

重い電子系化合物YbT$$_{2}$$Zn$$_{20}$$(T: Rh and Ir)について、X線吸収分光法によりYb価数観察を行った。いずれの化合物でもYb価数は温度依存性を示し、約100K以下で冷却とともにYb価数が減少する変化が見られた。これは、同型化合物であるYbCo$$_{2}$$Zn$$_{20}$$において温度依存性が見られないこととは対照的な結果である。


Zirconia membrane ECP electrode for water chemistry experiments in the JMTR

塙 悟史; 端 邦樹; 柴田 晃; 知見 康弘; 笠原 茂樹; 筒井 伸行*; 岩瀬 彰宏*; 西山 裕孝

Proceedings of 2014 Nuclear Plant Chemistry Conference (NPC 2014) (USB Flash Drive), 9 Pages, 2014/10



Anharmonic Pr guest modes in Pr(Os$$_{1-x}$$Ru$$_x$$)$$_4$$Sb$$_{12}$$ investigated by inelastic X-ray scattering

筒井 智嗣; 金子 耕士; 宮崎 亮一*; 東中 隆二*; 青木 勇二*; 小林 理気*; 脇本 秀一; Baron, A. Q. R.*; 菅原 仁*; 佐藤 英行*

JPS Conference Proceedings (Internet), 3, p.011060_1 - 011060_5, 2014/06

We have investigated the Ru/Os concentration dependence of the Pr guest mode in Pr(Os$$_{1-x}$$Ru$$_x$$)$$_4$$Sb$$_{12}$$ and its variation with temperature. The Pr guest mode at 3.2 meV in PrOs$$_4$$Sb$$_{12}$$ at the N point linearly shifts to a higher energy with the substitution of Ru into the Os site. The energy of the Pr guest mode decreases with decreasing temperature for all compositions, indicating the presence of an anharmonic potential at the Pr site. The slope of the temperature dependence of the guest mode energy is steeper for pure PrOs$$_4$$Sb$$_{12}$$ than for the other Pr(Os$$_{1-x}$$Ru$$_x$$)$$_4$$Sb$$_{12}$$ compounds we measured. The present results imply the importance of the transition metal in determining anharmonicity in Pr(Os$$_{1-x}$$Ru$$_x$$)$$_4$$Sb$$_{12}$$.


Multi-spin-state dynamics during insulator-metal crossover in LaCoO$$_3$$

土居 篤典*; 藤岡 淳*; 福田 竜生; 筒井 智嗣*; 奥山 大輔*; 田口 康二郎*; 有馬 孝尚*; Baron, A. Q. R.*; 十倉 好紀*

Physical Review B, 90(8), p.081109_1 - 081109_4, 2014/01

 被引用回数:12 パーセンタイル:35.48(Materials Science, Multidisciplinary)

The phonon dynamics of spin-state crossover for perovskite LaCoO$$_3$$ was investigated using infrared and inelastic X-ray spectroscopy. We observed that the Co-O bond stretching phonons couples to the thermally excited spin-state. The momentum dispersion of the optical mode is anomalously dispersionless (less than 3 meV), and this supports the spin-state disproportionation scenario. The steep enhancement of spin-state fluctuation compared to the charge gap suggests the density dependent spin state disproportionation; a simple low spin (LS)/high spin (HS)- or LS/intermediate spin (IS)-state disproportionation is realized at the initial stage with dilute HS- (or IS-) state density, while the complex spin-state disproportionation involving all of the LS-, IS- and HS-state is formed when the density of HS- (or IS-) state is enhanced.


Temperature and magnetic field dependent Yb valence in YbRh$$_2$$Si$$_2$$ observed by X-ray absorption spectroscopy

中井 裕人*; 海老原 孝雄*; 筒井 智嗣*; 水牧 仁一朗*; 河村 直己*; 道村 真司*; 稲見 俊哉; 中村 俊幸*; 近藤 晃弘*; 金道 浩一*; et al.

Journal of the Physical Society of Japan, 82(12), p.124712_1 - 124712_5, 2013/12

 被引用回数:7 パーセンタイル:42.61(Physics, Multidisciplinary)



Study of exotic uranium compounds using $$^{238}$$U M$"o$ssbauer spectroscopy

筒井 智嗣; 中田 正美

M$"o$ssbauer Spectroscopy; Applications in Chemistry, Biology, and Nanotechnology, p.123 - 140, 2013/10

先端基礎研究センターで行われたウラン金属間化合物に関する$$^{238}$$Uメスバウア分光の結果に関してレビューを行った。われわれの研究以前には、$$^{238}$$U核の第1励起状態の核磁気モーメントの大きさが未知で、内部磁場を用いた磁性に関する定量分析は行うことができなかった。そこで、われわれは$$^{235}$$U NMRと$$^{238}$$Uメスバウア分光によるUO$$_{2}$$の内部磁場から$$^{238}$$U核の第1励起状態の核磁気モーメントを決定した。その後、種々のウラン金属間化合物、特に重い電子的振舞や2次元フェルミ面物質など、強相関電子系に分類される物質群についての$$^{238}$$Uメスバウア分光を行い、その物性の微 視電子状態について議論を行った。


Effect of B-site randomness on the antiferroelectric/relaxor nature of the ground state; Inelastic X-ray scattering study of Pb(In$$_{1/2}$$Nb$$_{1/2}$$)O$$_{3}$$

