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論文

Ultrasound-assisted removal of contaminants on stainless steel surfaces using nitrogen ultrafine bubble water

中原将海; 渡部創; 木村修也; 佐々木美咲*; 稲垣博光*; 森口哲次*

Progress in Nuclear Energy, 172, p.105195_1 - 105195_8, 2024/07

https://doi.org/10.1016/j.pnucene.2024.105195

原子力施設の廃止措置に伴い発生する二次廃棄物の低減を目指したウルトラファインバブルを用いた新しい固体汚染物質の除去技術を提案している。非放射性物質であるCo酸化物の模擬汚染物を用いた除去試験により除去技術の性能評価を実施した。また、放射性物質で汚染された燃料ピン端栓部を使用した除染試験をホットセルで実施し、異なる化学形の違いによる影響を調べた。

論文

Magnetic and transport properties of the pseudobrookite Al $_{1-x}$ Ti $_{2+x}$ O $_{5}$ single crystals

高濱隆成*; 有薗実駿*; 犬童代梧*; 吉永汰正*; 寺倉千恵子*; 竹下直*; 白崎巧*; 野田正亮*; 桑原英樹*; 梶本亮一; et al.

JPS Conference Proceedings (Internet), 38, p.011114_1 - 011114_6, 2023/05

https://doi.org/10.7566/JPSCP.38.011114

We investigated the transport and magnetic properties of single crystals of the pseudobrookite Al $_{1-x}$ Ti $_{2+x}$ O $_{5}$ for grown using a floating zone. We found a correlation of spin-singlet Ti $^{3+}$ -Ti $^{3+}$ dimers even in the conductive and phases which develops with increasing . The development of the dimer correlation suppresses the magnetic susceptibility at the low temperature and enhances the electric conductivity perhaps due to the suppression of the magnetic scattering at the isolated Ti $^{3+}$ ions. The compound shows the best conductivity in the phase near the phase boundary between the and phases where the dimer correlation is much developed. Some exotic conductive state may be realized under the background of fluctuation of the spin-singlet dimer in the phase near the phase boudary.

論文

Laser heating induced spatial homogenization of phase separated Na $_{2}$ O-B $_{2}$ O $_{3}$ -SiO $_{2}$ glass plate with bearing NiO for heat center and structural probe

富田夏奈*; 岸哲生*; 松村大樹; 矢野哲司*

Journal of Non-Crystalline Solids, 597, p.121891_1 - 121891_10, 2022/12

https://doi.org/10.1016/j.jnoncrysol.2022.121891

被引用回数：1 パーセンタイル：13.38(Materials Science, Ceramics)

Na $_{2}$ O-B $_{2}$ O $_{3}$ -SiO $_{2}$ glass plate phase separated in spinodal was partially remelted and homogenized by laser heating. As heat generation source, 0.8 mol% NiO was added to absorb continuous-wave laser with =1064 nm. After acid leaching, borate phase with NiO was remaining partially in laser irradiated area. X-ray Absorption Fine Structure (XAFS) spectra revealed that Ni $^{2+}$ in laser irradiated area showed coordination change from 6 coordinated octahedral to 5 coordinated in square pyramid along with apparent color change from green to brown. Similar change was observed in water-quenched specimen from 1000 $^{circ}$ C. Ni $^{2+}$ transition gave additional structural information in phase separate / homogeneous glass, which was difficult to be distinguished by spectroscopy which focuses on covalent bonding of glass network.

論文

Determination of $^{135}$ Cs/ $^{137}$ Cs isotopic ratio in soil collected near Fukushima Daiichi Nuclear Power Station through mass spectrometry

島田亜佐子; 塚原剛彦*; 野村雅夫*; Kim, M. S.*; 島田太郎; 武田聖司; 山口徹治

Journal of Nuclear Science and Technology, 58(11), p.1184 - 1194, 2021/11

https://doi.org/10.1080/00223131.2021.1931520

被引用回数：5 パーセンタイル：64.12(Nuclear Science & Technology)

