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Spin excitations of the $$S$$=1/2 one-dimensional Ising-like antiferromagnet BaCo$$_{2}$$V$$_{2}$$O$$_{8}$$ in transverse magnetic fields

奥谷 顕*; 大西 弘明; 木村 尚次郎*; 竹内 徹也*; 木田 孝則*; 森 道康; 三宅 厚志*; 徳永 将史*; 金道 浩一*; 萩原 政幸*

Journal of the Physical Society of Japan, 90(4), p.044704_1 - 044704_9, 2021/04

 被引用回数:0 パーセンタイル:0.01(Physics, Multidisciplinary)

The high-field multifrequency electron spin resonance (ESR), the magnetization, and the specific heat of single crystals of BaCo$$_{2}$$V$$_{2}$$O$$_{8}$$ (a quasi-one-dimensional Ising-like antiferromagnet with $$S=1/2$$) were measured in two different transverse magnetic fields: $$H parallel [100]$$ and $$H parallel [110]$$. A softening of the lowest ESR mode was observed near the saturation field of the magnetization around 40 T in $$H parallel [110]$$, whereas it occurs around 10 T in $$H parallel [100]$$, far below the saturation field. These observations were reproduced by numerical calculations using the density-matrix renormalization group methods, including the staggered magnetic fields induced by a uniform external magnetic field and the interchain magnetic exchange interaction. We found that the directional dependence of the lowest mode originates mainly from the remarkable angular dependence of the induced magnetic field. The interchain interaction is also quantitatively important for reproducing the experimental results. The directional dependence of the lowest mode is demonstrated by the particle-hole excitation of spinons using the Jordan-Wigner transformation.


Multi-step magnetic transitions in EuNiIn$$_4$$

池田 修悟*; 金子 耕士; 田中 佑季*; 川崎 卓郎; 花島 隆泰*; 宗像 孝司*; 中尾 朗子*; 鬼柳 亮嗣; 大原 高志; 望月 健生*; et al.

Journal of the Physical Society of Japan, 89(1), p.014707_1 - 014707_7, 2020/01

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

Magnetism in EuNiIn$$_4$$ has been studied by specific heat, magnetic susceptibility, magnetization, $$^{151}$$Eu M$"o$ssbauer spectroscopy, and neutron diffraction experiments. The specific heat shows two magnetic transitions at $$T_{rm N1}$$ and $$T_{rm N2}$$ at zero magnetic field. An antiferromagnetic ground state of EuNiIn$$_4$$ has a uniaxial magnetic anisotropy along the b-axis, revealed by the magnetic susceptibility and the M$"o$ssbauer spectroscopy. Single crystal neutron diffraction experiments clarify that this antiferromagnetic structure in the ground state is characterized by the commensurate propagation vector $$q$$ = (1/2, 1/2, 1/2) which reveals no distinct anomaly at $$T_{rm N2}$$. The magnetization curve along the b-axis at 2 K shows four successive magnetic field-induced transitions up to 50 kOe and, reaches 7 $${mu}_{rm B}$$/f.u. above 190 kOe, The magnetic phase diagram in EuNiIn$$_4$$ has unique characteristics with five magnetic states in low magnetic field.


Revising the 4${it f}$ symmetry in CeCu$$_{2}$$Ge$$_{2}$$; Soft X-ray absorption and hard X-ray photoemission spectroscopy

荒谷 秀和*; 中谷 泰博*; 藤原 秀紀*; 川田 萌樹*; 金井 惟奈*; 山神 光平*; 藤岡 修平*; 濱本 諭*; 久我 健太郎*; 木須 孝幸*; et al.

Physical Review B, 98(12), p.121113_1 - 121113_6, 2018/09


 被引用回数:3 パーセンタイル:25.37(Materials Science, Multidisciplinary)

We present a detailed study on the $$4f$$ ground state symmetry of the pressure-induced superconductor CeCu$$_2$$Ge$$_2$$ probed by soft X-ray absorption and hard X-ray photoemission spectroscopy. The revised Ce $$4f$$ ground states are determined as $$|{Gamma_7}rangle=sqrt{0.45}|{J_{z}=pm frac{5}{2}}rangle - sqrt{0.55}|{mp frac{3}{2}}rangle$$ with $$Sigmamathchar`-{rm type}$$ in-plane rotational symmetry. This gives an in-plane magnetic moment consistent with the antiferromagnetic moment as reported in neutron measurements. Since the in-plane symmetry is the same as that for the superconductor CeCu$$_2$$Si$$_2$$, we propose that the charge distribution along the $$c$$-axis plays an essential role in driving the system into a superconducting phase.


