基本情報

所属

• 理学研究院　物理学部門　電子物性物理学分野

職名

• 教授

学位

• 博士(科学)（東京大学）

ホームページURL

https://kaken.nii.ac.jp/d/r/30566758.ja.html

J-Global ID

• 201501054594273816

研究キーワード

• 高温高圧合成法   水熱合成法   新物質探索   マルチフェロイクス   超伝導   フラストレーション   固体化学   固体物理学   物質科学   

研究分野

• 自然科学一般 / 磁性、超伝導、強相関系

担当教育組織

•  学士課程　理学部
•  修士課程　理学院
•  博士課程　理学院

職歴

• 2022年07月 - 現在 北海道大学 大学院理学研究院 教授
• 2018年04月 - 2022年06月 北海道大学 大学院理学研究院 准教授
• 2014年02月 - 2018年03月 北海道大学 大学院理学研究院 助教

所属学協会

• 日本物理学会   

研究活動情報

論文

• Frustrated Kagome Antiferromagnets under High Magnetic Fields

  Hiroyuki K. Yoshida

  Journal of the Physical Society of Japan 91 10 101003/1 - 101003/12 2022年10月15日 [査読有り][招待有り]
  
• μSR Study of Kapellasite-type Quantum Kagome Antiferromagnet CaCu₃(OH)₆Cl₂ ∙ 0.6H₂O

  Hiroyuki K. Yoshida, Hirotaka Okabe, Soshi Takeshita, Hubertus Luetkens, Akihiro Koda, Ryosuke Kadono

  Journal of the Physical Society of Japan 91 1 013701/1 - 013701/5 2022年01月15日 [査読有り][通常論文]
  
• Magnetic properties of the Shastry-Sutherland lattice material BaNd2ZnO5

  Yuto Ishii, G. Sala, M. B. Stone, V. O. Garlea, S. Calder, Jie Chen, Hiroyuki K. Yoshida, Shuhei Fukuoka, Jiaqiang Yan, Clarina dela Cruz, Mao-Hua Du, David S. Parker, Hao Zhang, Cristian D. Batista, Kazunari Yamaura, A. D. Christianson

  Physical Review Materials 5 6 064418-1 - 064418-11 2021年06月28日 [査読有り]
  
• Observation of domain wall bimerons in chiral magnets

  Tomoki Nagase, Yeong-Gi So, Hayata Yasui, Takafumi Ishida, Hiroyuki K. Yoshida, Yukio Tanaka, Koh Saitoh, Nobuyuki Ikarashi, Yuki Kawaguchi, Makoto Kuwahara, Masahiro Nagao

  Nature Communications 12 1 3490 - 3490 2021年06月 [査読有り]
   

  Topological defects embedded in or combined with domain walls have been proposed in various systems, some of which are referred to as domain wall skyrmions or domain wall bimerons. However, the experimental observation of such topological defects remains an ongoing challenge. Here, using Lorentz transmission electron microscopy, we report the experimental discovery of domain wall bimerons in chiral magnet Co-Zn-Mn(110) thin films. By applying a magnetic field, multidomain structures develop, and simultaneously, chained or isolated bimerons arise as the localized state between the domains with the opposite in-plane components of net magnetization. The multidomain formation is attributed to magnetic anisotropy and dipolar interaction, and domain wall bimerons are stabilized by the Dzyaloshinskii-Moriya interaction. In addition, micromagnetic simulations show that domain wall bimerons appear for a wide range of conditions in chiral magnets with cubic magnetic anisotropy. Our results promote further study in various fields of physics.
• Magnetic Properties of S = 1/2 Distorted Kagome Antiferromagnet CdCu3(OH)6Cl2 with Low-Symmetry Orbital Arrangement

  Hiroyuki K. Yoshida, Naoya Noguchi, Yuto Ishii, Migaku Oda, Jie Chen, Kazunari Yamaura, Satoshi Yamashita, Yasuhiro Nakazawa, Takanori Kida, Yasuo Narumi, Masayuki Hagiwara

  Journal of the Physical Society of Japan 90 4 044714/1 - 044714/6 2021年04月15日 [査読有り]
   

  The magnetic properties of the S = 1/2 distorted kagome antiferromagnet CdCu3(OH)(6)Cl-2 have been studied by magnetic susceptibility, heat capacity, and high-field magnetization measurements. The magnetic susceptibility and heat capacity measurements indicated the absence of a magnetic long-range order down to 0.7 K, and the magnetization exhibited spin polarization of one-third of the total spins in a relatively weak magnetic field. The observed magnetic behavior of CdCu3(OH)(6)Cl-2 was analyzed qualitatively by using a kagome model with three different exchange interactions that connects the regular kagome antiferromagnet and the isolated one-dimensional chain with inter-chain free spins. The orbital arrangement of Cu2+ ions induced a difference in the exchange interactions in the kagome lattice, and the interplay between the orbital and spin states gave rise to unique magnetic properties in the kagome antiferromagnet.
• Field-induced successive phase transitions in the J1−J2 buckled honeycomb antiferromagnet Cs3Fe2Cl9