土壌中の主要元素や質量分析における妨害元素を含む多元素混合溶液を用いて土壌中のCsを分離精製するためのCalix[4]arene-bis(t-octylbenzo-crown-6)(BOBCalixC6)の1-オクタノール溶液による溶媒抽出法を最適化した。一部のKやMo, Sn, SbがCsと共に有機相に抽出されたが、0.5M硝酸により逆抽出された。一方、抽出されたCsは0.5M硝酸ではほとんど逆抽出されないため、分離が改善された。抽出されたCsの回収は温度を323Kまで上げ、有機相を3倍量の1-ドデカノールで希釈することで達成された。開発した手法を40gの土壌を溶解した硝酸溶液に対して適用し、分離精製・濃縮後の溶液中には土壌の主要元素が合計で10g/ml、妨害元素はng/ml以下しか含まれないことを確認した。さらに、この手法を用いて福島第一原子力発電所(FDNPS)周辺で採取された土壌中のCsを分離し、 $^{135}$ Cs/ $^{137}$ Cs同位体比を表面電離型質量分析計(TIMS)とトリプル四重極質量分析計(ICP-QQQ)により分析した。TIMSにより1桁ほど高い精度が得られたが、アバンダンス感度はICP-QQQの方が高かった。FDNPSの北西側の試料に対してわずかに高い $^{135}$ Cs/ $^{137}$ Cs同位体比が観測されたが、それ以外の地点では誤差の範囲で同じ同位体比が得られた。この結果は報告されている $^{134}$ Cs/ $^{137}$ Csの放射能比の分布と一致しており、 $^{135}$ Cs/ $^{137}$ Cs同位体比が放射性セシウムの起源を特定できる可能性を示している。

論文

Structural significance of nickel sites in aluminosilicate glasses

門力也*; 岸哲生*; Lelong, G.*; Galoisy, L.*; 松村大樹; Calas, G.*; 矢野哲司*

Journal of Non-Crystalline Solids, 539, p.120070_1 - 120070_8, 2020/07

https://doi.org/10.1016/j.jnoncrysol.2020.120070

被引用回数：5 パーセンタイル：27.95(Materials Science, Ceramics)

We use Ni ions as a structural probe to investigate the influence of modifier cations on the structure of aluminosilicate glasses. The color of these glasses varies with the nature of the cations present in glass. Structural origin of this change is investigated by optical absorption and X-ray absorption spectroscopies. Our results reveal pronounced changes in Ni coordination. Tetrahedra Ni $^{2+}$ ins present in all these glasses and Ni $^{2+}$ in 5-fold coordination site also appears. There is a weak contribution from octahedral Ni $^{2+}$ . The concentration of tetrahedral Ni $^{2+}$ deduced from the optical absorption spectroscopy increases with decreasing cation field strength, explaining the variation of color from yellow and brown to purple. This is in line with X-ray absorption spectroscopy data. Cation-oxygen distances and site symmetry indicate a similar structural behavior of Mg $^{2+}$ and Ni $^{2+}$ , being a good structural probe to Mg.

論文

Structural, magnetic, transport, and thermoelectric properties of the pseudobrookite AlTi $_{2}$ O $_{5}$ -Ti $_{3}$ O $_{5}$ system

高濱隆成*; 石井透依*; 犬童代梧*; 有薗実駿*; 寺倉千恵子*; 十倉好紀*; 竹下直*; 野田正亮*; 桑原英樹*; 斎木琢夫*; et al.

Physical Review Materials (Internet), 4(7), p.074401_1 - 074401_11, 2020/07

https://doi.org/10.1103/PhysRevMaterials.4.074401

被引用回数：10 パーセンタイル：43.3(Materials Science, Multidisciplinary)

We investigated the structural, magnetic, transport, and high-temperature thermoelectric properties of single crystals of the pseudobrookite Al $_{1-x}$ Ti $_{2+x}$ O $_{5}$ for grown using a floating zone. We found a correlation of spin-singlet Ti $^{3+}$ -Ti $^{3+}$ dimers coupled with the lattice even in the conductive and phases which develops with increasing . This developing dimer correlation reduces the number of unpaired Ti $^{3+}$ ions, which makes the compound more conductive owing to the suppression of disorder for up to about 0.75. The dimer fluctuation causes a critical enhancement of the magnetic susceptibility at around 150 K in the phase near the boundary () between the and the phases. Such a correlation of the spin-singlet Ti $^{3+}$ -Ti $^{3+}$ dimers may produce a high Seebeck coefficient in the conductive and phases leading to a large thermoelectric power factor at high temperatures.

論文

STRAD project for systematic treatments of radioactive liquid wastes generated in nuclear facilities

渡部創; 小木浩通*; 荒井陽一; 粟飯原はるか; 高畠容子; 柴田淳広; 野村和則; 神谷裕一*; 浅沼徳子*; 松浦治明*; et al.

