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論文

Magnetism of Al$$_{x}$$Fe$$_{2-x}$$GeO$$_{5}$$ with andalusite structure

柿本 和勇*; 高田 早紀*; 太田 寛人*; 原口 祐哉*; 萩原 雅人; 鳥居 周輝*; 神山 崇*; 三田村 裕幸*; 徳永 将史*; 畠山 温*; et al.

Journal of the Physical Society of Japan, 91(5), p.054704_1 - 054704_7, 2022/05

 被引用回数:1 パーセンタイル:29.72(Physics, Multidisciplinary)

The magnetism of Al$$_{x}$$Fe$$_{2-x}$$GeO$$_{5}$$ from $${x = 0.09}$$ to $${0.91}$$ with the andalusite structure was examined. Al$$_{x}$$Fe$$_{2-x}$$GeO$$_{5}$$ at low temperatures was found to show a weak ferromagnet-like behavior for $${x < 0.3}$$ and a spin glass behavior for $${x > 0.3}$$. The small spontaneous magnetization observed in the weak ferromagnet-like samples may be caused by the existence of Dzyaloshinsky-Moriya interaction and the difference in the magnitude of the magnetic moments of Fe$$^{3+}$$ in the octahedral and trigonal bipyramidal sites. The appearance of the spin glass behavior implies that the dilution of Fe ions by Al ions in Al$$_{x}$$Fe$$_{2-x}$$GeO$$_{5}$$ causes the competition between ferromagnetic and antiferromagnetic interactions. The $$x$$ dependence of the site occupancy of Fe ions suggests that Fe$$_{2}$$GeO$$_{5}$$ with the andalusite structure cannot be synthesized.

論文

Multipole polaron in the devil's staircase of CeSb

新井 陽介*; 黒田 健太*; 野本 拓也*; Tin, Z. H.*; 櫻木 俊輔*; Bareille, C.*; 明比 俊太朗*; 黒川 輝風*; 木下 雄斗*; Zhang, W.-L.*; et al.

Nature Materials, 21(4), p.410 - 415, 2022/04

 被引用回数:4 パーセンタイル:75.25(Chemistry, Physical)

Low-energy electronic structures of CeSb which shows multiple phase transitions known as devil's staircase were examined by combination of laser angle-resolved photoemission, Raman and neutron scattering spectroscopies. A new type of electron-boson coupling between the mobile electrons and quadrupole CEF-excitations of the 4f orbitals was found. The coupling is exceedingly strong and exhibits anomalous step-like enhancement during the devil's staircase transition, unveiling a new type of quasiparticle, named multipole polaron.

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

 被引用回数:0 パーセンタイル:10.97(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

Anisotropic physical properties of layered antiferromagnet U$$_2$$Pt$$_6$$Ga$$_{15}$$

松本 裕司*; 芳賀 芳範; 山本 悦嗣; 竹内 徹也*; 三宅 厚志*; 徳永 将史*

Journal of the Physical Society of Japan, 90(7), p.074707_1 - 074707_6, 2021/07

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

A uranium intermetallic compound U$$_2$$Pt$$_6$$Ga$$_{15}$$ was successfully synthesized. This compound crystallizes in the hexagonal Sc$$_{0.6}$$Fe$$_2$$Si$$_{4.9}$$-type structure. Antiferromagnetic transition with highly magnetic anisotropy was established by the physical property measurements.

論文

Critical slowing-down and field-dependent paramagnetic fluctuations in the skyrmion host EuPtSi; $$mu$$SR and NMR studies

比嘉 野乃花*; 伊藤 孝; 與儀 護*; 服部 泰佑; 酒井 宏典; 神戸 振作; Guguchia, Z.*; 髭本 亘; 中島 美帆*; 本間 佳哉*; et al.

Physical Review B, 104(4), p.045145_1 - 045145_7, 2021/07

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

We report the results of $$mu$$SR and $$^{29}$$Si NMR measurements carried out on the cubic chiral magnet EuPtSi. Our zero-field $$mu$$SR experiments revealed the development of critical slowing down of Eu spin fluctuations over a relatively wide critical region above $$T_N$$. We also found from $$^{29}$$Si NMR that the spin fluctuations are strongly suppressed by magnetic field in the paramagnetic state above 20K. These characteristic spin dynamics observed over a wide region of temperature and magnetic field suggest the presence of magnetic frustration in the spin system. Such frustration would underlie the mechanism stabilizing the short-period skyrmion lattice observed in this compound.

