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前田 瑞穂*; 松田 達磨*; 芳賀 芳範; 白崎 謙次*; 木村 憲彰*
Journal of the Physical Society of Japan, 94(2), p.024707_1 - 024707_6, 2025/01
被引用回数:0 パーセンタイル:0.00(Physics, Multidisciplinary)We investigate the pressure dependence of the magnetoresistivity and Hall resistivity for an itinerant-electron metamagnet UCoAl. The first-order metamagnetic transition point varies as a function of hydrostatic pressure and terminates at the critical pressure 2.0 GPa. The electronic system, however, does not show criticality at this pressure but extends to higher pressures, unlike the usual quantum critical behavior.
筒井 智嗣; 伊藤 孝; 中村 仁*; 吉田 実生*; 小林 義男*; 依田 芳卓*; 中村 惇平*; 幸田 章宏*; 東中 隆二*; 青木 大*; et al.
Interactions (Internet), 245(1), p.55_1 - 55_9, 2024/12
Sm SR-based M
ssbauer and muon spin relaxation (
SR) spectroscopies have been applied to Sm
Ru
Ge
. The temperature dependence of the
Sm SR-based M
ssbauer spectra in the paramagnetic state implies the presence of dynamical nuclear Zeeman and/or quadrupole interactions. The time differential
SR spectra also exhibit a marked temperature dependence in the paramagnetic state, indicating the presence of magnetic fluctuation in Sm
Ru
Ge
at least. These results in the present work infer that the dynamical hyperfine interactions observed using the mutually complementary spectroscopic methods are connected with the mechanism of the heavy fermion behavior in Sm
Ru
Ge
.
筒井 智嗣; 東中 隆二*; 水牧 仁一朗*; 小林 義男*; 中村 仁*; 伊藤 孝; 依田 芳卓*; 松田 達磨*; 青木 勇二*; 佐藤 英行*
Interactions (Internet), 245(1), p.9_1 - 9_10, 2024/12
Sm synchrotron-radiation-based M
ssbauer spectroscopy has been applied to Sm-based heavy fermion intermetallics, Sm
Al
(
= Ti, V and Cr) and SmOs
Sb
. The isomer shifts obtained demonstrate that the Sm valence states in these compounds are intermediate. Since the difference of the isomer shifts in 22.502 keV
Sm M
ssbauer effect between Sm
and Sm
state is comparable to the 2nd order Doppler shift, consideration of the 2nd order Doppler shift is required to precisely discuss Sm valence state through the shifts of the M
ssbauer spectra. In addition, the plots of the isomer shifts obtained by the M
ssbauer spectroscopy against the Sm valence states estimated from Sm L-edge X-ray absorption spectroscopy exhibit a linear correlation except for that in SmOs
Sb
. This implies that the origin of the intermediate valence state in SmOs
Sb
differs from that in Sm
Al
(
= Ti, V and Cr).
大貫 惇睦*; 軽部 皓介*; 青木 大*; 仲村 愛*; 本間 佳哉*; 松田 達磨*; 芳賀 芳範; 竹内 徹也*
Journal of the Physical Society of Japan, 92(11), p.114703_1 - 114703_12, 2023/11
被引用回数:1 パーセンタイル:26.38(Physics, Multidisciplinary)Single crystal samples of a series of semimetallic magnet Eu(AsP
)
have successfully grown. By measuring magnetization, Hall resistivity and de Haas-van Alphen oscillations, large anomalous Hall resistivity arising from peculiar magnetic phase diagram was identified.
玉造 博夢; 長谷川 巧*; 佐賀山 基*; 水牧 仁一朗*; 村上 洋一*; 梶谷 丈*; 東中 隆二*; 松田 達磨*; 青木 勇二*; 筒井 智嗣*
Physical Review B, 107(2), p.024303_1 - 024303_8, 2023/01
被引用回数:1 パーセンタイル:15.88(Materials Science, Multidisciplinary)The phonon dispersion of a BiS-based superconductor LaBiS
O
F
is investigated by first-principles calculations and inelastic X-ray scattering experiments. The origin of superlattice (SL) reflections arising from transverse-type lattice modulation, which were recently reported in [J. Kajitani
., J. Phys. Soc. Jpn.