Progress in Nuclear Energy, 117, p.103090_1 - 103090_8, 2019/11

AA2019-0193.pdf:1.29MB

https://doi.org/10.1016/j.pnucene.2019.103090

被引用回数：12 パーセンタイル：79.53(Nuclear Science & Technology)

A new collaborative research project for systematic treatments of radioactive liquid wastes containing various reagents generating in nuclear facilities was started from 2018 initiated by Japan Atomic Energy Agency. The project was named as STRAD (Systematic Treatments of RAdioactive liquid wastes for Decommissioning) project. Tentative targets to be studied under the project are aqueous and organic liquid wastes which have been generated by experiments and analyses in a reprocessing experimental laboratory of JAEA. Currently fundamental studies for treatments of the liquid wastes with complicated compositions are underway. In the STRAD project, process flow for treatment of ammonium ion involved in aqueous waste was designed though the inactive experiments, and decomposition of ammonium ion using catalysis will be carried out soon. Adsorbents for recovery of U and Pu from spent solvent were also developed. Demonstration experiments on genuine spent solvent is under planning.

論文

Elastic and dynamical structural properties of La and Mn-doped SrTiO $_{3}$ studied by neutron scattering and their relation with thermal conductivities

梶本亮一; 中村充孝; 村井直樹; 社本真一; 本田孝志*; 池田一貴*; 大友季哉*; 畑博人*; 江藤貴弘*; 野田正亮*; et al.

Scientific Reports (Internet), 8(1), p.9651_1 - 9651_8, 2018/06

https://doi.org/10.1038/s41598-018-27984-z

被引用回数：6 パーセンタイル：30.02(Multidisciplinary Sciences)

The electron-doped SrTiO $_{3}$ exhibits good thermoelectric properties, which makes this material a promising candidate of an n-type oxide thermoelectric device. Recent studies indicated that only a few percent co-doping of La and Mn in SrTiO $_{3}$ substantially reduces the thermal conductivity, thereby greatly improving the thermoelectric figure of merit at room temperature. Our time-of-flight neutron scattering studies revealed that by doping both La and Mn into SrTiO $_{3}$ , the inelastic scattering spectrum shows a momentum-independent increase in the low-energy spectral weight approximately below 10 meV. The increase in the low-energy spectral weight exhibits a clear correlation with thermal conductivity. The correlation is attributed to dynamical and local structural fluctuations caused by the Jahn-Teller instability in Mn $^{3+}$ ions coupled with the incipient ferroelectric nature of SrTiO $_{3}$ , as the origin of the low thermal conductivity.

論文

3次元輸送計算コードMCNPを用いた森林除染による空間線量率の低減効果の検討

邉見光; 山口徹治; 武田聖司; 木村英雄

原子力バックエンド研究(CD-ROM), 24(1), p.3 - 14, 2017/06

https://doi.org/10.3327/jnuce.24.1_3

福島第一原子力発電所の事故起源の放射性セシウムにより汚染された森林の除染に関して、居住区域における空間線量率の低減が顕著になる汚染源の条件や除染の範囲を感度解析によって検討した。汚染源を $^{134}$ Csおよび $^{137}$ Csを含む堆積有機物層(A $_{0}$ 層)と表層土(A $_{1}$ 層)とし、モンテカルロ法による3次元輸送計算コードMCNPを用いて空間線量率を算出した。森林斜面の数、角度、汚染の分布状態、森林土壌中の放射性セシウムの量、除染範囲、林縁から評価点までの距離、評価点の高さをパラメーターとした。その結果、汚染の分布が均一の場合、林縁から20mまでのA $_{0}$ 層の除染が、空間線量率の低減に効果的であることがわかった。一方、林縁から20m以遠の汚染が20m以内よりも高いような、汚染の分布が不均一の場合、A $_{1}$ 層に比べA $_{0}$ 層に含まれる放射性セシウムの量が多い条件においてのみ、林縁から40mまでのA $_{0}$ 層の除染により、空間線量率が顕著に低減した。

論文

Effects of Mn substitution on the thermoelectric properties and thermal excitations of the electron-doped perovskite Sr $_{1-x}$ La $_{x}$ TiO $_{3}$

奥田哲治*; 畑博人*; 江藤貴弘*; 草原彰吾*; 小田涼佑*; 梶創揮*; 仁科康佑*; 桑原英樹*; 中村充孝; 梶本亮一

Journal of the Physical Society of Japan, 85(9), p.094717_1 - 094717_6, 2016/09

https://doi.org/10.7566/JPSJ.85.094717

被引用回数：5 パーセンタイル：39.89(Physics, Multidisciplinary)