論文

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:1 パーセンタイル:17.22(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.

論文

Strong magnetic anisotropy and unusual magnetic field reinforced phase in URhSn with a quasi-kagome structure

清水 悠晴*; 三宅 厚志*; Maurya, A.*; 本多 史憲*; 仲村 愛*; 佐藤 芳樹*; Li, D.*; 本間 佳哉*; 横山 淳*; 徳永 陽; et al.

Physical Review B, 102(13), p.134411_1 - 134411_11, 2020/10

The physical properties of URhSn with quasi-kagome structure are studied using single-crystalline samples via electrical resistivity, magnetic susceptibility, heat capacity, thermal expansion, and high-field magnetization measurements. We found remarkable magnetic anisotropy in the ferromagnetic state below 16 K as well as in the ordered state between 16 K and 54 K.

論文

Intriguing behavior of UCo$$_{1-x}$$Rh$$_x$$Ge ferromagnets in magnetic field along the $$b$$ axis

Posp$'i$$v{s}$il, J.*; 芳賀 芳範; 三宅 厚志*; 神戸 振作; 徳永 陽; 徳永 将史*; 山本 悦嗣; Proschek, P.*; Voln$'y$, J.*; Sechovsk$'y$, V.*

Physical Review B, 102(2), p.024442_1 - 024442_13, 2020/07

 被引用回数:5 パーセンタイル:39.72(Materials Science, Multidisciplinary)

Alloying study of ferromagnetic superconductors URhGe and UCoGe is reported. The Curie temperature shows a maximum at Rh concentration $$x$$ = 0.4 in UCo$$_{1-x}$$Rh$$_x$$Ge. Magnetic characteristices in low- and high-$$x$$ regions are significantly different each other. The relationship between magnetism and superconductivity are discussed.

論文

Devil's staircase transition of the electronic structures in CeSb

黒田 健太*; 新井 陽介*; Rezaei, N.*; 國定 聡*; 櫻木 俊輔*; Alaei, M.*; 木下 雄斗*; Bareille, C.*; 野口 亮*; 中山 充大*; et al.

Nature Communications (Internet), 11, p.2888_1 - 2888_9, 2020/06

 被引用回数:14 パーセンタイル:74.84(Multidisciplinary Sciences)

Solids with competing interactions often undergo complex phase transitions. Among them, CeSb is the most famous material where a number of the distinct magnetic phases called devil's staircase appear. We observed the electronic structure evolution across the devil's staircase transitions using bulk-sensitive angle-resolved photoemission spectroscopy.

論文

Magnetic structures and quadratic magnetoelectric effect in LiNiPO$$_{4}$$ beyond 30 T

Fogh, E.*; 木原 工*; Toft-Petersen, R.*; Bartkowiak, M.*; 鳴海 康雄*; Prokhnenko, O.*; 三宅 厚志*; 徳永 将史*; 及川 健一; S${o}$rensen, M. K.*; et al.

Physical Review B, 101(2), p.024403_1 - 024403_12, 2020/01

 被引用回数:14 パーセンタイル:71.84(Materials Science, Multidisciplinary)

Neutron diffraction with static and pulsed magnetic fields is used to directly probe the magnetic structures in LiNiPO$$_{4}$$ up to 25 T and 42 T, respectively. By combining these results with magnetometry and electric polarization measurements under pulsed fields, the magnetic and magnetoelectric phases are investigated up to 56 T applied along the easy $$c$$ axis. In addition to the already known transitions at lower fields, three new ones are reported at 37.6, 39.4, and 54 T. Ordering vectors are identified with Q$$_{rm VI}$$ = (0, $$frac{1}{3}$$, 0) in the interval 37.6 - 39.4 T and Q$$_{rm VII}$$ = (0, 0, 0) in the interval 39.4 - 54 T. A quadratic magnetoelectric effect is discovered in the Q$$_{rm VII}$$= (0, 0, 0) phase and the field dependence of the induced electric polarization is described using a simple mean-field model. The observed magnetic structure and magnetoelectric tensor elements point to a change in the lattice symmetry in this phase. We speculate on the possible physical mechanism responsible for the magnetoelectric effect in LiNiPO$$_{4}$$.