大和田 謙二; 福田 竜生; 水木 純一郎; 廣田 和馬*; 寺内 暉*; 筒井 智嗣*; Baron, A. Q. R.*; 大和 英弘*; 安田 直彦*

Journal of the Korean Physical Society, 59(3), p.2509 - 2514, 2011/09

 被引用回数:2 パーセンタイル:75.59(Physics, Multidisciplinary)

Pb(In$$_{1/2}$$Nb$$_{1/2}$$)O$$_{3}$$(PIN)はペロヴスカイトBサイトの秩序度により反強誘電状態,強誘電状態,リラクサー状態を取りうる物質である。秩序PINは鉛複合ペロヴスカイトPb(B'B'')O$$_{3}$$においてBサイトランダムネスのない系であり、Bサイトランダムネスによる反強誘電状態/リラクサー状態の起源を探るには理想的な物質である。われわれはX線非弾性散乱実験を行った。準弾性散乱(QE)は臨界スローダウンを示し横波音響(TA)フォノンは反強誘電転移点($$T_{rm N}$$)までソフト化を示す一方、横波光学モードは低温までソフト化を続けた。これらの結果は、反強誘電相転移はQEの起源とTAフォノンによるものであるが、強誘電相関は確固としてその背後に存在していることを示している。これらの結果を元に、Bサイトランダムネスの効果について議論する。


Evaluations of the new LiF-scintillator and optional brightness enhancement films for neutron imaging

飯倉 寛; 筒井 紀彰*; 中村 龍也; 片桐 政樹*; 呉田 昌俊; 久保 純*; 松林 政仁

Nuclear Instruments and Methods in Physics Research A, 651(1), p.100 - 104, 2011/09

 被引用回数:6 パーセンタイル:44.68(Instruments & Instrumentation)




谷 啓二*; 西尾 敏; 飛田 健次; 筒井 広明*; 三又 秀行*; 飯尾 俊二*; 青木 尊之*

電気学会論文誌,A, 129(9), p.569 - 574, 2009/09



Element and orbital-specific observation of two-step magnetic transition in NpNiGa$$_5$$; X-ray magnetic circular dichroism study

岡根 哲夫; 大河内 拓雄*; 稲見 俊哉; 竹田 幸治; 藤森 伸一; 河村 直己*; 鈴木 基寛*; 筒井 智嗣*; 山上 浩志; 藤森 淳; et al.

Physical Review B, 80(10), p.104419_1 - 104419_7, 2009/09

 被引用回数:6 パーセンタイル:65.01(Materials Science, Multidisciplinary)

X-ray magnetic circular dichroism (XMCD) experiments were performed at the Np $$M_{4,5}$$ and the Ga $$K$$ absorption edges of NpNiGa$$_5$$ to investigate the temperature-dependent changes of magnetic properties of Np 5$$f$$ and Ga 4$$p$$ electron states. By the sum-rule analysis of the Np $$M_{4,5}$$ XMCD data, the orbital magnetic moment $$mu_{mathrm{L}}$$ and the spin magnetic moment $$mu_{mathrm{S}}$$ were estimated for the Np 5$$f^3$$ and 5$$f^4$$ electronic configurations, and their comparison with the previous magnetization and neutron scattering experiments suggests that the 5$$f^4$$ configuration is more likely than the 5$$f^3$$ configuration in NpNiGa$$_5$$. It was found that $$|mu_{mathrm{L}}/mu_{mathrm{S}}|$$ tends to increase from the high-temperature low-moment ordered state to the low-temperature high-moment ordered state.


Unconventional ferroelectric transition in the multiferroic compound TbMnO$$_{3}$$ revealed by the absence of an anomaly in $$c$$-polarized phonon dispersion

梶本 亮一; 佐賀山 基*; 佐々井 健蔵*; 福田 竜生; 筒井 智嗣*; 有馬 孝尚*; 廣田 和馬*; 三井 由佳利*; 吉澤 英樹*; Baron, A. Q. R.*; et al.

Physical Review Letters, 102(24), p.247602_1 - 247602_4, 2009/06

 被引用回数:11 パーセンタイル:37.29(Physics, Multidisciplinary)

TbMnO$$_{3}$$ exhibits a spontaneous electric polarization along $$mathbf{c}$$ concomitantly with a spiral spin ordering modulated along $$mathbf{b}$$ below $$T$$$$_{rm c}$$ = 28 K. We have performed inelastic X-ray scattering measurements on a single crystal of TbMnO$$_{3}$$ to clarify whether phonon anomalies related to the ferroelectricity exist. We measured transverse modes, especially the Mn-O-Mn bending mode polarized along $$mathbf{c}$$ and propagating along $$mathbf{b}$$, which we expect is most relevant to the ferroelectricity. However, no anomaly was found in the phonon dispersion below 50 meV across $$T$$$$_{rm c}$$. The present result suggests that the mechanism of ferroelectricity in TbMnO$$_3$$ is different from that of a conventional displacive-type ferroelectric. The weak coupling between electric polarization and lattice in TbMnO$$_{3}$$ strongly suggests that the ferroelectricity is mainly derived from the spiral spin ordering.


Antiferroelectric correlation in relaxor Pb(In$$_{1/2}$$Nb$$_{1/2}$$)O$$_{3}$$ and ferroelectric correlation in antiferroelectric Pb(In$$_{1/2}$$Nb$$_{1/2}$$)O$$_{3}$$

大和田 謙二; 廣田 和馬*; 寺内 暉*; 福田 竜生; 筒井 智嗣*; Baron, A. Q. R.*; 水木 純一郎; 大和 英弘*; 安田 直彦*

Transactions of the Materials Research Society of Japan, 34(1), p.19 - 22, 2009/03


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