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論文

M$"o$ssbauer and magnetic study of neptunyl(+1) complexes

中本 忠宏*; 中村 彰夫; 竹田 満洲雄*

M$"o$ssbauer Spectroscopy; Applications in Chemistry, Biology, and Nanotechnology, p.95 - 114, 2013/10

https://doi.org/10.1002/9781118714614.ch05

From the middle of 1990s, the $$^{237}$$Np M$"o$ssbauer and magnetic study on neptunyl(+1, +2) complexes has started at Japan Atomic Energy Research Institute (the present Japan Atomic Energy Agency). The studies of our group have revealed that, through unique interplay of strong uniaxial electric field of the yl-oxygens and the strong spin-orbit coupling of the 5f-electron systems, they exhibit intriguing common feature as an Ising-type neptunyl(+1)-molecular magnet and yet diverse character depending on the specific neptunyl(+1) CCB network structure from a Curie-para- to ferro- and meta-magnets. In this chapter, a part of our studies, especially for $$^{237}$$Np M$"o$ssbauer and magnetic study of neptunyl(+1) complexes, is reviewed.

論文

Lanthanides ($$^{151}$$Eu and $$^{155}$$Gd)-M$"o$ssbauer spectroscopic study of defect-fluorite oxides coupled with new defect crystal chemistry model

中村 彰夫; 井川 直樹; 岡本 芳浩; 日夏 幸雄*; Wang, J.*; 高橋 正*; 竹田 満洲雄*

M$"o$ssbauer Spectroscopy; Applications in Chemistry, Biology, and Nanotechnology, p.71 - 94, 2013/10

https://doi.org/10.1002/9781118714614.ch04

Some latest coupled-analysis results of lanthanides (Lns) ($$^{151}$$Eu and $$^{155}$$Gd)-M$"o$ssbauer structure and XRD lattice-parameter (a$$_{0}$$) data of defect-fluorite (DF) oxides with the new defect-crystal-chemistry (DCC) a$$_{0}$$ model have been presented. This is thus the first report of our ongoing efforts to further elaborate the DCC model and extend its applicability to more various systems including pyrochlore (P)-type stabilized zirconias and stabilized hafnias.

論文

Defect-fluorite oxides; Ln (Eu and Gd) M$"o$ssbauer study coupled with new defect-crystal-chemistry model

中村 彰夫; 井川 直樹; 岡本 芳浩; Wang, J.*; 日夏 幸雄*; 高橋 正*; 竹田 満洲雄*

Hyperfine Interactions, 217(1-3), p.17 - 26, 2013/04

https://doi.org/10.1007/s10751-012-0654-z
 被引用回数：1 パーセンタイル：52.83(Physics, Atomic, Molecular & Chemical)

To gain further insight into the controversial defect structure of so-called defect-fluorite (DF)-type oxide solid solutions (ss), MO$$_{2}$$-LnO$$_{1.5}$$ (M$$^{4+}$$= Zr, Hf, Ce, Th, U, Pu, etc; Ln$$^{3+}$$=lanthanide) we have conducted their comprehensive Ln (Eu and Gd) M$"o$ssbauer, EXAFs and NMR etc spectroscopic and XRD study freshly combined with a new defect-fluorite-chemistry model recently proposed by one (AN) of the present authors. In this talk some latest achievements of this study is described and discussed.

論文

欠陥蛍石型酸化物; 構造,物性及び応用; 新しい欠陥結晶化学モデルと結びつけたメスバウアー, EXAFS及びNMR研究

中村 彰夫

メスバウアー分光研究, (14), p.8 - 11, 2013/00

最近、一連の欠陥蛍石型酸化物、MO$$_{2}$$-LnO$$_{1.5}$$系(M$$^{4+}$$=Ce, Th, Zr, Hf, U等; Ln$$^{3+}$$=3価ランタノイド)の格子定数の非ヴェガード性と非ランダムな欠陥構造を統一的に記述する新しい欠陥結晶化学モデルを提案した。本講演では、その概要を、その発想のもととなりまたこれを裏付けると思われる微視的なメスバウアー, EXAFS及びNMRによる局所構造データ並びにこれらの系の実際的応用との関連において、紹介する。

論文

Single crystal growth and magnetic anisotropy of hexagonal PuGa$$_{3}$$

芳賀 芳範; 本間 佳哉*; 青木 大*; 中島 邦久; 荒井 康夫; 松田 達磨; 池田 修悟*; 酒井 宏典; 山本 悦嗣; 中村 彰夫; et al.