論文

Magnetic fluctuation and first-order transition in trillium lattice of EuPtSi observed by $$^{151}$$Eu M$"o$ssbauer spectroscopy

本間 佳哉*; 垣花 将司*; 徳永 陽; 與儀 護*; 中島 美帆*; 仲村 愛*; 清水 悠晴*; Li, D.*; Maurya, A.*; 佐藤 芳樹*; et al.

Journal of the Physical Society of Japan, 88(9), p.094702_1 - 094702_8, 2019/08

We report the results of $$^{151}$$Eu M$"o$ssbauer spectroscopy on EuPtSi with a chiral structure belonging to the P2$$_{1}$$3 space group at zero magnetic field. The paramagnetic single absorption forms a magnetic splitting profile directly below 4.0 K and the spectrum at 3.9 K consists of the sum of the paramagnetic single absorption and the magnetic splitting absorption, which indicates a first-order transition at 4.0 K. The temperature dependence of the effective hyperfine fields at the Eu nucleus follows a power law indicates a full moment of Eu$$^{2+}$$ ions.

論文

Magnetic and electrical properties of the ternary compound U$$_2$$Ir$$_3$$Si$$_5$$ with one-dimensional uranium zigzag chains

Li, D. X.*; 本多 史憲*; 三宅 厚志*; 本間 佳哉*; 芳賀 芳範; 仲村 愛*; 清水 悠晴*; Maurya, A.*; 佐藤 芳樹*; 徳永 将史*; et al.

Physical Review B, 99(5), p.054408_1 - 054408_9, 2019/02

 被引用回数:3 パーセンタイル:28.12(Materials Science, Multidisciplinary)

Physical properties of the single-crystalline U$$_2$$Ir$$_3$$Si$$_5$$, a new ternary uranium compound with U$$_2$$Co$$_3$$Si$$_5$$-type orthorhombic structure, are investigated by means of magnetic susceptibility, specific heat and electrical resistivity. This compound undergoes an antiferromagnetic transition followed by a first-order phase transition at lower temperature. A possible mechanism of the first-order transition is the occurrence of a magnetic magnetic quadrupolar order, resulting from the quasi-one-dimensional uranium zigzag chain.

論文

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:15 パーセンタイル:62.22(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.

論文

Phonon density of states in Sr$$_{2}$$FeCoO$$_{6-delta}$$ and SrBaFeCoO$$_{6-delta}$$; Effects induced by magnetic order and transport coherence

Rykov, A. I.*; 野村 貴美*; 澤田 嗣郎*; 三井 隆也; 瀬戸 誠*; 為ヶ井 強*; 徳永 将史*

Physical Review B, 68(22), p.224401_1 - 224401_7, 2003/12

 被引用回数:8 パーセンタイル:42.99(Materials Science, Multidisciplinary)

遷移金属酸化物Sr$$_{2}$$FeCoO$$_{6-delta}$$, SrBaFeCoO$$_{6-delta}$$の低温での磁気相転移温度近傍における核共鳴非弾性散乱測定を行った。測定結果では、転移温度(Tc$$sim$$150K)に温度を下げるのにしたがい、非弾性散乱スペクトルの低エネルギー成分(14meV)に見られるピークが顕著に増加し、転移温度以下では分裂することが観測された。また、Tc以下では、20meV近傍のメインバンドエッジ部に顕著なソフトニングも観測された。本論文では、実験結果についての報告と、格子振動のソフトニングが、材料の磁気相転移発現時の超交換相互作用の変調効果によるものであることを示す。

口頭

(1-${it x}$)BiFeO$$_{3}$$-${it x}$BaTiO$$_{3}$$における微細構造と磁気特性・誘電特性の相関

尾崎 友厚*; 西原 禎文*; 細越 裕子*; 徳永 将史*; 野口 祐二*; 宮山 勝*; 吉井 賢資; 森 茂生*

no journal, , 

マルチフェロイック酸化物BiFeO$$_{3}$$の特性向上を狙い、標記の混晶系を作成し、その構造と物性について調べた。電子線回折による観察からは、x=0.35付近の試料においては、磁気ナノドメインと強誘電ナノドメインが共存することがわかった。55Tまでの磁場下誘電率測定からは、明瞭な電気磁気効果は見られなかったため、磁性と誘電性の相関は強くないことがわかった。また、磁化測定からは、非対称な磁化-外部磁場曲線が得られた。これはミクト磁性と呼ばれる磁性のクラスター的な応答によるものであり、混結領域では磁性ナノドメインが存在していることを示唆している。その他の試料のデータも合わせ、この系の構造と物性の詳細について議論する。