Magnetic field induced phenomena in UIrGe in fields applied along the $$b$$ axis

Posp$'i$$v{s}$il, J.*; 芳賀 芳範; 小濱 芳允*; 三宅 厚志*; 神戸 振作; 立岩 尚之; Vali$v{s}$ka, M.*; Proschek, P.*; Prokle$v{s}$ka, J.*; Sechovsk$'y$, V.*; et al.

Physical Review B, 98(1), p.014430_1 - 014430_7, 2018/07

 被引用回数:10 パーセンタイル:64.19(Materials Science, Multidisciplinary)

The metamagnetic transition between the antiferromagnetic and paramagnetic state in UIrGe has been studied at various temperatures by magnetization, heat capacity, and magnetocaloric effect measurements on a single crystal in static and pulsed magnetic fields applied along the orthorhombic $$b$$ axis. The first-order transition is accompanied by a dramatic increase of the Sommerfeld coefficient. A tentative scenario explaining these anomalies by antiferromagnetic correlations or short-range order in the paramagnetic state is discussed.


Experimental observation of temperature and magnetic-field evolution of the 4${it f}$ states in CeFe$$_{2}$$ revealed by soft X-ray magnetic circular dichroism

斎藤 祐児; 保井 晃*; 渕本 寛人*; 中谷 泰博*; 藤原 秀紀*; 今田 真*; 鳴海 康雄*; 金道 浩一*; 高橋 稔*; 海老原 孝雄*; et al.

Physical Review B, 96(3), p.035151_1 - 035151_5, 2017/07


 被引用回数:1 パーセンタイル:8.28(Materials Science, Multidisciplinary)

単結晶CeFe$$_2$$を用い、X線吸収(XAS)磁気円2色性(XMCD)の高精度実験により、その強磁性的秩序相におけるCe4$$f$$状態を調べた。Ce $$M_{4,5}$$ XMCDスペクトルは、温度及び磁場に依存した形状変化を示す一方、Ce $$M_{4,5}$$ XAS、Fe $$L_{2,3}$$ XAS及びXMCDスペクトルでは変化が観測されないという通常の強磁性体とは異なる現象が観測された。このような振る舞いは、Ce 4$$f^1$$配置の$$J=5/2$$基底状態と$$J=7/2$$状態が混ざり合ったことに由来すると解釈できる。外部摂動に対し非常に敏感なCe 4$$f$$状態は、本物質での強磁性相と反強磁相が隣接する磁気不安定性と関連付けることができる。我々の実験データは、混成の強い強磁性Ce化合物の物性に対して、貴重な情報を与える。


X-ray absorption spectroscopy in the heavy Fermion compound $$alpha$$-YbAlB$$_4$$ at high magnetic fields

寺島 拓*; 松田 康弘*; 久我 健太郎*; 鈴木 慎太郎*; 松本 洋介*; 中辻 知*; 近藤 晃弘*; 金道 浩一*; 河村 直己*; 水牧 仁一朗*; et al.

Journal of the Physical Society of Japan, 84(11), p.114715_1 - 114715_4, 2015/11

 被引用回数:2 パーセンタイル:24.27(Physics, Multidisciplinary)

$$alpha$$-YbAlB$$_4$$ shows strong valence fluctuation as well as heavy fermion behavior at low temperatures. It has been theoretically suggested that the quantum criticality owing to the valence fluctuation found in Yb ions plays an important role in the peculiar properties of this material. In this work, we measured the X-ray absorption spectra (XAS) and X-ray magnetic circular dichroism (XMCD) at the L3 edge of Yb ions in high magnetic fields of up to 40 T. It is found that the XAS are almost independent of the magnetic field at 2 K, which proves that there is no significant valence change in this field range. The XMCD spectrum exhibits a distinct negative peak at the low-energy side of the L3 edge as well as the main positive peak near the white line. The negative XMCD peak is attributed to the quadrupole transition between the 2p and 4f states, and gives us microscopic information on the 4f state. This finding supports the recent theoretical proposal that $$|J_Z=pm5/2rangle$$ is the ground state of the localized Yb magnetic moment, where $$J_Z$$ is the z-component of the total angular momentum of Yb$$^{3+}$$.