We studied how Mn substitution affects the thermoelectric properties and thermal excitations of the electron-doped perovskite Sr $_{1-x}$ La $_{x}$ TiO $_{3}$ by measuring its electrical and thermal transport properties, magnetization, specific heat, and inelastic neutron scattering. Slight Mn substitution with the lattice defects enhanced the Seebeck coefficient, perhaps because of coupling between itinerant electrons and localized spins or between itinerant electrons and local lattice distortion around Mn $^{3+}$ ions, while it enhanced anharmonic lattice vibrations, which effectively suppressed thermal conductivity in a state of high electrical conductivity. Consequently, slight Mn substitution increased the dimensionless thermoelectric figure of merit for Sr $_{1-x}$ La $_{x}$ TiO $_{3}$ near room temperature.

論文

Development of spin correlations in the geometrically frustrated triangular-lattice Heisenberg antiferromagnet CuCrO

梶本亮一; 富安啓輔*; 中島健次; 河村聖子; 稲村泰弘; 奥田哲治*

Journal of the Physical Society of Japan, 84(7), p.074708_1 - 074708_6, 2015/07

https://doi.org/10.7566/JPSJ.84.074708

被引用回数：9 パーセンタイル：55.76(Physics, Multidisciplinary)

Magnetic excitations in the triangular-lattice Heisenberg antiferromagnet CuCrO $_{2}$ were studied using single-crystal inelastic neutron scattering. A diffusive quasielastic component that persisted without developing a correlation length over a wide temperature range both below and above the ordering temperature was observed. Furthermore, characteristic momentum dependence was observed that was reproduced using minimum spin clusters. The robust spin clusters contrast with conventional magnetic ordering and may be universal in triangular-lattice Heisenberg antiferromagnets.

論文

Effects of Mn substitution on the thermoelectric properties of the electron-doped perovskite Sr $_{1-x}$ La $_{x}$ TiO $_{3}$

奥田哲治*; 畑博人*; 江藤貴弘*; 仁科康佑*; 桑原英樹*; 中村充孝; 梶本亮一

Journal of Physics; Conference Series, 568(Part 2), p.022035_1 - 022035_5, 2014/12

https://doi.org/10.1088/1742-6596/568/2/022035

被引用回数：8 パーセンタイル：91.23(Physics, Applied)

We have tried to improve the n-type thermoelectric properties of the electron-doped Perovskite Sr $_{1-x}$ La $_{x}$ TiO $_{3}$ by a Mn substitution. The 1-2% Mn substitution enhances the Seebeck coefficient () and reduces the thermal conductivity () by about 50% at room temperature (RT) without largely increasing the resistivity for the 5% electron-doped SrTiO $_{3}$ . Consequently, the power factor at RT keeps a large value comparable to that of Bi $_{2}$ Te $_{3}$ and the dimensionless figure-of-merits at RT increases twofold by the slight Mn substitution. Such a large reduction of at RT is perhaps due to the effect of Jahn-Teller active Mn $^{3+}$ ions, around which dynamical local lattice distortion may occur.

論文

An Attempt to select thermodynamic data and to evaluate the solubility of radioelements with uncertainty under HLW disposal conditions

山口徹治; 武田聖司; 西村優基; 飯田芳久; 田中忠夫

Radiochimica Acta, 102(11), p.999 - 1008, 2014/11

https://doi.org/10.1515/ract-2014-2248

http://www.degruyter.com/view/j/ract.2014.102.issue-11/ract-2014-2248/ract-2014-2248.xml?format=INT

被引用回数：1 パーセンタイル：8.82(Chemistry, Inorganic & Nuclear)

熱力学データを不確実さとともに選定し、放射性元素の溶解度を地下水化学組成の変動を考慮して、不確実さとともに評価することを試みた。熱力学データは2012年に公開されたJAEA-TDBをレビューすることにより選定した。Nb, Pd, Paのデータは、データ選定プロセスの整合性の観点で見直した。Se, U, Paのデータは溶解度評価の保守性の観点で見直した。Zr, Th, U, Np, Puについては近年報告されたCa-metal(IV)-OH 3元錯体のデータを採用した。モンテカルロ法を用いて確率論的に溶解度を解析するコードPA-SOLを用いて、溶解度の確率論的解析を行った。

