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論文

Ferroaxial transitions in glaserite-type compounds; Database screening, phonon calculations, and experimental verification

山岸茂直*; 林田健志*; 三澤龍介*; 木村健太*; 萩原雅人; 村田智城*; 廣瀬左京*; 木村剛*

Chemistry of Materials, 35(2), p.747 - 754, 2023/01

https://doi.org/10.1021/acs.chemmater.2c03540

被引用回数：5 パーセンタイル：91.39(Chemistry, Physical)

The so-called "ferroaxial transition" characterized by a rotational structural distortion that breaks a mirror symmetry has gained growing interest in terms of a new class of ferroic state in crystalline materials. RbFe(MoO $_{4}$ ) $_{2}$ which belongs to glaserite-type compounds, X□;1 Y□;2 [M(TO $_{4})_{2}$ ], is one of the most representative materials showing a ferroaxial transition, i.e., ferroaxial materials. Considering a variety of glaserite-type compounds, we expect that they provide a good arena for ferroaxial materials. In this work, we explored new ferroaxial materials by formula-based screening using regular expression search and symmetry detection algorithm. As a result, we found that a glaserite-type compound, K $_{2}$ Zr(PO $_{4}$ ) $_{2}$ , is one of the promising candidates for ferroaxial materials. Experimentally, we demonstrate that K $_{2}$ Zr(P O $_{4}$ ) $_{2}$ shows a ferroaxial transition at about 700 K, which is well explained by ab initio phonon calculations. The ferroaxial nature of K $_{2}$ Zr(PO $_{4}$ ) $_{2}$ is further confirmed by the observation of its domain structures using a linear electrogyration effect, that is, optical rotation in proportion to an applied electric field. Our work provides an effective approach to exploring ferroaxial materials.

論文

Phase transition and domain formation in ferroaxial crystals

林田健志*; 上村洋平*; 木村健太*; 松岡悟志*; 萩原雅人; 廣瀬左京*; 盛岡仁*; 長谷川達夫*; 木村剛*

Physical Review Materials (Internet), 5(12), p.124409_1 - 124409_10, 2021/12

https://doi.org/10.1103/PhysRevMaterials.5.124409

被引用回数：17 パーセンタイル：80.41(Materials Science, Multidisciplinary)

The ferroaxial order, which is characterized by a rotational structural distortion in a crystal, has been recently proposed as one of ferroic orders. Though the domain formation is a characteristic feature in ferroic materials, there has been little study done concerning that for the ferroaxial order. Here, we investigate ferroaxial domains that are formed through a ferroaxial transition in two representative ferroaxial materials, NiTiO $_{3}$ and RbFe(MoO $_{4}$ ) $_{2}$ . We spatially resolve their domain structures using an optical method based on electric-field- induced optical rotation, that is, electrogyration (EG). In NiTiO $_{3}$ , multi-domains are constructed when crystals undergo a ferroaxial transition and the domain size depends on the cooling rate around the transition temperature. Furthermore, the ferroaxial domain structure obtained by the EG measurement is well matched with that by scanning X-ray diffraction (XRD). RbFe(MoO $_{4}$ ) $_{2}$ also exhibits multi-domain states in which domain patterns are different each time a crystal undergoes a ferroaxial transition. In addition, the temperature dependence of the EG signal well obeys that of the order parameter of a first-order phase transition. These results ensure the effectiveness of the EG effect to elucidate the nature of ferroaxial order.

論文

Coexistence of magnetoelectric and antiferroelectric-like orders in Mn $_{3}$ Ta $_{2}$ O $_{8}$

木村健太*; 八木直輝*; 長谷川舜介*; 萩原雅人; 三宅厚志*; 徳永将史*; Cao, H.*; 益田隆嗣*; 木村剛*

Inorganic Chemistry, 60(20), p.15078 - 15084, 2021/10

https://doi.org/10.1021/acs.inorgchem.1c02461

被引用回数：1 パーセンタイル：10.45(Chemistry, Inorganic & Nuclear)

In materials showing a linear magnetoelectric (ME) effect, unconventional functionalities can be anticipated such as electric control of magnetism and nonreciprocal optical responses. Thus, the search of new linear ME materials is of interest in materials science. Here, using a recently proposed design principle of linear ME materials, which is based on the combination of local structural asymmetry and collinear antiferromagnetism, we demonstrate that an anion-deficient fluorite derivative Mn $_{3}$ Ta $_{2}$ O $_{8}$ is a new linear ME material. This is evidenced by the onset of magnetic-field-induced electric polarization in its collinear antiferromagnetic phase below $T_{rm N}$ = 24 K. Furthermore, we also find an antiferroelectric-like phase transition at $T_{rm S}$ = 55 K, which is attributable to an off-center displacement of magnetic Mn $^{2+}$ ions. The present study shows that Mn $_{3}$ Ta $_{2}$ O $_{8}$ is a rare material that exhibits both ME and antiferroelectric-like transitions. Thus, Mn $_{3}$ Ta $_{2}$ O $_{8}$ may provide an opportunity to investigate the physics associated with complicated interactions between magnetic (spin) and electric dipole degrees of freedom.