Journal of the Physical Society of Japan, 81(Suppl.B), p.SB007_1 - SB007_4, 2012/12

https://doi.org/10.1143/JPSJS.81SB.SB007
 被引用回数：0 パーセンタイル：0(Physics, Multidisciplinary)

We report recent progresses in single crystal preparation as well as physical properties of actinide intermetallic compounds. Flux techniques have successfully been applied for obtain- ing new compounds, including the heavy fermion superconductor NpPd$$_5$$Al$$_2$$ and related compounds. For plutonium compounds, where the radiation damage due to the $$alpha$$-decay of $$^{239}$$Pu is significant, a synthesis technique using the less-radioactive $$^{242}$$Pu isotope has been developed.

論文

$$^{155}$$Gd M$"o$ssbauer spectroscopic and powder X-ray diffraction study of CeO$$_{2}$$ - GdO$$_{1.5}$$ solid solution

中村 彰夫; 今井 和貴*; 井川 直樹; 岡本 芳浩; 山本 悦嗣; 松川 史郎*; 高橋 正*

Hyperfine Interactions, 207(1-3), p.67 - 71, 2012/03

https://doi.org/10.1007/s10751-011-0419-0
 被引用回数：4 パーセンタイル：87.07(Physics, Atomic, Molecular & Chemical)

Powder X-ray diffractometry and $$^{155}$$Gd-M$"o$ssbauer spectroscopy have been applied to the Ce$$_{1-y}$$Gd$$_{y}$$O$$_{2-y/2}$$ prepared at 1450$$^{circ}$$C. The former shows that this system forms a complete solid solution being the disordered defect-fluorite type in the smaller y range than 0.30 and the order C-type beyond y = 0.30. Its marked positive non-Vegardianity was consistently interpreted as a generalized Vegard-law behaviour of this distortion-dilated solid solution having Gd$$^{3+}$$ - oxygen vacancy association. The latter also clarifies that in the ordered C-type phase with decreasing y the 8b-site $$^{155}$$Gd-M$"o$ssbauer intensity steadily diminishes and vanishes at y = 0.50, indicating that the more-distorted minor 8b Gd$$^{3+}$$ in C-type GdO$$_{1.5}$$ is being preferentially replaced with Ce$$^{4+}$$.

論文

Irradiation history of Itokawa regolith material deduced from noble gases in the Hayabusa samples

長尾 敬介*; 岡崎 隆司*; 中村 智樹*; 三浦 弥生*; 大澤 崇人; 馬上 謙一*; 松田 伸太郎*; 海老原 充*; Ireland, T.*; 北島 富美雄*; et al.

Science, 333(6046), p.1128 - 1131, 2011/08

https://doi.org/10.1126/science.1207785
 被引用回数：130 パーセンタイル：95.22(Multidisciplinary Sciences)

はやぶさが回収した小惑星イトカワの岩石粒子中の希ガス同位体組成を測定した結果、月試料に匹敵する高い濃度の太陽風起源He, Ne, Arを確認した。これらの希ガス組成は繰り返されたインプランテーションと、イトカワ上のレゴリス粒子同士の摩擦によってHeに富んだリムの除去による選択的Heの損失によって説明可能である。イトカワ上のレゴリスの照射時間はわずか1000万年未満であり、小さな小惑星上の物質が容易に宇宙空間に散逸してしまうことを反映している。

論文

Crystal structure and physical properties of trigonal NpGa$$_3$$ and Np$$_{3}$$Ga$$_{11}$$

芳賀 芳範; 青木 大*; 本間 佳哉*; 松田 達磨; 池田 修悟*; 酒井 宏典; 山本 悦嗣; 中村 彰夫; 塩川 佳伸*; 大貫 惇睦

Journal of the Physical Society of Japan, 80(Suppl.A), p.SA109_1 - SA109_3, 2011/07

https://doi.org/10.1143/JPSJS.80SA.SA109
 被引用回数：0 パーセンタイル：0(Physics, Multidisciplinary)

We report reinvestigation the Np-Ga binary system. We successfully obtained NpGa$$_3$$ single crystals. Detailed investigation of the crystal structure using the single-crystal X-ray diffraction has shown that the flux-grown NpGa$$_3$$ crystallizes not in cubic but in the trigonal R$$overline{3}$$m structure. It orders ferromagnetically at 70 K with the saturation moment of 1.5 $$mu_{rm B}$$/Np. It is interesting to note that the cubic NpGa$$_3$$ orders antimagnetically at similar temperature 62 and become ferromagnetic under magnetic field with the similar saturation moment 1.6 $$mu_{rm B}$$/Np. These characteristics are understood from the structural point of view.