  Y. Ishii, Y. Narumi, Y. Matsushita, M. Oda, T. Kida, M. Hagiwara, H. K. Yoshida

  Physical Review B 103 10 104433/1 - 104433/11 2021年03月25日 [査読有り]
  
• Emergence of Frustrated Short-Range Order above Long-Range Order in the S = 1/2 Kagome Antiferromagnet CaCu3(OD)6Cl2∙0.6D2O

  Yoshihiko Ihara, Kazuki Matsui, Yoshimitsu Kohama, Sven Luther, Daryna Opherden, Jochen Wosnitza, Hannes Kühne, Hiroyuki K. Yoshida

  Journal of the Physical Society of Japan 90 2 023703/1 - 023703/5 2021年02月15日 [査読有り]
   

  We report on the low-energy dynamics in the kagome antiferromagnet CaCu3(OD)6Cl2·0.6D2O (Ca-kapellasite) as studied by use of 2D-NMR measurements. Previous 35Cl-NMR measurements revealed that the nuclear spin-lattice relaxation rate (1=T1) shows two peaks at temperatures, T∗ = 7.2K and Ts ≃ 25 K. While the low-temperature peak at T∗ is ascribed to the critical fluctuations near the long-range magnetic ordering, the origin of the high-temperature peak has not been fully understood. From the 1=T1 measurements on the D sites at the OD groups (DOD), we find no peak at Ts, evidencing that the high-temperature peak is not related to the molecular dynamics of the OD groups. We discuss the possibility of a frustration-induced short-range ordered state below Ts before the long-range order is stabilized by the Dzyaloshinskii-Moriya interaction. We also observed static internal fields at the DOD site in the long-range ordered state below T∗, and confirm the previously proposed negative-chirality q = 0 magnetic structure.
• Magnetic excitations affected by spin-lattice coupling in the S=32 triangular lattice antiferromagnet Ag2CrO2

  Masaaki Matsuda, Sachith E. Dissanayake, Hiroyuki K. Yoshida, Masaaki Isobe, Matthew B. Stone

  Physical Review B 102 21 214411/1 - 214411/6 2020年12月09日 [査読有り]
  
• Butterfly-shaped magnetoresistance in triangular-lattice antiferromagnet Ag2CrO2

  Hiroki Taniguchi, Mori Watanabe, Masashi Tokuda, Shota Suzuki, Eria Imada, Takashi Ibe, Tomonori Arakawa, Hiroyuki Yoshida, Hiroaki Ishizuka, Kensuke Kobayashi, Yasuhiro Niimi

  Scientific Reports 10 1 2525  2020年12月 [査読有り][通常論文]
  
• Coexistence of checkerboard and quasiparticle interference modulations in Bi2Sr2CaCu2O8+x studied by scanning tunneling microscopy/spectroscopy

  Shusei Mizuta, Migaku Oda, Naoki Momono, Hiroyuki K. Yoshida, Masayuki Ido

  Physical Review B 102 18 184513/1 - 184513/8 2020年11月23日 [査読有り]
   

  We performed scanning tunneling microscopy/spectroscopy measurements in the superconducting state of underdoped Bi(2)Sr(2)CaCu(2)O(8+x )and demonstrated that the checkerboard (CB) and Bogoliubov quasiparticle interference (QPI) modulations, which are considered to be characteristic features for the low-energy states around the antinodal and nodal regions of the Fermi surface, respectively, coexist in identical regions of the Cu-O plane. In the present work, these electronic superstructures are successfully separated from each other, and the local amplitude and phase are evaluated for the CB modulation and the q(1) component of QPI, which are characterized by similar wave vectors. The q(1)-QPI component tends to be in-phase and antiphase with the CB modulation for positive and negative bias voltages, respectively. The significant spatial phase relationship is confirmed in regions where the local amplitude of CB modulation is comparatively large. This finding implies an interplay between the QPI and CB modulations.
• Partially disordered state with short-range spin correlation in S=5/2 classical triangular antiferromagnet Ag2FeO2

  H. K. Yoshida, M. Matsuda, M. B. Stone, C. R. dela Cruz, T. Furubayashi, M. Onoda, E. Takayama-Muromachi, M. Isobe

  Physical Review Research 2 4 2020年11月10日
• High-pressure synthesis, crystal structure, and magnetic properties of the Shastry-Sutherland-lattice oxides BaLn2ZnO5 (Ln = Pr, Sm, Eu)

  Yuto Ishii, Jie Chen, Hiroyuki K. Yoshida, Migaku Oda, Andrew D. Christianson, Kazunari Yamaura

  Journal of Solid State Chemistry 289 121489 - 121489 2020年09月
• Static and dynamic spin properties in the quantum triangular lattice antiferromagnet Ag2CoO2

  H. K. Yoshida, S. E. Dissanayake, A. D. Christianson, C. R. dela Cruz, Y.-Q. Cheng, S. Okamoto, K. Yamaura, M. Isobe, M. Matsuda

  Physical Review B 102 2 2020年07月29日
• q=0 long-range magnetic order in centennialite CaCu3(OD)6Cl2·0.6D2O: A spin-12 perfect kagome antiferromagnet with J1−J2−Jd