論文

Fixed point observations and characterization of radioactive caesium in Tama river

萩原健太*; 越智康太郎; 小池裕也*

Radioisotopes, 70(4), p.227 - 237, 2021/05

https://doi.org/10.3769/radioisotopes.70.227

多摩川中流域で定点観測を実施し、河川水及び底質中の放射性セシウムの挙動を2012年から2016年にかけて調査した。河川水及び底質中の放射性セシウム濃度は、時間とともに減少した。雨により水中が懸濁すると、懸濁態放射性セシウムと底質中放射性セシウムの濃度が一時的に増加した。一方、溶存態放射性セシウムはこの影響を受けなかった。底質に関して逐次抽出、元素および結晶相分析を行い、放射性セシウムの化学状態と底質への吸着メカニズムを調査した。底質中の放射性セシウムは安定した化学形態で存在しており、バイオタイトが放射性セシウムを取り込んでいる可能性があった。

論文

坑道掘削時の内空変位計測結果に基づく初期応力状態の推定

青柳和平; 亀村勝美*; 菅原健太郎*; 萩原健司*

第53回地盤工学研究発表会発表講演集(DVD-ROM), p.11 - 12, 2018/07

大規模な地下施設の設計・施工にあたっては、岩盤の不均質性を考慮して適切な初期応力状態を設定することが重要となる。幌延深地層研究センターでは、地下施設建設前のボーリング調査で水圧破砕試験により初期応力状態を設定したが、水圧破砕試験で評価できる領域は小さいため、不均質性の影響を含む広範囲な初期応力状態の設定については課題が残されていた。そこで本研究では、幌延深地層研究センターの深度350mに掘削された周回坑道で取得した内空変位に基づき、地下施設規模の初期応力状態を推定する手法を開発し、適用した。推定した初期応力値は、設計で用いた値より高い結果であるものの、ボーリング調査結果に矛盾するものではなかった。

論文

Single crystal growth and various electronic states in Yb-based compounds

広瀬雄介*; 吉内伸吾*; 西村尚人*; 阪口準也*; 榎健太郎*; 岩川健*; 三浦泰直*; 杉山清寛*; 大貫惇睦; 摂待力生*; et al.

Journal of the Korean Physical Society, 62(12), p.1858 - 1861, 2013/06

https://doi.org/10.3938/jkps.62.1858

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

We succeeded in growing single crystals of YbTIn (T: Co, Rh, Ir), YbGa, YbTZn $_{20}$ (T: Co, Rh, Ir), etc. The electronic and magnetic properties are clarified by measuring the electrical resistivity, magnetic susceptibility, magnetization, specific heat and de Haas-van Alphen effect.

論文

Spin-orbital short-range order on a honeycomb-based lattice

中辻知*; 久我健太郎*; 木村健太*; 佐竹隆太*; 片山尚幸*; 西堀英治*; 澤博*; 石井梨恵子*; 萩原政幸*; Bridges, F.*; et al.

Science, 336(6081), p.559 - 563, 2012/05

https://doi.org/10.1126/science.1212154

被引用回数：114 パーセンタイル：95.24(Multidisciplinary Sciences)

フラストレートした磁性体においても最低温度まで乱れが残る場合がある。その一例がBaCuSbOであり、微視的に見ると磁気的に非対称である一方、長さ,時間スケールともに平均的に見ると対称な状態にある。われわれは、この物質において静的なヤーンテラー歪を示すことなくCu $^{2+}$ イオンのハニカム格子が、フラストレートした状態にあることを見いだした。このハニカム格子においては、スピン1/2同士が2次元的にランダムに結合しており、スピンダイマー的なブロードな励起があり、また低エネルギーのスピン自由度が残ることが見られた。

論文

Magnetic-field-induced metallic state in -US

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

https://doi.org/10.1143/JPSJS.80SA.SA104

被引用回数：3 パーセンタイル：27.54(Physics, Multidisciplinary)

Magnetic and transport properties under high magnetic field were studied on a magnetic semiconductor -US. 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.

口頭

反強磁性体UCd $_{11}$ の磁性

山本悦嗣; 広瀬雄介*; 榎健太郎*; 三田村勝哉*; 杉山清寛*; 竹内徹也*; 萩原政幸*; 金道浩一*; 芳賀芳範; 摂待力生*; et al.

no journal, ,

UCd $_{11}$ は格子定数a=9.29のBaHg $_{11}$ 型立方晶をとり、その最近接U-U間距離は6.56と大きい。また、UCd $_{11}$ は $T_{N}$ =5Kとこの系の化合物では転移温度が高く、また常磁性領域における電子比熱係数は840mJ/Kmolと大きい。これまでに単結晶による物性測定が行われ、//100方向の磁気相図が得られている。今回新たに、UCd $_{11}$ の//100, 110, 111の1.3Kにおける強磁場磁化曲線を測定し、転移磁場及び磁場誘起強磁性相における磁気異方性を見いだした。