Synchrotron X-ray spectroscopy study on the valence state and magnetization in $$alpha$$-YbAl$$_{1-x}$$Fe$$_x$$B$$_4$$ ($$x=0.115$$) at low temperatures and high magnetic fields

寺島 拓*; 松田 康弘*; 久我 健太郎*; 鈴木 慎太郎*; 松本 洋介*; 中辻 知*; 近藤 晃弘*; 金道 浩一*; 河村 直己*; 水牧 仁一朗*; et al.

Journal of Physics; Conference Series, 592(1), p.012020_1 - 012020_6, 2015/03

 被引用回数:1 パーセンタイル:46.97

価数転移に伴う量子臨界現象が理論的に提案され、希土類金属間化合物における価数揺動現象が注目を集めている。最近、$$beta$$-YbAlB$$_4$$がチューニングなしで量子臨界を示すことと強い混合原子価状態にあることが見出された。この研究では我々は$$alpha$$-YbAl$$_{1-x}$$Fe$$_x$$B$$_4$$ ($$x=0.115$$)について磁化曲線とX線吸収を測定した。この物質は、局所的には$$beta$$-YbAlB$$_4$$と同一構造をもつ多形である。磁化測定とX線測定はそれぞれ55Tと40Tまで行った。Yb価数のわずかな上昇が磁化曲線が傾きの変化を示す磁場で観測された。


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:51.25(Physics, Multidisciplinary)



High-magnetic-field X-ray absorption and magnetic circular dichroism spectroscopy in the mixed-valent compound YbAgCu$$_4$$

中村 俊幸*; 松田 康弘*; Her, J.-L.*; 金道 浩一*; 道村 真司*; 稲見 俊哉; 水牧 仁一朗*; 河村 直己*; 鈴木 基寛*; Chen, B.*; et al.

Journal of the Physical Society of Japan, 81(11), p.114702_1 - 114702_11, 2012/11

 被引用回数:11 パーセンタイル:60.87(Physics, Multidisciplinary)



Suppression of $$f$$-electron itinerancy in CeRu$$_2$$Si$$_2$$ by a strong magnetic field

松田 康弘*; 中村 俊幸*; Her, J. L.*; 道村 真司*; 稲見 俊哉; 金道 浩一*; 海老原 孝雄*

Physical Review B, 86(4), p.041109_1 - 041109_4, 2012/07

 被引用回数:9 パーセンタイル:42.14(Materials Science, Multidisciplinary)



Valence fluctuation in YbAgCu$$_4$$ at high Magnetic fields

松田 康弘*; 中村 俊幸*; Her, J.-L.*; 金道 浩一*; 道村 真司*; 稲見 俊哉; 水牧 仁一朗*; 河村 直己*; 鈴木 基寛*; Chen, B.*; et al.

Journal of the Physical Society of Japan, 81(1), p.015002_1 - 015002_2, 2012/01

 被引用回数:10 パーセンタイル:58.53(Physics, Multidisciplinary)

YbAgCu$$_4$$の磁場誘起価数変化を35Tまでのパルス高磁場下で放射光X線吸収分光法から観測した。4.8KでのYbAgCu$$_4$$のYbの価数はメタ磁性転移で大きく増加することがわかった。55Tでの飽和価数は2.97と予想される。この値は、35Tでの$$Delta M/Delta v$$から評価した。また、この値は同様な化合物であるYbInCu$$_4$$の高温や高磁場でのYbの値とも一致する。この実験からは、理論から予測された通り、YbAgCu$$_4$$のメタ磁性転移は価数転移に由来するものであると結論する。


Orbital magnetism in Cd$$_2$$Os$$_2$$O$$_7$$ studied by X-ray magnetic circular dichroism

松田 康弘*; Her, J.-L.*; 道村 真司*; 稲見 俊哉; 鈴木 基寛*; 河村 直己*; 水牧 仁一朗*; 金道 浩一*; 山浦 淳一*; 広井 善二*

Physical Review B, 84(17), p.174431_1 - 174431_5, 2011/11

 被引用回数:20 パーセンタイル:66.81(Materials Science, Multidisciplinary)