  K. Iida, H. K. Yoshida, A. Nakao, H. O. Jeschke, Y. Iqbal, K. Nakajima, S. Ohira-Kawamura, K. Munakata, Y. Inamura, N. Murai, M. Ishikado, R. Kumai, T. Okada, M. Oda, K. Kakurai, M. Matsuda

  Physical Review B 101 22 2020年06月22日 

  Crystal and magnetic structures of the mineral centennialite CaCu3(OH)(6)Cl-2 center dot 0.6H(2)O are investigated by means of synchrotron x-ray diffraction and neutron diffraction measurements complemented by density functional theory (DFT) and pseudofermion functional renormalization group (PFFRG) calculations. CaCu3(OH)(6)Cl-2 center dot 0.6H(2)O crystallizes in the P (3) over bar m1 space group and Cu2+ ions form a geometrically perfect kagome network with antiferromagnetic J(1). No intersite disorder between Cu2+ and Ca2+ ions is detected. CaCu3(OH)(6)Cl-2 center dot 0.6H(2)O enters a magnetic long-range ordered state below T-N = 7.2 K, and the q = 0 magnetic structure with negative vector spin chirality is obtained. The ordered moment at 0.3 K is suppressed to 0.58(2)mu(B). Our DFT calculations indicate the presence of antiferromagnetic J(2) and ferromagnetic J(d) superexchange couplings of a strength which places the system at the crossroads of three magnetic orders (at the classical level) and a spin-1/2 PFFRG analysis shows a dominance of q = 0 type magnetic correlations, consistent with and indicating proximity to the observed q = 0 spin structure. The results suggest that this material is located close to a quantum critical point and is a good realization of a J(1)-J(2)-J(d) kagome antiferromagnet.
• Anisotropic magnetic excitations from single-chirality antiferromagnetic state in Ca-kapellasite

  Y. Ihara, H. Yoshida, K. Arashima, M. Hirata, T. Sasaki

  Physical Review Research 2 2 2020年06月02日
• Thermal-transport studies of kagomé antiferromagnets

  M. Yamashita, M. Akazawa, M. Shimozawa, T. Shibauchi, Y. Matsuda, H. Ishikawa, T. Yajima, Z. Hiroi, M. Oda, H. Yoshida, H.-Y. Lee, J. H. Han, N. Kawashima

  Journal of Physics: Condensed Matter 32 7 074001  2020年 [査読有り][通常論文]
   

  Searching for the ground state of a kagom Heisenberg antiferromagnet (KHA) has been one of the central issues of condensed-matter physics, because the KHA is expected to host spin-liquid phases with exotic elementary excitations. Here, we show our longitudinal () and transverse () thermal conductivities measurements of the two kagom materials, volborthite and Ca kapellasite. Although magnetic orders appear at temperatures much lower than the antiferromagnetic energy scale in both materials, the nature of spin liquids can be captured above the transition temperatures. The temperature and field dependence of is analyzed by spin and phonon contributions, and large sample variations of the spin contribution are found in volborthite. Clear changes in are observed at the multiple magnetic transitions in volborthite, showing different magnetic thermal conduction in different magnetic structures. These magnetic contributions are not clearly observed in low- crystals of volborthite, and are almost absent in Ca kapellasite, showing the high sensitivity of the magnetic excitation in to the defects in crystals. On the other hand, a clear thermal Hall signal has been observed in the lowest- crystal of volborthite and in Ca kapellasite. Remarkably, both the temperature dependence and the magnitude of of volborthite are found to be very similar to those of Ca kapellasite, despite of about an order of magnitude difference in We find that of both compounds is well reproduced, both qualitatively and quantitatively, by spin excitations described by the Schwinger-boson mean-field theory applied to KHA with the Dzyaloshinskii?Moriya interaction. This excellent agreement demonstrates not only that the thermal Hall effect in these kagom antiferromagnets is caused by spins in the spin liquid phase, but also that the elementary excitations of this spin liquid phase are well described by the bosonic spin excitations.
• Smectic Liquid-Crystalline Structure of Skyrmions in Chiral Magnet Co8.5Zn7.5Mn4 (110) Thin Film

  T. Nagase, M. Komatsu, Y. G. So, T. Ishida, H. Yoshida, Y. Kawaguchi, Y. Tanaka, K. Saitoh, N. Ikarashi, M. Kuwahara, M. Nagao

  Physical Review Letters 123 13 137203  2019年 [査読有り][通常論文]
   

  The organizing of magnetic skyrmions shows several forms similar to atomic arrays of solid states. Using Lorentz transmission electron microscopy, we report the first direct observation of a stable liquid-crystalline structure of skyrmions in chiral magnet Co8.5Zn7.5Mn4(110) thin film, caused by magnetic anisotropy and chiral surface twist. Elongated skyrmions are oriented and periodically arranged only in the -110 directions, whereas they exhibit short-range order along the 001 directions, indicating a smectic skyrmion state. In addition, skyrmions possess anisotropic interaction with an opposite sign depending on the crystal orientation, in contrast to existing isotropic interaction.
• Orbital Transitions and Frustrated Magnetism in the Kagome-Type Copper Mineral Volborthite