口頭

堆積軟岩における立坑の覆工コンクリートのひび割れ発生メカニズムと抑制

南出賢司*; 萩原健司*; 名合牧人*; 小川弘之*; 宇山幹紀*; 木須芳男*; 森本勤*; 矢吹義生*; 工藤元; 稲垣大介; et al.

no journal, ,

北海道天塩郡幌延町において建設を進めている幌延地下研究施設の立坑において、覆工コンクリートの東西方向にひび割れが発生する事象が確認されている。本発表はその覆工コンクリートのひび割れの発生メカニズムを分析した結果とこれまでに行ったひび割れ抑制対策について報告するものである。

口頭

Ferroaxial transition in the glaserite compound Na $_{2}$ BaCo(PO $_{4}$ ) $_{2}$

梶田遥一*; 山岸茂直*; 林田健志*; 木村健太*; 萩原雅人; 木村剛*

no journal, ,

Ferroaxial order is characterized by the symmetry breaking of the mirror parallel to the principal axis in the crystal structure. It is predicted to show unique physical properties such as the antisymmetric thermopolarization, that is, the induced-polarization perpendicular to the applied temperature gradient [1]. So far, materials showing ferroaxial order are limited. A recent study focused on the glaserite-type compounds belonging to the space group P-3 (No. 147) or P-3m1 (No. 164) as ferroaxial material candidates and experimentally confirmed that one of such compounds, K $_{2}$ Zr(PO $_{4}$ ) $_{2}$ is a ferroaxial material [2]. In this work, we focus on one of the glaserite-type compounds, Na $_{2}$ BaCo(PO $_{4}$ ) $_{2}$ . We synthesized polycrystalline samples by a solid-state reaction and single crystals by a flux method similar to the previous report [3]. We conducted measurements of thermogravimetry and differential thermal analysis (TG-DTA) for these samples and found the possibility that Na $_{2}$ BaCo(PO $_{4}$ ) $_{2}$ undergoes a phase transition at around 700 K. Through neutron powder diffraction measurements, we revealed that the phase transition is a ferroaxial transition from ferroaxial P-3; to nonferroaxial P-3m1. In the ferroaxial phase of Na $_{2}$ BaCo(PO $_{4}$ ) $_{2}$ , there are two domain states depending on the sign of the order parameter, which corresponds to the rotational direction of the PO $_{4}$ tetrahedron. Such domain states can be visible with the electrogyration, that is, the gyration induced by an applied electric field [4]. Using this technique, we attempted to visualize the ferroaxial domains in Na $_{2}$ BaCo(PO $_{4}$ ) $_{2}$ . In this presentation, details of the experiments and results will be presented. [1] J. Nasu and S. Hayami, Phys. Rev. B 105, 245125 (2022).[2] S. Yamagishi et al., Chem. Mater. 35, 747 (2023).[3] R. Zhong et al., Proc. Natl. Acad. Sci. USA 116, 14505 (2019).[4] T. Hayashida et al., Nat. Commun. 11, 4582 (2020).

口頭

Ferroaxial transitions in glaserite-type compounds; Database screening, phonon calculations, and experimental verification

山岸茂直*; 林田健志*; 三澤竜介*; 木村健太*; 萩原雅人; 村田智城*; 廣瀬左京*; 木村剛*

no journal, ,

In recent years, ferroaxial order is discussed as a new class of ferroic states [1,2]. This order is a structural order characterized by a partial rotational distortion, which was initially introduced by R.D. Johnson et al. in 2011 [1]. It has been attracting increased interests because of its potential for unconventional physical phenomena and new functionalities such as transverse responses in which input external fields induce output conjugate physical quantities along the perpendicular direction [3]. However, only a few ferroaxial materials have been reported to date, (e.g., NiTiO $_{3}$ [4,5] and RbFe(MoO $_{4}$ ) $_{2}$ [5]). In this work, we sought new ferroaxial materials by formula-based screening using a regular expression search and the symmetry detection algorithm. As a result, we found that a glaserite- type compound, K $_{2}$ Zr(PO $_{4}$ ) $_{2}$ , is one of the promising candidates for ferroaxial materials. Furtheremore, our ab initio phonon calculations suggested that this compound undergoes a ferroaxial transition. Experimentally, by the structural analysis using neutron powder diffraction measurements, we demonstrated that K $_{2}$ Zr(PO $_{4}$ ) $_{2}$ shows a ferroaxial transition at about 700 K. The ferroaxial nature of K $_{2}$ Zr(PO $_{4}$ ) $_{2}$ was further confirmed by the observation of its domain structures using a linear electrogyration effect, that is, optical rotation in proportion to an applied electric field [6]. In this presentation, we will provide details of the database screening and the experiments. [1] R. D. Johnson et al., Phys. Rev. Lett. 107, 137205 (2011). [2] J. Hlinka et al., Phys. Rev. Lett. 116, 17 (2016). [3] S.-W. Cheong et al., npj Quantum Mater. 6, 58 (2021). [4] T. Hayashida et al., Nat. Commun. 11, 4582 (2020). [5] T. Hayashida et al., Phys. Rev. Mater. 5, 124409 (2021). [6] S. Yamagishi et al., Chem. Mater. 35, 747 (2023).