Osの$$L_{2,3}$$吸収端でのX線磁気円二色性(XMCD)を227Kで金属絶縁体転移を示すCd$$_2$$Os$$_2$$O$$_7$$の反強磁性相で調べた。総和則に従えば、10Tと37TでのXMCDは、軌道磁気モーメントとスピン磁気モーメントの比として$$m_{rm L}/m_{rm S}=0.16pm0.02$$を与え、また、$$m_{rm L}$$$$m_{rm S}$$は平行であることを示した($$m_{rm L}parallel m_{rm S}$$)。これらの現象は異常であり、まず、予測されるOs$$^{5+}$$(5$$d^3$$)の立方結晶場中の基底状態は軌道一重項であり、次にHundの第三ルールからは$$m_{rm L}$$$$m_{rm S}$$は反平行であるべきである。スピン軌道相互作用が観測された軌道磁性を説明するためには重要であると考えるのが最もらしい。


Magnetic-field-induced metallic state in $$beta$$-US$$_2$$

杉山 清寛*; 広瀬 雄介*; 榎 健太郎*; 池田 修悟*; 山本 悦嗣; 立岩 尚之; 芳賀 芳範; 木田 孝則*; 萩原 政幸*; 金道 浩一*; et al.

Journal of the Physical Society of Japan, 80(Suppl.A), p.SA104_1 - SA104_3, 2011/07

 被引用回数:1 パーセンタイル:12.1(Physics, Multidisciplinary)

Magnetic and transport properties under high magnetic field were studied on a magnetic semiconductor $$beta$$-US$$_2$$. Large magnetization reaching 1.75 $$mu_{rm B}$$ has been observed at 50 T. At the same time, resistivity decreases drastically from insulating behavior at 0 T to almost metallic characteristics at 50 T. The results are discussed based on the magnetic polaron mechanism.


Magnetic and superconducting properties of CeRhGe$$_2$$ and CePtSi$$_2$$

広瀬 雄介*; 西村 尚人*; 本多 史憲*; 杉山 清寛*; 萩原 政幸*; 金道 浩一*; 竹内 徹也*; 山本 悦嗣; 芳賀 芳範; 松浦 直人*; et al.

Journal of the Physical Society of Japan, 80(2), p.024711_1 - 024711_12, 2011/02

 被引用回数:6 パーセンタイル:41.66(Physics, Multidisciplinary)

Magnetic and superconducting properties of CeRhGe$$_2$$ and CePtSI$$_2$$ have been investigated by bulk property measurements and neutron scattering experiments. CeRhGe$$_2$$ was found to order antiferromagnetically with an ordered moment 1.3 $$mu_{rm B}$$/Ce along the $$c$$-axis of the orthorhombic unit cell. High pressure resistivity measurements revealed a suppression of the antiferromagnetic transition with increasing pressure and the occurrence of superconductivity near the critical pressure where antiferromagnetism vanishes. Quantum-critical characteristics are expected to these compounds.


Magnetic field and pressure phase diagrams of uranium heavy-fermion compound U$$_2$$Zn$$_{17}$$

立岩 尚之; 池田 修悟*; 芳賀 芳範; 松田 達磨; 山本 悦嗣; 杉山 清寛*; 萩原 政幸*; 金道 浩一*; 大貫 惇睦*

Journal of the Physical Society of Japan, 80(1), p.014706_1 - 014706_8, 2011/01

 被引用回数:8 パーセンタイル:53.47(Physics, Multidisciplinary)

重い電子系化合物U$$_2$$Zn$$_{17}$$について53Tまでの磁化測定を行った。ネール温度$$T_{rm N}$$=9.7K以下の反強磁性状態で、32Tの強磁場中でメタ磁性転移が観測され、磁気相図が作成された。われわれは、U$$_2$$Zn$$_{17}$$の反強磁性転移の圧力効果をダイヤモンドアンビルセルを用いて行った。反強磁性転移温度は、4.7GPaまで圧力に強く依存せず、5GPa以上で加圧とともに増大する。電気抵抗の温度依存について理論解析の結果得られた、$$T^2$$項の係数$$A$$,反強磁性ギャップ$$Delta$$の圧力依存について議論する。


Metamagnetic behavior in heavy-fermion compound YbIr$$_2$$Zn$$_{20}$$

竹内 徹也*; 安井 慎一*; 戸田 雅敏*; 松下 昌輝*; 吉内 伸吾*; 大家 政洋*; 片山 敬亮*; 広瀬 雄介*; 吉谷 尚久*; 本多 史憲*; et al.