  Z. Hiroi, H. Ishikawa, H. Yoshida, J. Yamaura, Y. Okamoto

  Inorganic Chemistry 58 18 11949 - 11960 2019年 [査読有り][通常論文]
   

  Volborthite Cu3V2O7(OH)2·2H2O is a copper mineral that materializes a two-dimensional quantum magnet comprising a kagome net of spin-1/2 Cu2+ ions. We prepared single crystals of volborthite using hydrothermal conditions and investigated their crystal structures and magnetic properties. Unusual orbital "switching" and "flipping" transitions were observed: in the former type of transition (switching), the Cu 3d orbital occupied by an unpaired electron changes between the d(3z2-r2) and d(x2-y2) types, and in the latter type of transition (flipping), the d(x2-y2)-type orbitals change their directions. Their origin is ascribed to variations in the orientation of water molecules in the gap between the kagome layers and the accompanying changes of hydrogen bonding. These orbital transitions dramatically modify the magnetic interactions between Cu2+ spins, from the anisotropic kagome type to the formation of spin trimers over the kagome net. The effective spin 1/2 generated on the trimers exhibits a frustrated magnetism, resulting in a rich phase diagram in the magnetic fields. Volborthite is a unique compound showing an exceptional interplay between the orbital and spin degrees of freedom.
• Coexisting spin resonance and long-range magnetic order of Eu in EuRbFe4As4

  K. Iida, Y. Nagai, S. Ishida, M. Ishikado, N. Murai, A. D. Christianson, H. Yoshida, Y. Inamura, H. Nakamura, A. Nakao, K. Munakata, D. Kagerbauer, M. Eisterer, K. Kawashima, Y. Yoshida, H. Eisaki, A. Iyo

  Physical Review B 100 1 014506  2019年 [査読有り][通常論文]
   

  © 2019 American Physical Society. Magnetic excitations and magnetic structure of EuRbFe4As4 were investigated by inelastic neutron scattering (INS), neutron diffraction, and random phase approximation (RPA) calculations. Below the superconducting transition temperature Tc=36.5 K, the INS spectra exhibit the neutron spin resonances at Qres=1.27(2) and 1.79(3)Å-1. They correspond to the Q=(0.5,0.5,1) and (0.5,0.5,3) nesting wave vectors, showing three-dimensional nature of the band structure. The characteristic energy of the neutron spin resonance is Eres=17.7(3) meV corresponding to 5.7(1)kBTc. Observation of the neutron spin resonance mode and our RPA calculations in conjunction with the recent optical conductivity measurements are indicative of the s± superconducting pairing symmetry in EuRbFe4As4. In addition to the neutron spin resonance mode, upon decreasing temperature below the magnetic transition temperature TN=15 K, the spin wave excitation originating in the long-range magnetic order of the Eu sublattice was observed in the low-energy inelastic channel. Single-crystal neutron diffraction measurements demonstrate that the magnetic propagation vector of the Eu sublattice is k=(0,0,0.25), representing the three-dimensional antiferromagnetic order. Linear spin wave calculations assuming the obtained magnetic structure with the intra- and interplane nearest neighbor exchange couplings of J1/kB=-1.31 K and Jc/kB=0.08 K can reproduce quantitatively the observed spin wave excitation. Our results show that superconductivity and long-range magnetic order of Eu coexist in EuRbFe4As4, whereas the coupling between them is rather weak.
• Fabrication of thin films of two-dimensional triangular antiferromagnet Ag2CrO2 and their transport properties

  Hiroki Taniguchi, Shota Suzuki, Tomonori Arakawa, Hiroyuki Yoshida, Yasuhiro Niimi, Kensuke Kobayashi

  AIP Advances 8 2 025010 - 025010 2018年02月 [査読有り][通常論文]
  
• 三角格子反強磁性体Li₂AMo₃O₈ (A = In, Sc)のμSR

  岡部 博孝, 幸田 章宏, 平石 雅俊, 竹下 聡史, 小嶋 健児, 門野 良典, 飯田 一樹, 梶本 亮一, 吉田 紘行, 石井 裕人, 村井 直樹, 石角 元志, 稲村 泰弘, 中島 健次

  日本物理学会講演概要集 73 516 - 516 一般社団法人 日本物理学会 2018年
• Quantum magnetisms in uniform triangular lattices Li2AMo3O8 (A = In, Sc)

  K. Iida, H. Yoshida, H. Okabe, N. Katayama, Y. Ishii, A. Koda, Y. Inamura, N. Murai, M. Ishikado, R. Kadono, R. Kajimoto

  Scientific Reports 2018年 [査読有り][通常論文]
  
• Spin Thermal Hall Conductivity of a Kagome Antoferromagnet

  H. Doki, M. Akazawa, H.-Y. Lee, J.H Han, K. Sugii, M. Shimozawa, N. Kawashima, M. Oda, H. Yoshida, M. Yamashita

  Physical Review Letters 121 9 097203  2018年 [査読有り][通常論文]
   