, 103601 (2021)], is discussed in terms of lattice dynamics. Our first-principles calculations of phonon dispersion and the Fermi surfaces (FSs) demonstrate that the phonon mode corresponding to the transverse-type lattice modulation is unstable, and the propagation vector corresponding to the SL reflections is close to the FS nesting vector, which suggests that the phonon softening originates from the FS nesting. Against these calculated expectations, measured phonon dispersion in LaBiS
O
F
along the Z-A direction, where the SL point is located, shows no remarkable temperature dependence, and there are no steeply declining branches accompanied with a softening around the SL point. Based on these results, we discuss the two possibilities for the transverse lattice modulation in LaBiS
O
F
: the order-disorder type structural transition and the displacive structural transition with an overdamped mode, for both of which the local structure distortion or the short range correlation within the BiS
plane would be essential.
岩佐 和晃*; Suyama, Kazuya*; 河村 聖子; 中島 健次; Raymond, S.*; Steffens, P.*; Yamada, Akira*; 松田 達磨*; 青木 勇二*; 川崎 郁斗; et al.
Physical Review Materials (Internet), 7(1), p.014201_1 - 014201_11, 2023/01
被引用回数:3 パーセンタイル:37.12(Materials Science, Multidisciplinary)The spin dynamics, crystalline-electric-field (CEF) level scheme, specific heat, and X-ray photoemission spectra (XPS) of CeRh
Sn
were investigated, which exhibits anomalous semimetal transport in the chiral crystallographic phase. CEF excitations observed at approximately 7 and 39 meV are consistent with the two inequivalent Ce-ion cites in the chiral structure. Because of broader CEF excitations and a strong 4
peak at the Fermi level in the Ce 4
on-resonance spectrum, the hybridized Ce 4
electrons contribute to the semimetal carriers. In addition, the spin fluctuation associated with the Kramers doublet ground state is characterized by the peak located at 0.15 meV. The electronic state involving the spin fluctuation causes the
behavior of specific heat below 0.6 K, which is attributed to linear dispersion relations of electrons of the Weyl Kondo semimetal in the chiral-lattice symmetry.
大貫 惇睦*; 青木 大*; 仲村 愛*; 松田 達磨*; 中島 美帆*; 芳賀 芳範; 竹内 徹也*
Journal of the Physical Society of Japan, 91(6), p.065001_1 - 065001_2, 2022/06
被引用回数:0 パーセンタイル:0.00(Physics, Multidisciplinary)Single crystals of -Mn and
-Mn are successfully grown. Non-Fermi-liquid relations of the low-temperature resistivity and specific heat are found in the spin-liquid state of
-Mn. On the other hand,
-Mn exhibits antiferromagnetic transition.
大貫 惇睦*; 金子 良夫*; 青木 大*; 仲村 愛*; 松田 達磨*; 中島 美帆*; 芳賀 芳範; 竹内 徹也*
Journal of the Physical Society of Japan, 91(6), p.065002_1 - 065002_2, 2022/06
被引用回数:2 パーセンタイル:30.07(Physics, Multidisciplinary)Single crystals of MnIrSi were grown using Bridgman method. Mn
IrSi shows a remarkable increase of the electrical resistivity below antiferromagnetic transition temperature accompanied by a large jump of specific heat.
大貫 惇睦*; 仲村 愛*; 青木 大*; 松田 達磨*; 芳賀 芳範; 播磨 尚朝*; 竹内 徹也*; 金子 良夫*
Journal of the Physical Society of Japan, 91(6), p.064712_1 - 064712_10, 2022/06
被引用回数:2 パーセンタイル:30.07(Physics, Multidisciplinary)Fermi surface of noncentrocymmetric FeP, Ni
P and Pd
Si was studied by means of de Haas-van Alphen experiments. The splitting energy of Fermi surfaces due to antisymmetric spin-orbit coupling is estimated.
筒井 智嗣; 東中 隆二*; 中村 頼人*; 藤原 孝将*; 中村 仁*; 小林 義男*; 伊藤 孝; 依田 芳卓*; 加藤 和男*; 新田 清文*; et al.
Hyperfine Interactions, 242(1), p.32_1 - 32_10, 2021/12
被引用回数:1 パーセンタイル:75.97(Physics, Atomic, Molecular & Chemical)Sm synchrotron-radiation-based M
ssbauer spectroscopy was performed in Sm-based intermetallics having a cubic crystal structure, Sm
Ge
, SmB
, SmBe
, and Sm
Al
(
= transition metals). In spite of the difference of the local structure around the Sm sites, the observed M
ssbauer spectra consist of a single line at 300 K. On the other hand, Sm L
-edge X-ray absorption spectra consist of two components, suggesting Sm
and Sm
states. Difference of the number of the spectral components between the M
ssbauer spectroscopy and X-ray absorption spectroscopy is caused by the difference of the time window in the scattering process of these measurements. Correlation between the isomer shifts in the M
ssbauer spectroscopy and average Sm valence states estimated from the X-ray absorption spectroscopy exhibits a linear correlation.