論文

New Defect-crystal-chemical approach to non-vegardianity and complex defect structure of fluorite-based MO$$_{2}$$-LnO$$_{1.5}$$ solid solutions (M$$^{4+}$$=Ce, Th; Ln$$^{3+}$$= Lanthanide), 2; Detailed local-structure and ionic-conductivity analysis

中村 彰夫

Solid State Ionics, 181(37-38), p.1631 - 1653, 2010/12

https://doi.org/10.1016/j.ssi.2010.09.022
 被引用回数：17 パーセンタイル：58.6(Chemistry, Physical)

Part I proposed a new lattice-parameter (a$$_{0}$$(ss)) model for Defect-Fluorite (DF) M$$_{1-y}$$Ln$$_{y}$$O$$_{2-y/2}$$ solid solutions (ss);this clarified their markedly non-Vegardian behavior as a macroscopic manifestation of their microscopic non-randomness represented by non-random CN(Ln$$^{3+}$$, M$$^{4+}$$) data. Part II further clarified that these CN(Ln$$^{3+}$$, M$$^{4+}$$) data can provide a quantitative description of their detailed non-random local structure such as mutually non-randomly defect (V$$_{O}$$)-coordinated cation concentrations and their intriguing ionic-conductivity behavior as a multiple V$$_{O}$$ - O$$^{2-}$$ transport process. Thus, the present model is proposed as a new quantitative a$$_{0}$$(ss) model for DF oxides and as a new direct link to their controversial defect structure. A complete description of the methodology and results of detailed local-structure and ionic-conductivity analysis is given, mainly focusing on Ce-Y.

論文

New defect-crystal-chemical approach to non-Vegardianity and complex defect structure of fluorite-based MO$$_{2}$$-LnO$$_{1.5}$$ solid solutions (M$$^{4+}$$=Ce, Th; Ln$$^{3+}$$=Lanthanide), 1; Model description and lattice-parameter data analysis

中村 彰夫

Solid State Ionics, 181(35-36), p.1543 - 1564, 2010/11

https://doi.org/10.1016/j.ssi.2010.09.019
 被引用回数：25 パーセンタイル：69.32(Chemistry, Physical)

Lattice parameter data of defect fluorite (DF) solid solutions between MO$$_{2}$$ and LnO$$_{1.5}$$ (M=Ce, Th; Ln=Y, Gd, Eu, Sm, Nd, La) exhibit marked positive deviation from Vegard law. Their detailed analysis shows that this is a generalized non-Vegardian behavior of these oxygen-vacancy (V$$_{rm O}$$) type distortionally-dilated solid solutions with non-random oxygen coordination around the cations: The M=Ce and Th shift to the opposite non-randomness for the larger Ln: strongly Ce-V$$_{rm O}$$ associative in the former and extremely Ln-V$$_{rm O}$$ associative in the latter. Given compatibility with ion-packing model, this can also provide us with their metal-oxygen bond-length data. The author describes here such random to non-random model extension and its-based main $$a$$$$_{rm 0}$$ including their comparison with reported local-structure, thermodynamic data of these systems.

論文

Magnetic and dielectric study of R$$_{0.5}$$Sr$$_{0.5}$$MnO$$_{3}$$ (R = Gd, Tb and Dy)

吉井 賢資; 平光 雄介*; 岡島 由佳*; 米田 安宏; 西畑 保雄; 水木 純一郎; 中村 彰夫; 下条 豊; 石井 慶信*; 森井 幸生; et al.

