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論文

Dynamical quadrupole structure factor of frustrated ferromagnetic chain

大西 弘明

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

https://doi.org/10.1016/j.physb.2017.10.056
 被引用回数：2 パーセンタイル：10.21(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.

論文

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

https://doi.org/10.1016/j.physb.2017.09.085
 被引用回数：2 パーセンタイル：10.21(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.

論文

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

https://doi.org/10.1016/j.physb.2017.09.087
 被引用回数：3 パーセンタイル：15.36(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).

論文

Detailed study of the structure of the low-energy magnetic excitations in overdoped La$$_{1.75}$$Sr$$_{0.25}$$CuO$$_{4}$$

池内 和彦*; 菊地 龍弥*; 中島 健次; 梶本 亮一; 脇本 秀一; 藤田 全基*

Physica B; Condensed Matter, 536, p.717 - 719, 2018/05

https://doi.org/10.1016/j.physb.2017.11.022
 被引用回数：2 パーセンタイル：10.21(Physics, Condensed Matter)

銅酸化物高温超伝導体の過剰ドープ領域における低エネルギーの磁気励起の構造の詳細を調べるために、我々は、La$$_{1.75}$$Sr$$_{0.25}$$CuO$$_{4}$$の中性子非弾性散乱実験を行った。過去に報告されたように、非整合な磁気相関に対応した$$Q_{rm tet}$$ = (0.5 $$pm$$ $$delta$$, 0.5)/(0.5, 0.5 $$pm$$ $$delta$$)を中心とした磁気励起を明瞭に観測した。それに加えて、$$Q_{rm tet}=(0.5, 0.5)$$を中心とした円環状の励起も観測された。円環の半径($$r$$=0.109)は、磁気相関の非整合性($$delta$$=0.118)より小さい。このことは、円環状の磁気励起は非整合な磁気相関とはその原因を異にしていることを示唆している。La$$_{2-x}$$Sr$$_{x}$$CuO$$_{4}$$の磁気励起はこのように2種類の励起を持つことが示唆される。

口頭

Magnetic properties of RCrTiO$$_{5}$$ (R=rare earth elements)

安井 幸夫*; 宮本 拓馬*; 郡 俊輔*; 寺崎 一郎*; 吉澤 大智*; 赤木 暢*; 萩原 政幸*; 松川 健*; 吉田 幸彦*; 星川 晃範*; et al.

no journal, , 

RCrTiO$$_{5}$$多結晶試料について、50Tまでの磁場中における比熱および磁化を測定し、また、NdCrTiO$$_{5}$$およびNd$$_{0.5}$$Pr$$_{0.5}$$CrTiO$$_{5}$$の粉末中性子回折測定を行った。50Tまでの比熱データと磁化曲線から、Cr$$^{3+}$$-Cr$$^{3+}$$間およびCr$$^{3+}$$-R$$^{3+}$$間の磁気モーメントの磁気相互作用を評価した。また、NdCrTiO$$_{5}$$の中性子磁気反射強度の温度依存性から、Cr$$^{3+}$$モーメントとNd$$^{3+}$$モーメントが$$T_mathrm{N}$$で同時にオーダーすることが明らかとなった。本発表では、実験で得られた磁気挙動を基に、RCrTiO$$_{5}$$の磁気電気効果機構について議論する。

口頭

Electronic structures of uranium compounds studied by angle-resolved photoelectron spectroscopy

藤森 伸一

no journal, , 

Band structure and Fermi surface are fundamental information for modeling physical properties of materials. Angle-resolved photoelectron spectroscopy (ARPES) is a powerful experimental technique by which the band structures and Fermi surfaces of materials can be determined. In this presentation, I am going to review the electronic structures of strongly correlated uranium compounds studied by angle-resolved photoelectron spectroscopies with soft X-ray synchrotron radiation. We have studied the electronic structures of more than twenty uranium compounds including itinerant compounds, heavy Fermions, and localized compounds.

口頭

Spin state of superconducting URu$$_2$$Si$$_2$$ probed by $$^{29}$$Si Knight shift

服部 泰佑; 酒井 宏典; 徳永 陽; 神戸 振作; 松田 達磨*; 芳賀 芳範

no journal, , 

重い電子系ウラン化合物URu$$_2$$Si$$_2$$は、17.5Kでいわゆる「隠れた秩序」状態に相転移し、1.5Kで超伝導を示す。「隠れた秩序」解明に向けて多くの研究がなされているが、隠れた秩序下で生じる超伝導の発現機構や、両秩序間の関係も興味深い課題である。非常に狭い線幅の$$^{29}$$Si NMRスペクトルにより達成した高解像度ナイトシフト測定で得た超伝導状態におけるスピン状態について報告する。

口頭

Lifetime of antiferromagnetic spinwave due to electrons correlation

森 道康

no journal, , 

We have study the bilayer system of an AF insulator (Mott insulator) and a correlated metal, in which the double occupancy is forbidden. The self-energy of antiferromagnetic magnon in the Mott insulator is calculated in the second order of a magnetic interlayer coupling. The Gutzwiller approximation is used to include electrons correlation in the correlated metal. We find that the lifetime of antiferromagnetic magnon in the Mott insulator is greatly supressed by the electrons correlation in the correlated metal.

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