神戸 振作; 徳永 陽; 酒井 宏典; 松田 達磨*; 芳賀 芳範; Walstedt, R. E.*; 播磨 尚朝*
JPS Conference Proceedings (Internet), 30, p.011035_1 - 011035_5, 2020/03
最近の調査により、URuSi
の隠れた秩序と超伝導の対称性についての理解はかなり進んでいる。答えは遠くないようである。以下の問題と展望について議論する。
中根 僚宏*; 米山 翔太*; 兒玉 健*; 菊地 耕一*; 中尾 朗子*; 大原 高志; 東中 隆二*; 松田 達磨*; 青木 勇二*; 藤田 渉*
Dalton Transactions (Internet), 48(1), p.333 - 338, 2019/01
被引用回数:3 パーセンタイル:15.56(Chemistry, Inorganic & Nuclear)The two-dimensional quadratic lattice magnet, bis(glycolato)cobalt(II) ([Co(HOCHCO
)
]), showed anti-ferromagnetic ordering at 15.0 K and an abrupt increase in magnetisation at H = 22 600 Oe and 2 K, thereby acting as a metamagnet. Neutron diffraction studies suggested that the magnetic moment vectors of the Co(II) ions had an amplitude of 3.59 mB and were not aligned in a fully antiparallel fashion to those of their neighbours, which caused canting between the magnetic moment vectors in the sheet. The canting angle was determined to be 7.1deg. Canting induced net magnetisation in the sheet, but this magnetisation was cancelled between sheets. The magnetisations in the sheets were oriented parallel to the magnetic field at the critical magnetic field.
立岩 尚之; Pospil, J.*; 芳賀 芳範; 酒井 宏典; 松田 達磨*; 山本 悦嗣
Progress in Nuclear Science and Technology (Internet), 5, p.104 - 107, 2018/11
ウラン系強磁性超伝導物質UGe, URhGe, UCoGeについて盛んに研究が行われてきた。最近、我々は69個のウラン化合物、7個のネプツニウム化合物、4個のプルトニウム化合物について、スピンゆらぎ理論の適用性を検討した。その結果、アクチノイド5
電子の遍歴性を示唆する結果が得られた。会議では全強磁性化合物の解析結果と、UGe
のスピンのゆらぎパラーメーターの圧力依存を議論する。
神戸 振作; 徳永 陽; 酒井 宏典; 服部 泰佑; 比嘉 野乃花; 松田 達磨*; 芳賀 芳範; Walstedt, R. E.*; 播磨 尚朝*
Physical Review B, 97(23), p.235142_1 - 235142_10, 2018/06
被引用回数:22 パーセンタイル:67.29(Materials Science, Multidisciplinary)We report Si and
Ru NMR measurements on high-quality, single-crystal URu
Si
samples with a residual resistivity ratio RRR
70. Our results show that the Si and Ru sites exhibit 4-fold electronic symmetry around the
-axis in the hidden-order state. A previously observed 2-fold contribution of Si NMR linewidth is concluded to be due to extrinsic magnetic centers. Since the U and Si sites are aligned along the
-axis, we conclude further that the electronic state shows 4-fold symmetry around the U site below the hidden-order transition. From this observed local symmetry, possible space groups for the hidden-order state are
or
, based on group theoretical considerations. Since the order vector is considered to be
, the hidden-order state is then found to be
with rank 5 odd-parity, i.e. electric dotriacontapolar order.
竹田 幸治; 斎藤 祐児; 岡根 哲夫; 山上 浩志; 松田 達磨*; 山本 悦嗣; 芳賀 芳範; 大貫 惇睦*
Physical Review B, 97(18), p.184414_1 - 184414_7, 2018/05
被引用回数:3 パーセンタイル:13.76(Materials Science, Multidisciplinary)We have performed soft X-ray magnetic circular dichroism (XMCD) experiments on the itinerant-electron metamagnet UCoAl at the U 4-5
(
) and Co 2
-3
(
) absorption edges in order to investigate the magnetic properties of the U 5
and Co 3
electrons separately. From the line shape of the XMCD spectrum, it is deduced that the orbital magnetic moment of the Co 3
electrons is unusually large. Through the systematic temperature (
)- and magnetic field (
)-dependent XMCD measurements, we have obtained two types of the magnetization curve as a function of
and
(M-H curve and M-T curve, respectively). The metamagnetic transition from a paramagnetic state to a field-induced ferromagnetic state was observed clearly under 15 K at
. The value of the
and its
-dependence agree well between the U and Co sites, and the bulk magnetization. Whereas, we have discovered the remarkable differences in the M-H and M-T curves between the U and Co sites. The present findings show clearly that the role of the Co 3
electrons should be considered more carefully in order to understand the origin of the magnetic ordering in UCoAl.