  A clear thermal Hall signal (kappa(xy)) was observed in the spin-liquid phase of the S = 1/2 kagome antiferromagnet Ca kapellasite [CaCu3(OH)(6)Cl-2 center dot 0.6H(2)O]. We found that kappa(xy) is well reproduced, both qualitatively and quantitatively, using the Schwinger-boson mean-field theory with the Dzyaloshinskii-Moriya interaction of D/J similar to 0.1. In particular,kappa(xy) values of Ca kapellasite and those of another kagome antiferromagnet, volborthite, converge to one single curve in simulations modeled using Schwinger bosons, indicating a common temperature dependence of kappa(xy) for the spins of a kagome antiferromagnet.
• Spin dynamics in the high-field phases of volborthite

  M. Yoshida, K. Nawa, H. Ishikawa, M. Takigawa, M. Jeong, S. Kramer, M. Horvatic, C. Berthier, K. Matsui, T. Goto, S. Kimura, T. Sasaki, J. Yamaura, H. Yoshida, Y. Okamoto, Z. Hiroi

  PHYSICAL REVIEW B 96 18 180413(R)  2017年11月 [査読有り][通常論文]
   

  We report single-crystal V-51 NMR studies on volborthite Cu3V2O7(OH)(2) center dot 2H(2)O, which is regarded as a quasi-two-dimensional frustrated magnet with competing ferromagnetic and antiferromagnetic interactions. In the 1/3 magnetization plateau above 28 T, the nuclear spin-lattice relaxation rate 1/T-1 indicates an excitation gap with a large effective g factor in the range of 4.6-5.9, pointing to magnon bound states. Below 26 T where the gap has closed, the NMR spectra indicate small internal fields with a Gaussian-like distribution, whereas 1/T-1 shows a power-law-like temperature dependence in the paramagnetic state, which resembles a slowing down of spin fluctuations associated with magnetic order. We discuss the possibility of an exotic spin state caused by the condensation of magnon bound states below the magnetization plateau.
• Gapless magnetic excitations in the kagome antiferromagnet Ca-kapellasite probed by Cl-35 NMR spectroscopy

  Y. Ihara, T. Sasaki, N. Noguchi, Y. Ishii, M. Oda, H. Yoshida

  PHYSICAL REVIEW B 96 18 180409(R)  2017年11月 [査読有り][通常論文]
   

  The low-energy magnetic excitations of the spin-1/2 kagome antiferromagnet CaCu3(OH)(6)Cl-2 center dot 0.6H(2)O (Ca-kapellasite) have been investigated by a Cl-35 NMR experiment in fields up to 18.9 T. Recently, Ca-kapellasite was found to be one of the most promising candidates to explore the intrinsic magnetic properties in kagome antiferromagnets, because magnetic defects, which deteriorate the intrinsic magnetic properties, are minimized by choosing Ca ions with a large ionic radius as the counterions. From our nuclear spin-lattice relaxation rate 1/T-1 measurement, we found a power-law temperature dependence below the magnetic ordering temperature T-M = 7.2 K, which leads us to suggest that gapless magnetic excitations survive even in the ordered state. This power-law behavior is suppressed in high magnetic fields. We discuss a possible magnetic state that can generate gapless excitations at low fields.
• Spin Resonance in the New-Structure-Type Iron-Based Superconductor CaKFe4As4

  Kazuki Iida, Motoyuki Ishikado, Yuki Nagai, Hiroyuki Yoshida, Andrew D. Christianson, Naoki Murai, Kenji Kawashima, Yoshiyuki Yoshida, Hiroshi Eisaki, Akira Iyo

  JOURNAL OF THE PHYSICAL SOCIETY OF JAPAN 86 9 093703  2017年09月 [査読有り][通常論文]
   

  The dynamical spin susceptibility in the new-structure-type iron-based superconductor CaKFe4As4 was investigated by using a combination of inelastic neutron scattering (INS) measurements and random phase approximation (RPA) calculations. Powder INS measurements show that the spin resonance at Q(res) = 1.17(1) angstrom(-1), corresponding to the (pi,pi) nesting wave vector in tetragonal notation, evolves below T-c. The characteristic energy of the spin resonance E-res = 12.5meV is smaller than twice the size of the superconducting gap (2 Delta). The broad energy feature of the dynamical susceptibility of the spin resonance can be explained by the RPA calculations, in which the different superconducting gaps on different Fermi surfaces are taken into account. Our INS and PRA studies demonstrate that the superconducting pairing nature in CaKFe4As4 is the s(+/-) symmetry.
• Superconductivity in noncentrosymmetric Ag2Pd3S

  H. Yoshida, H. Okabe, Y. Matsushita, M. Isobe, E. Takayama-Muromachi

  PHYSICAL REVIEW B 95 18 184514  2017年05月 [査読有り][通常論文]
   