論文

Low-energy spin fluctuations in CuCrO $_{2}$ and Cu $_{0.85}$ Ag $_{0.15}$ CrO $_{2}$ studied by inelastic neutron scattering

梶本亮一; 中島健次; 河村聖子; 稲村泰弘; 奥田哲治*; 富安啓輔*

JPS Conference Proceedings (Internet), 3, p.014018_1 - 014018_5, 2014/06

https://doi.org/10.7566/JPSCP.3.014018

Two-dimensional triangular-lattice Heisenberg antiferromagnet (TLHA) is one of the simplest examples of the geometrical frustration, where nontrivial spin states are expected due to the frustration. CuCrO $_{2}$ is one of the TLHAs where the = 3/2 spins of Cr $^{3+}$ ions form the triangular-lattice. The spins show a three-dimensional ordering with a proper screw structure below = 24 K. To find nontrivial spin fluctuations in addition to the conventional spin wave, we have studied the magnetic excitations by inelastic neutron scattering using the chopper spectrometer AMATERAS at J-PARC. We found that the excitation spectrum shows an additional diffusive quasielastic component at temperatures ('s) slightly below and . This diffuse scattering shows the different dependence from that of the spin wave excitations, as well as a characteristic dependence. We argue the origin of the diffuse scattering in terms of the -vortex and spin molecules.

論文

Characterization of monolayer oxide formation processes on high-index Si surface by photoelectron spectroscopy with synchrotron radiation

安部壮祐*; 大野真也*; 兼村瑠威*; 吉越章隆; 寺岡有殿; 尾形祥一*; 安田哲二*; 田中正俊*

Applied Physics Express, 6(11), p.115701_1 - 115701_4, 2013/11

https://doi.org/10.7567/APEX.6.115701

被引用回数：4 パーセンタイル：18.28(Physics, Applied)

Thermal oxidation of high-index silicon surfaces, Si(113), Si(331) and Si(120) in a monolayer regime has been investigated by X-ray photoelectron spectroscopy (XPS) with synchrotron radiation. The oxide thickness, composition and band bending are evaluated by peak deconvolution of the Si 2p core level XPS spectra. We found that changes in the oxide composition correlate with changes in the band bending. This reveals that production of the Si $^{4+}$ state is associated with the Si ejection process accompanied by the production of vacancies. We found that reactivity of the Si(120) surface in oxidation is drastically reduced at reaction temperatures below 690 K.

論文

Effects of Mg, Ag, and Al substitutions on magnetic excitations in the triangular-lattice antiferromagnet CuCrO $_{2}$

梶本亮一; 中島健次; 河村聖子; 稲村泰弘; 加倉井和久; 外園貴久*; 大園怜*; 奥田哲治*

Journal of the Physical Society of Japan, 82(5), p.054702_1 - 054702_6, 2013/05

https://doi.org/10.7566/JPSJ.82.054702

被引用回数：5 パーセンタイル：38.94(Physics, Multidisciplinary)

Magnetic excitations in CuCrO $_{2}$ , CuCr $_{0.97}$ Mg $_{0.03}$ O $_{2}$ , Cu $_{0.85}$ Ag $_{0.15}$ CrO $_{2}$ , and CuCr $_{0.85}$ Al $_{0.15}$ O $_{2}$ have been studied by powder inelastic neutron scattering to elucidate the element substitution effects on spin dynamics in the Heisenberg triangular-lattice antiferromagnet CuCrO $_{2}$ . We found a variety of changes in the magnetic excitation spectra caused by the different types of the element substitutions. We argued that the origins of these changes in the magnetic excitations are the effects of doped holes or the change in dimensionality in magnetic correlations.

論文

Deep-sea record of impact apparently unrelated to mass extinction in the Late Triassic

尾上哲治*; 佐藤保奈美*; 中村智樹*; 野口高明*; 日高義浩*; 白井直樹*; 海老原充*; 大澤崇人; 初川雄一; 藤暢輔; et al.