神戸 振作; 服部 泰佑; 徳永 陽; 酒井 宏典; 松田 達磨*; 芳賀 芳範; Walstedt, R. E.*
Journal of Physics; Conference Series, 969(1), p.012033_1 - 012033_6, 2018/03
被引用回数:1 パーセンタイル:49.77(Physics, Applied)NMR核であるSi同位体を52%濃縮した高品質のURu
Si
を作成した。
Si同位体の自然存在比は、4%程度なので、この濃縮により測定積算時間を100分の1程度に短縮できる。この単結晶試料を用いた隠れた秩序相のSi-NMR線幅の結果は、既に報告した。今回は、この線幅の磁場、温度、角度依存に関するより詳細な解析について報告する。RKKYモデルによる2回対称の磁化率の分布の可能性に関しても議論する。
服部 泰佑; 酒井 宏典; 徳永 陽; 神戸 振作; 松田 達磨*; 芳賀 芳範
Physical Review Letters, 120(2), p.027001_1 - 027001_5, 2018/01
被引用回数:12 パーセンタイル:61.69(Physics, Multidisciplinary)In order to identify the spin contribution to superconducting pairing compatible with the so-called "hidden order", Si nuclear magnetic resonance measurements have been performed using a high-quality single crystal of URu
Si
. A clear reduction of the
Si Knight shift in the superconducting state has been observed under magnetic field applied along the crystalline
axis, corresponding to the magnetic easy axis. These results provide direct evidence for the formation of spin-singlet Cooper pairs. Consequently, results indicating a very tiny change of in-plane Knight shift reported previously demonstrate extreme uniaxial anisotropy for the spin susceptibility in the hidden order state.
立岩 尚之; Pospil, J.*; 芳賀 芳範; 酒井 宏典; 松田 達磨*; 山本 悦嗣
Physical Review B, 96(3), p.035125_1 - 035125_15, 2017/07
被引用回数:29 パーセンタイル:73.63(Materials Science, Multidisciplinary)69個のウラン強磁性物質、7個のネプツニウム強磁性物質、4個のプルトニウム強磁性物質について、Takahashiらによって提案されたスピンのゆらぎ理論(Y. Takahashi, J. Phys. Soc. Jpn. , 3553 (1986))を用いた解析を行った。基本的な磁気的パラメーターと、スピンのゆらぎパラメータを決定し、アクチノイド
電子系に対するスピンのゆらぎ理論の適用を考察した。
電子系の遍歴強磁性物質は一般化されたRhodes-Wohlfarthの関係式(
)を満たす。ここで
は自発磁化、
は有効磁気モーメント、
は強磁性転移温度である。
はスピンのゆらぎスペクトルのエネルギー空間における分布幅である。同じ関係式が、アクチノイド
電子系でも基本的に成立することが明らかにされた。
神戸 振作; 酒井 宏典; 徳永 陽; 服部 泰佑; Lapertot, G.*; 松田 達磨*; Knebel, G.*; Flouquet, J.*; Walstedt, R. E.*
Physical Review B, 95(19), p.195121_1 - 195121_8, 2017/05
被引用回数:3 パーセンタイル:15.60(Materials Science, Multidisciplinary)YbRhSi
の単結晶について、
Si核スピンエコー振動と減衰を測定した。これらの量は、300Kから20Kまで温度依存がないが、温度依存が20K以下であることを示している。これらの振動と減衰は、最近傍Si核間のRuderman-Kittelおよび擬似双極子相互作用によるものである。したがって、フェルミ準位近傍の電子状態は、20K以下で変化していることが結論できる。低温におけるフェルミ面の可能な改変について議論する。
松本 裕司*; 芳賀 芳範; 立岩 尚之; 青木 晴善*; 木村 憲彰*; 山村 朝雄*; 山本 悦嗣; 松田 達磨*; Fisk, Z.*; 山上 浩志*
Journal of the Physical Society of Japan, 85(10), p.104709_1 - 104709_7, 2016/10
被引用回数:3 パーセンタイル:26.07(Physics, Multidisciplinary)dHvA oscillations were detected on an actinide compound ThRuSi
which is regarded as a reference to strongly correlated electron systems URu
Si
and CeRu
Si
. Observed Fermi surfaces well coincides with the band structure calculations, as well as experimentally obtained ones for a heavy fermion compound CeRu
Si
. On the other hand, Fermi surfaces of URu
Si
have significantly different characteristics, suggesting an itinerant ground state of 5f electrons.