Journal of the Physical Society of Japan, 79(6), p.064609_1 - 064609_15, 2010/06

 被引用回数:39 パーセンタイル:84.51(Physics, Multidisciplinary)

Metamagnetic behavior of the heavy-fermion compound YbIr$$_2$$Zn$$_{20}$$ was studied by magnetization, de Haas-van Alphen effect, magnetoresistance, specific heat, thermal expansion and magnetostriction. Metamagnetic behavior was observed for all the physical properties at low temperatures. It is remarkable that the Fermi surfaces observed in the dHvA effect unchanges across the metamagnetic transition.


Magnetic and Fermi surface properties of CePd$$_5$$Al$$_2$$ and PrPd$$_5$$Al$$_2$$

中野 泰典*; 本多 史憲*; 竹内 徹也*; 杉山 清寛*; 萩原 政幸*; 金道 浩一*; 山本 悦嗣; 芳賀 芳範; 摂待 力生*; 山上 浩志*; et al.

Journal of the Physical Society of Japan, 79(2), p.024702_1 - 024702_9, 2010/02

 被引用回数:14 パーセンタイル:65.76(Physics, Multidisciplinary)

Single crystals of new rare-earth compounds CePd$$_5$$Al$$_2$$ and PrPd$$_5$$Al$$_2$$ were successfully grown. Magnetic property measurements have shown the existence of the crystal-electric-field effect in these compounds with a magnetic ground state for CePd$$_5$$Al$$_2$$ and a singlet ground state for PrPd$$_5$$Al$$_2$$. Fermi surfaces were determined for both compounds by the de Haas-van Alphen experiments, revealing a localized nature of $$f$$-electrons.


Heavy fermion state in YbIr$$_2$$Zn$$_{20}$$

吉内 伸吾*; 戸田 雅敏*; 松下 昌輝*; 安井 慎一*; 広瀬 雄介*; 大家 政洋*; 片山 敬亮*; 本多 史憲*; 杉山 清寛*; 萩原 政幸*; et al.

Journal of the Physical Society of Japan, 78(12), p.123711_1 - 123711_4, 2009/12

 被引用回数:37 パーセンタイル:83.65(Physics, Multidisciplinary)

High-field magnetization and de Haas-van Alphen effect were measured on a heavy fermion compound YbIr$$_2$$Zn$$_{20}$$. Large cyclotron masses ranging from 4 to 27 $$m_0$$ were detected in the dHvA experiment, and are found to be reduced at magnetic fields higher than 120 kOe. From the present experimental results together with the 4f-itinerant band calculations, the 4f electrons are considered to form heavy fermion state.


Possible existence of magnetic polaron in nearly ferromagnetic semiconductor $$beta$$-US$$_2$$

池田 修悟*; 酒井 宏典; 立岩 尚之; 松田 達磨; 青木 大*; 本間 佳哉*; 山本 悦嗣; 中村 彰夫; 塩川 佳伸*; 太田 有基*; et al.

Journal of the Physical Society of Japan, 78(11), p.114704_1 - 114704_10, 2009/11

 被引用回数:10 パーセンタイル:56.85(Physics, Multidisciplinary)

We studied the magnetic properties of a paramagnet $$beta$$-US$$_2$$ with the orthorhombic crystal structure by measuring the magnetization, magnetic susceptibility, specific heat and electrical resistivity under magnetic field and pressure. The 5$$f$$-crystalline electric field (CEF) scheme was determined from the experimental results The insulating resistivity is drastically changed to a metallic one under high pressure 8 GPa similar to that of the semimetallic Ising-type ferromagnet UTeS with the Curie temperature $$T_{rm C}$$=87 K. From these experimental results, it was concluded that $$beta$$-US$$_2$$ is in the vicinity of the ferromagnetic ordering at ambient pressure. The anomalous magnetization was analyzed on the basis of the ferromagnetic cluster and discussed from a viewpoint of the magnetic polaron.


Longitudinal spin density wave order in a quasi-1D Ising-like quantum antiferromagnet

木村 尚次郎*; 松田 雅昌; 益田 隆嗣*; 本堂 英*; 金子 耕士; 目時 直人; 萩原 政幸*; 竹内 徹也*; 奥西 巧一*; He, Z.*; et al.

Physical Review Letters, 101(20), p.207201_1 - 207201_4, 2008/11

 被引用回数:41 パーセンタイル:84.37(Physics, Multidisciplinary)


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