  We have successfully synthesized the single crystal of Ag2Pd3S, which exhibits superconductivity with the transition temperature of T-c = 2.25 K. Ag2Pd3S crystallizes in the space group P4(1)32 with the filled beta-Mn structure, which has no inversion symmetry. The value of the Ginzburg-Landau parameter.GL indicates that Ag2Pd3S is a type-II superconductor. Delta C(T-c)gamma T-n(c) = 1.50 and 2 Delta/k(B)T(c) = 3.48 from the heat-capacity analyses indicate that Ag2Pd3S is a weak-coupling Bardeen-Cooper-Schrieffer (BCS) superconductor with an isotropic superconducting gap. On the other hand, the violation of the Werthamer-Helfand-Hohenberg curve in the H-T phase diagram implies Ag2Pd3S is not a typical BCS superconductor.
• Unusual Magnetic State with Dual Magnetic Excitations in the Single Crystal of S = 1/2 Kagome Lattice Antiferromagnet CaCu3(OH)6Cl2・0.6H2O

  H. Yoshida, N. Noguchi, Y. Matsushita, Y. Ishii, Y. Ihara, M. Oda, H. Okabe, S. Yamashita, Y. Nakazawa, A. Takata, T. Kida, Y. Narumi, M. Hagiwara

  Journal of the Physical Society of Japan 86 3 033704  2017年03月 [査読有り][通常論文]
   

  We have succeeded in preparing single crystals of CaCu3(OH)(6)Cl-2 center dot 0.6H(2)O, a candidate for the S = 1/2 Kagome lattice antiferromagnet. Magnetic properties of the compound are dominated by the nearest neighbor antiferromagnetic interaction J(1), and the next nearest neighbor ferromagnetic J(2) and an antiferromagnetic J(d) across a hexagon, which is different from related compounds Kapellasite and Haydeeite with ferromagnetic J(1). Magnetic susceptibility exhibits a sudden increase below 13K and a cusp anomaly at T* = 7.2K in the ab-plane, whereas only a moderate enhancement is observed below T* along the c-axis. A tiny peak detected in heat capacity at T* indicates the occurrence of a magnetic phase transition. The low temperature magnetic heat capacity was reproduced by assuming a two-dimensional spin-wave component and a temperature-linear term. The spin-wave contribution suggests a magnon excitation in a short-range ordered region, whereas the relatively large T-linear term 5.9 mJ/(Cu-mol center dot K-2) at H = 0T of this insulating compound suggests the existence of an unusual quasi-particle excitation below T*. They apparently reveal the unconventionality of the ground state of this S = 1/2 Kagome lattice antiferromagnet.
• Structural study of quasi-one-dimensional vanadium pyroxene LiVSi2O6 single crystals

  Yuto Ishii, Yoshitaka Matsushita, Migaku Oda, Hiroyuki Yoshida

  JOURNAL OF SOLID STATE CHEMISTRY 246 125 - 129 2017年02月 [査読有り][通常論文]
   

  Single crystals of quasi-one-dimensional vanadium pyroxene LiVSi2O6 were synthesized and the crystal structures at 293 K and 113 K were studied using X-ray diffraction experiments. We found a structural phase transition from the room-temperature crystal structure with space group C2/c to a low-temperature structure with space group P2(I)/c, resulting from a rotational displacement of SiO4 tetrahedra. The temperature dependence of magnetic susceptibility shows a broad maximum around 116 K, suggesting an opening of the Haldane gap expected for one-dimensional antiferromagnets with S=1. However, an antiferromagnetic long-range order was developed below 24 K, probably caused by a weak inter-chain magnetic coupling in the compound.
• STM/STS study on electronic superstructures in the superconducting state of high-Tc cuprate Bi2Sr2CaCu2O8+d

  S. Mizuta, T. Kurosawa, K Takeyama, N. Momono, Y. Ishii, H. Yoshida, M. Oda, M. Ido

  Journal of Physics: Condensed Matter 2017年 [査読有り][通常論文]
  
• Out-of-Plane Disorder Effects on the Energy Gaps and Electronic Charge Order in Bi2Sr1.7R0.3CuO6+δ (R = La and Eu)

  T. Kurosawa, K. Takeyama, S. Baar, Y. Shibata, M. Kataoka, S. Mizuta, H. Yoshida, N. Momono, M. Oda, M. Ido

  Journal of the Physical Society of Japan 85 4 044706  2016年04月 [査読有り][通常論文]
   

  We performed STM/STS experiments at 8K in Bi2Sr1.7R0.3CuO6+delta (R-Bi2201) systems that had optimal (OP) holedoping levels (similar to 0.17) but different T-c values, 35K for R = La and 20K for R = Eu, and examined out-of-plane disorder effects on the superconducting (SC) gap (SCG) and the pseudogap (PG) which is associated with the so-called "checkerboard charge order" (CCO). As out-of-plane disorders are strengthened by replacing La with Eu in OP R-Bi2201, the antinodal PG size Delta(PG) increases from similar to 30 to similar to 60 meV, the nodal SCG size Delta(SC) seems to decrease from similar to 7 to similar to 4 meV, and the pairing gap amplitude Delta(0) or d-wave gap size at the antinodes is almost unchanged (Delta(0) similar to 15 meV). These gap sizes for OP doping in Eu-Bi2201 are comparable to those for an underdoping level of similar to 0.1 in La-Bi2201. Although out-of-plane disorders strongly affect the electronic system of the Cu-O plane, they have no effect on the period of the CCO, which is five times the lattice constant (5a) along the Cu-O bond directions for OP doping and 4a for p similar to 0.1. We suggest that the concentration of holes doped into the Cu-O plane may be an essential factor for determining the period of the CCO.
• 19aPS-75 S=5/2三角格子ダイマーCs_3Fe_2Cl_9の磁性