Proceedings of the National Academy of Sciences of the United States of America, 109(47), p.19134 - 19139, 2012/11

https://doi.org/10.1073/pnas.1209486109

被引用回数：40 パーセンタイル：72.55(Multidisciplinary Sciences)

日本の上部三畳系深海底堆積物から、天体衝突の証拠である「Niに富むマグネタイト粒子」、「スフェルール」、「白金族元素異常」を報告した。特に白金族元素のひとつであるイリジウムは41.5ppbという高い値を示し、恐竜の絶滅で有名な白亜紀/古第三紀(K/Pg)境界に匹敵する異常値であることが示された。堆積物中に含まれる微化石(放散虫、コノドント)の検討から、天体衝突の起こった年代は三畳紀後期ノーリアン中期(約2億12001600万年前)であることが明らかになった。この時代は天体衝突クレーターが数多く報告されている時代として知られており、カナダのManicouaganクレーター(直径100km)が本研究で発見した天体衝突イジェクタ層を形成したクレーターとして可能性が高いと考えられる。本発見を契機として、今後世界各地のノーリアン中期の地層から、Manicouaganクレーターに由来すると思われる天体衝突の証拠が見つかると考えられる。

論文

High-pressure study of ScH $_{3}$ ; Raman, infrared, and visible absorption spectroscopy

久米徹二*; 大浦裕之*; 竹市知生*; 大村彩子*; 町田晃彦; 綿貫徹; 青木勝敏; 佐々木重雄*; 清水宏晏*; 竹村謙一*

Physical Review B, 84(6), p.064132_1 - 064132_7, 2011/08

https://doi.org/10.1103/PhysRevB.84.064132

被引用回数：19 パーセンタイル：61.17(Materials Science, Multidisciplinary)

ScH $_{3}$ の圧力誘起構造及び電子転移を調べるため、ラマン,赤外・可視光吸収スペクトルを室温下、50GPaまで観測した。hcp-中間相と中間相-fcc転移がそれぞれ25GPaと46GPaで観測された。中間相の構造はYH $_{3}$ で報告されている長周期構造と同じと思われる。ScH $_{3}$ の光学ギャップは1.7eVから減少し、50GPa付近でfcc構造への転移を伴って閉じる。

論文

Effect of spin dilution on the magnetic state of delafossite CuCrO $_{2}$ with an = 3/2 antiferromagnetic triangular sublattice

奥田哲治*; 宇都数馬*; 関真一郎*; 小野瀬佳文*; 十倉好紀*; 梶本亮一; 松田雅昌*

Journal of the Physical Society of Japan, 80(1), p.014711_1 - 014711_7, 2011/04

https://doi.org/10.1143/JPSJ.80.014711

被引用回数：26 パーセンタイル：76.16(Physics, Multidisciplinary)

We investigated an effect of spin dilution on the magnetic and thermal properties of delafossite CuCrO $_{2}$ having an = 3/2 antiferromagnetic triangular lattice (ATL) by the substitution of Al $^{3+}$ for Cr $^{3+}$ by measurements of magnetization, specific heat, and neutron scattering. Spin defects introduced into Cr ATL layers blur the antiferromagnetic transition and induce a dimensional crossover of low-energy magnetic excitation in the residual Cr ATL region due to the reduction of inter-layer magnetic interaction, while accompanying an enhancement of a spin-glass component. The observed $T^{2}$ contribution to the low- $C_mathrm{mag}$ above = 0.15, as well as in Cu $_{0.85}$ Ag $_{0.15}$ CrO $_{2}$ , comes mainly from a short-range 2D AF excitation originating in a nontrivial magnetic state such as spin-nematic or spin-liquid states.

論文

Temperature and Ag doping effect on magnetic excitations in the quasi-two-dimensional triangular lattice antiferromagnet CuCrO studied by inelastic neutron scattering

梶本亮一; 中島健次; 河村聖子; 稲村泰弘; 加倉井和久; 新井正敏; 外園貴久*; 大園怜*; 奥田哲治*

Journal of the Physical Society of Japan, 79(12), p.123705_1 - 123705_4, 2010/12

https://doi.org/10.1143/JPSJ.79.123705

被引用回数：21 パーセンタイル：71.73(Physics, Multidisciplinary)

We have studied magnetic excitations in quasi two-dimensional triangular lattice antiferromagnets CuCrO and Cu $_{0.85}$ Ag $_{0.15}$ CrO by inelastic neutron scattering. CuCrO $_{2}$ has two types of magnetic excitations: the one is highly dispersive, while the other is less dispersive and spreads over a wide range. With increasing the temperature, the weight of the latter component transfers to a lower energy, and the spin dynamics becomes a mixture of disordered spin wave and another diffusive component. The Ag doping induces similar spin dynamics even at 5 K. This manifests the impact of the Ag doping on the magnetic correlations and gives a clue to understand the unconventional spin state in the Ag doped CuCrO $_{2}$ .