口頭

層状構造を持つウラン化合物U$$_2$$Pt$$_6$$Al$$_{15}$$の結晶構造と物性

芳賀 芳範; 常盤 欣文; 山本 悦嗣; 三宅 厚志*; 徳永 将史*

no journal, , 

U$$_2$$Pt$$_6$$Al$$_{15}$$の物性を報告する。10K及び25K付近に、磁気相転移を有する。両者は磁場中で異なる温度依存性を示し、その磁気特性は複雑である。同型の反強磁性体U$$_2$$Pt$$_6$$Ga$$_{15}$$と対比しつつ、それらの起源について議論する。

口頭

High field magnetization of UOX (X = S and Se)

Opletal, P.; 酒井 宏典; 芳賀 芳範; 三宅 厚志*; 徳永 将史*; 常盤 欣文; 山本 悦嗣; 神戸 振作; 徳永 陽

no journal, , 

UOX (X = S, Se, Te) crystallizes in tetragonal PbFCl-type structure (P4/nmm space group). Only polycrystalline samples are reported in literature. UOS, UOSe and UOTe were reported to be antiferromagnets with TN = 55, 100 and 160 K, respectively. We have presented recently that TN in UOS is much higher (TN = 82 K) and all compounds behave like semimetals. Magnetic structure of UOS and UOSe were reported to have moment along the c-axis with Q = (0,0,1/2). UOTe was theoretically predicted to have nontrivial topology. We will present the results of magnetization measurements in high magnetic fields for UOS and UOSe and their phase diagrams and their tricritical point. We will compare our results to current understanding of tricritical points in antiferromagnet and discuss possible scenarios.

口頭

Physical properties of semimetallic magnets UOX (X = S, Se, Te)

Opletal, P.; 酒井 宏典; 芳賀 芳範; 三宅 厚志*; 徳永 将史*; 常盤 欣文; 山本 悦嗣; 神戸 振作; 徳永 陽

no journal, , 

UOX (X = S, Se, Te) crystallizes in tetragonal PbFCl-type structure (P4/nmm space group). Only polycrystalline samples are reported in literature. UOS, UOSe and UOTe were reported to be antiferromagnets with T$$_{N}$$ = 55, 100 and 160 K, respectively. Magnetic structure of UOS and UOSe were reported to have moment along the c-axis with Q = (0,0,1/2). UOS and UOSe were both reported to exhibit semiconducting behavior on polycrystalline samples. UOTe was theoretically predicted to have nontrivial topology. We have prepared first single crystals of UOX (X = S, Se, Te) and shown they exhibit semimetallic conductivity and UOS exhibits increase of T$$_{N}$$ by almost 30 K in contrast to published literature. We will present the method of preparation of single crystals, results of magnetic, transport, thermal measurements, all effect and data obtained in high magnetic fields. We will discuss these results in connection to Weyl semimetals and results published in literature and anisotropy observed in electric resistivity.

口頭

Physical properties of semimetallic magnets UOX (X = S, Se, Te)

Opletal, P.; 酒井 宏典; 芳賀 芳範; 三宅 厚志*; 徳永 将史*; 常盤 欣文; 山本 悦嗣; 神戸 振作; 徳永 陽

no journal, , 

UOX (X = S, Se, Te) crystallizes in tetragonal PbFCl-type structure (P4/nmm space group). Only polycrystalline samples are reported in literature. UOS, UOSe and UOTe were reported to be antiferromagnets with T$$_{mathrm{N}}$$ = 55, 100 and 160 K, respectively. Magnetic structure of UOS and UOSe were reported to have moment along the c-axis with Q = (0,0,1/2). UOS and UOSe were both reported to exhibit semiconducting behavior on polycrystalline samples. UOTe was theoretically predicted to have nontrivial topology. We have prepared first single crystals of UOX (X = S, Se, Te) and shown they exhibit semimetallic conductivity and UOS exhibits increase of T$$_{mathrm{N}}$$ by almost 30 K in contrast to published literature. We will present the method of preparation of single crystals, results of magnetic, transport, thermal measurements, all effect and data obtained in high magnetic fields. We will discuss these results in connection to Weyl semimetals and results published in literature and anisotrpy observed in electric resistivity.

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