  石井 裕人, 野口 直彌, 吉田 紘行, 小田 研

  日本物理学会講演概要集 71 1081 - 1081 一般社団法人日本物理学会 2016年
• 19aPS-43 擬一次元量子スピン系CaCu_2(OH)_3Cl_3のスピン一重項状態

  野口 直彌, 石井 裕人, 吉田 紘行, 松下 能孝, 小田 研

  日本物理学会講演概要集 71 1050 - 1050 一般社団法人日本物理学会 2016年
• 22aBC-2 μSRで見たβ'-LiCoPO_4の長時間磁気相変態現象

  岡部 博孝, 平石 雅俊, 山内 一宏, 竹下 聡史, 幸田 章宏, 小嶋 健児, 門野 良典, 吉田 紘行, 宮川 仁, 松下 能孝

  日本物理学会講演概要集 71 1289 - 1289 一般社団法人日本物理学会 2016年
• STM/STSから見たBi2212の電荷秩序とエネルギーギャップ

  水田 崇聖, 岸 文香, 米川 雄太, 黒沢 徹, 桃野 直樹, 竹山 幸作, 吉田 紘行, 小田 研, 伊土 政幸

  日本物理学会講演概要集 71 1993 - 1993 一般社団法人 日本物理学会 2016年 

  銅酸化物高温超伝導体Bi2212のアンダードープ試料においてSTM/STS実験を行い、この系で問題となっている電荷秩序が観測されるエネルギー領域（電子的な準粒子状態に対応する正の適当なエネルギー領域でのみ観測されるか？）について調べた。また、このエネルギー領域と超伝導ギャップや擬ギャップとの関係についても調べた。講演では、これらの結果について報告する。

• Experimental observation of multiple-Q states for the magnetic skyrmion lattice and skyrmion excitations under a zero magnetic field

  Masahiro Nagao, Yeong-Gi So, Hiroyuki Yoshida, Kazunari Yamaura, Takuro Nagai, Toru Hara, Atsushi Yamazaki, Koji Kimoto

  PHYSICAL REVIEW B 92 14 140415(R)  2015年10月 [査読有り][通常論文]
   

  Model calculations indicate that the magnetic skyrmion lattice (SkL) is represented by a superposition of three spin helices at an angle of 120 degrees to each other, the so-called triple-Q state. Using Lorentz transmission electron microscopy, we investigated the relationship between the SkL and the helix in FeGe thin films. After the magnetic field is removed, the ordered skyrmions are trapped inside helimagnetic domain walls (HDWs) where the different helical Q vectors are encountered. In situ observation revealed an unexpected topological excitation under such a zero-field state: skyrmions are spontaneously formed at HDWs.
• STM/STS studies for interplane disorder effects on the electronic states of the Cu-O plane in Bi2201

  T. Kurosawa, G. Hatta, H. Miyazaki, J. Yamaji, K. Yoshikawa, Y. Nakagawa, Y. Shibata, H. Yoshida, M. Oda, M. Ido, K. Takeyama, N. Momono

  INTERNATIONAL JOURNAL OF MODERN PHYSICS B 29 25-26 1542009  2015年10月 [査読有り][通常論文]
   

  STM/STS experiments have been performed in Bi2Sr1.7R0.3CuO6+delta (R-Bi2201) systems with R = La and Eu, which are of a nearly optimal doping level p(o) but have different T-c values, 35 K and 20 K, respectively, to examine interplane disorder effects on the superconducting (SC) gap and the pseudogap (PG) that is accompanied by a checkerboard-type charge order (CCO). We report that as interplane disorders are strengthened by replacing La with Eu in optimal Bi2201, the antinodal PG size Delta* increases from similar to 30 meV to similar to 60 meV, which is comparable to the value for an under-doping level p/p(o) similar to 0.5 in La-Bi2201. On the other hand, the period of CCO in optimal Eu-Bi2201 is the same as in optimal La-Bi2201, about five times lattice constant similar to 5a along the Cu-O bond directions; it remains unchanged even if the PG develops markedly to the same degree as for p/p(o) similar to 0.5 in La-Bi2201, whose period is similar to 4a.
• Real space observation of skyrmion polycrystallization and its domain boundary behavior in FeGe1-xSix

  Masahiro Nagao, Yeong-Gi So, Hiroyuki Yoshida, Takuro Nagai, Keiichi Edagawa, Kaichi Saito, Toru Hara, Atsushi Yamazaki, Koji Kimoto