Materials Research Bulletin, 45(11), p.1574 - 1580, 2010/10

https://doi.org/10.1016/j.materresbull.2010.07.024
 被引用回数：12 パーセンタイル：37.22(Materials Science, Multidisciplinary)

R$$_{0.5}$$Sr$$_{0.5}$$MnO$$_{3}$$ (R=Gd, Tb, Dy)の磁性と誘電性を調べた。磁気測定からは、すべての系において40K以下でスピングラス的な相が観測され、中性子散乱の結果と定性的に一致した。このグラス相の起源は、R$$^{3+}$$とSr$$^{3+}$$のサイズの違いによるランダムネス効果であると考えられる。誘電率測定からは、50Kから300Kの間で5000-10000程度の誘電率が観測され、誘電率はスピングラス転移温度付近でブロードなピークとなった。誘電分散の解析からは、誘電応答の乱雑性が見いだされ、磁性の結果同様、これはR/Srサイトのランダムネスに起因すると考えた。さらに、放射光測定の結果などから、この系の誘電応答はMn-3d電子に由来することが示唆された。

論文

Magnetism and superconductivity in the new family of actinide compounds; AnPd$$_{5}$$Al$$_{2}$$

芳賀 芳範; 本間 佳哉*; 青木 大*; 池田 修悟*; 松田 達磨; 立岩 尚之; 山本 悦嗣; 中村 彰夫; 中島 健次; 荒井 康夫; et al.

IOP Conference Series; Materials Science and Engineering, 9, p.012046_1 - 012046_7, 2010/05

https://doi.org/10.1088/1757-899X/9/1/012046
 被引用回数：0 パーセンタイル：1.02(Chemistry, Inorganic & Nuclear)

It is now well recognized that 5f electrons in actinide show a variety of intriguing physical properties such as heavy fermions, various magnetic and multipolar orderings and exotic superconductivity. Particularly, superconductivity in transuranium compounds are characterized by rather higher transition temperature compared to uranium- or rare-earth-based superconductor, as well as the existence of localized-like 5f paramagnetic moments following Curie-Weiss law. Among them, NpPd$$_{5}$$Al$$_{2}$$ is the first neptunium-based heavy fermion superconductor. Detailed investigations of the magnetic and thermal properties around the upper critical field have been performed. It is shown that the large anisotropic paramagnetic moment as well as electronic specific heat existing in the normal state vanish in the superconducting state, indicating a spin-singlet pairing.

論文

Heavy fermion state and quantum criticality

大貫 惇睦; 摂待 力生*; 本多 史憲*; Dung, N. D.*; 石倉 達朗*; 竹内 徹也*; 松田 達磨; 立岩 尚之; 中村 彰夫; 山本 悦嗣; et al.

Physica B; Condensed Matter, 405(9), p.2194 - 2199, 2010/05

https://doi.org/10.1016/j.physb.2010.02.006
 被引用回数：1 パーセンタイル：6.48(Physics, Condensed Matter)

The heavy fermion state in the f-electron systems is due to competition between the RKKY interaction and the Kondo effect. To understand the electronic state, we studied the Fermi surface properties via the de Haas-van Alphen (dHvA) experiments and energy band calculations for CeSn$$_{3}$$, CeRu$$_{2}$$Si$$_{2}$$, UPt$$_{3}$$, and nowadays, transuranium compounds of NpGe$$_{3}$$ and PuIn$$_{3}$$, together with YbCu$$_{2}$$Si$$_{2}$$.

論文

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

https://doi.org/10.1143/JPSJ.78.114704
 被引用回数：12 パーセンタイル：59(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.

論文

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

https://doi.org/10.1103/PhysRevB.80.104419
 被引用回数：6 パーセンタイル：29.51(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.

論文

Hyperfine interactions in the itinerant system UFeGa$$_{5}$$

神戸 振作; 酒井 宏典; 徳永 陽; 中堂 博之; 安岡 弘志; 松田 達磨; 芳賀 芳範; 池田 修悟; 中村 彰夫; 山本 悦嗣; et al.

Journal of Nuclear Materials, 385(1), p.1 - 3, 2009/03

https://doi.org/10.1016/j.jnucmat.2008.10.030
 被引用回数：1 パーセンタイル：10.22(Materials Science, Multidisciplinary)

5f電子系では新奇な超伝導や磁性が電子相関や軌道縮退の効果で低温で見られる。例えば、われわれはNpPd$$_5$$Al$$_2$$($$T_c$$=5K)とPuRhGa$$_5$$($$T_c$$=9K)を各種測定手段で研究した。また、新奇超伝導と磁気揺らぎの関係についても考察する。それ以外には、二酸化アクチノイドAnO$$_2$$(An; U, Np, Pu, Am)も大変興味深い。$$^{17}$$O-NMRを用いて、UO$$_2$$の双極子+四極子,NpO$$_2$$の四極子+八極子を解明した。一方、PuO$$_2$$は非磁性である。このように5f電子系は低温物理学の最後の未踏領域として、魅力ある分野であるのでその展望も述べる。

論文

Crystal structure and magnetic properties of the new ternary actinide compounds AnPd$$_5$$Al$$_2$$ (An = U, Np)

芳賀 芳範; 青木 大*; 本間 佳哉*; 池田 修悟; 松田 達磨; 山本 悦嗣; 酒井 宏典; 立岩 尚之; Dung, N. D.*; 中村 彰夫; et al.

Journal of Alloys and Compounds, 464(1-2), p.47 - 50, 2008/09

https://doi.org/10.1016/j.jallcom.2007.10.037
 被引用回数：19 パーセンタイル：66.95(Chemistry, Physical)

We report the crystal structure and magnetic properties of new ternary actinide compounds UPd$$_5$$Al$$_2$$ and NpPd$$_5$$Al$$_2$$. Both compounds crystallize in the body-center tetragonal ZrAl$$_5$$Ni$$_2$$ -type tetragonal structure (I 4/mmm). Although the magnetic susceptibility of both compounds follows the Curie-Weiss behavior at high temperature, no magnetic phase transition was observed. UPd$$_5$$Al$$_2$$ has a nonmagnetic ground state where the magnetic susceptibility saturates at low temperature, while NpPd$$_5$$Al$$_2$$ superconducts below 4.9 K as reported recently.

論文

NMR investigation of quadrupole order parameter in actinide dioxides

徳永 陽; 本間 佳哉*; 神戸 振作; 青木 大*; 酒井 宏典; 中堂 博之; 生嶋 健司*; 山本 悦嗣; 中村 彰夫; 塩川 佳伸*; et al.

Journal of Optoelectronics and Advanced Materials, 10(7), p.1663 - 1665, 2008/07

アクチノイドや希土類元素を含むf電子系化合物の多様な物性の背後には、f電子が持つ多極子の自由度が隠されている。この多極子の自由度が最も顕著に現れるのが多極子秩序と呼ばれる現象である。講演ではわれわれが行った二酸化ネプツニウム単結晶を用いた核磁気共鳴研究の結果を中心に、この新奇な秩序相について紹介する。また低温の電子状態について二酸化ウラニウムや二酸化プルトニウムとの比較も行う。

論文

Pressure effect on paramagnet $$beta$$-US$$_2$$

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

Physica B; Condensed Matter, 403(5-9), p.893 - 894, 2008/04

https://doi.org/10.1016/j.physb.2007.10.059
 被引用回数：6 パーセンタイル：30.34(Physics, Condensed Matter)

斜方晶の結晶構造を持つ、常磁性半導体$$beta$$-US$$_2$$の単結晶を、化学輸送法によって育成した。これらの単結晶を用いて、圧力下電気抵抗と磁化を測定した。その結果、圧力の増加とともに電気抵抗の温度依存性は、半金属的な振る舞いに近づき、さらに$$T_{rm a}$$において、異常が観測された。この$$T_{rm a}$$は、圧力とともに、高温側へシフトする。同じ結晶構造を持つ強磁性化合物UTeSとの比較から、この$$T_{rm a}$$は、強磁性転移である可能性がある。

論文

$$^{31}$$P-NMR study of the neptunium-based filled-skutterudite NpFe$$_4$$P$$_{12}$$

徳永 陽; 青木 大*; 本間 佳哉*; 酒井 宏典; 中堂 博之; 神戸 振作; 松田 達磨; 池田 修悟; 山本 悦嗣; 中村 彰夫; et al.

Journal of the Physical Society of Japan, 77(Suppl.A), p.211 - 213, 2008/00

https://doi.org/10.1143/JPSJS.77SA.211
 被引用回数：3 パーセンタイル：27.6(Physics, Multidisciplinary)

超ウラン元素を含む初めての充填スクッテルダイト化合物NpFe$$_4$$P$$_{12}$$について行った$$^{31}$$P-NMR測定の結果について発表する。磁場角度分解NMRスペクトルの測定から明らかになったPサイトにおける超微細磁場の磁場角度依存性を報告し、以前に報告されているUFe$$_4$$P$$_{12}$$やPrFe$$_4$$P$$_{12}$$における結果との比較を行う。またスピン-格子緩和時間の測定結果も報告し、磁気励起の特性について局在f電子モデルの立場から議論を行う。

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