  APPLIED PHYSICS EXPRESS 8 3 033001/1 - 033001/4 2015年03月 [査読有り][通常論文]
   

  In magnetic skyrmion crystals (SkXs), the quality of skyrmion ordering affects the motion under electric current and temperature gradient. However, the crystalline nature itself remains an open issue. We report the observation of skyrmion polycrystallization in FeGe1-xSix as a function of x by Lorentz transmission electron microscopy. With increasing x, the SkX changes from single crystalline to polycrystalline, concomitantly with the formation of the interfaces referred to as domain boundaries. In situ observations have revealed that the domain boundary formation competes the tendency to accommodate the differences between orientations of the SkX. (C) 2015 The Japan Society of Applied Physics
• 22aAH-7 三角格子反強磁性体β'-LiCoPO_4の合成と物性

  吉田 紘行, 宮川 仁, 松下 能孝, 岡部 博孝

  日本物理学会講演概要集 70 1156 - 1156 一般社団法人日本物理学会 2015年
• 18aCG-5 新奇スピン1/2 カゴメ格子反強磁性体CaCu_3(OH)_6Cl_2・0.67H_2O の磁性

  野口 直彌, 石井 裕人, 片岡 萌子, 吉田 紘行, 松下 能孝, 小田 研

  日本物理学会講演概要集 70 911 - 911 一般社団法人日本物理学会 2015年
• 18aCG-7 S = 3/2 カゴメ格子反強磁性体 Li_2Cr_3SbO_8 の磁性

  石井 裕人, 野口 直彌, 片岡 萌子, 吉田 紘行, 山浦 一成, 宮川 仁, 小田 研

  日本物理学会講演概要集 70 913 - 913 一般社団法人日本物理学会 2015年
• 17aCM-4 三角格子反強磁性体β'-LiCoPO_4 の磁気構造解析

  吉田 紘行, 岡部 博孝, Sanghyun Lee, Ping Miao, 鳥居 周輝, 神山 崇, 宮川 仁, 松下 能孝

  日本物理学会講演概要集 70 874 - 874 一般社団法人日本物理学会 2015年
• 17aCM-3 三角格子反強磁性体β'-LiCoPO_4 のμSR II

  岡部 博孝, 平石 雅俊, 山内 一宏, 竹下 聡史, 幸田 章宏, 小嶋 健児, 門野 良典, 吉田 紘行, 宮川 仁, 松下 能孝

  日本物理学会講演概要集 70 873 - 873 一般社団法人日本物理学会 2015年
• 22aPS-17 FeGe_<1-x>Si_x系B20型化合物におけるスキルミオン結晶のローレンツ電子顕微鏡観察

  肖 英紀, 長尾 全寛, 吉田 紘行, 長井 拓郎, 枝川 圭一, 齋藤 嘉一, 原 徹, 山崎 淳司, 木本 浩司

  日本物理学会講演概要集 70 2113 - 2113 一般社団法人日本物理学会 2015年
• 22aAH-8 三角格子反強磁性体β'-LiCoPO_4 のμSR

  岡部 博孝, 宮崎 正範, 平石 雅俊, 山内 一宏, 竹下 聡史, 幸田 章宏, 小嶋 健児, 門野 良典, 吉田 紘行, 宮川 仁, 松下 能孝

  日本物理学会講演概要集 70 1157 - 1157 一般社団法人日本物理学会 2015年
• 24pDC-4 STM/STSから見たBi2212のオーバードープ領域におけるギャップ構造

  岸 文香, 米川 雄太, 黒澤 徹, 桃野 直樹, 竹山 幸作, 吉田 紘行, 小田 研, 伊土 政幸

  日本物理学会講演概要集 70 2484 - 2484 一般社団法人日本物理学会 2015年
• 24pDC-3 STM/STSから見たアンダードープ領域におけるBi2212の電荷秩序と準粒子干渉

  米川 雄太, 板垣 征一朗, 岸 文香, 黒澤 徹, 桃野 直樹, 吉田 紘行, 竹山 幸作, 小田 研, 伊土 政幸

  日本物理学会講演概要集 70 2483 - 2483 一般社団法人日本物理学会 2015年
• 24aBJ-8 単結晶volborthiteの強磁場NMR III

  吉田 誠, 那波 和宏, 瀧川 仁, Jeong M., Kramer S., Horvatic M., Berthier C., 松井 一樹, 後藤 貴行, 木村 尚次郎, 佐々木 孝彦, 石川 孟, 山浦 淳一, 吉田 紘行, 岡本 佳比古, 広井 善二

  日本物理学会講演概要集 70 1237 - 1237 一般社団法人日本物理学会 2015年
• Transport properties of the metallic two-dimensional triangular antiferromagnet Ag2CrO2

  Takanori Kida, Akira Okutani, Hiroyuki Yoshida, Masayuki Hagiwara

  20TH INTERNATIONAL CONFERENCE ON MAGNETISM, ICM 2015 75 647 - 652 2015年 [査読有り][通常論文]
   

  We have investigated the magnetotransport properties of polycrystalline samples of Ag2CrO2, which is a metallic two-dimensional triangular antiferromagnetic compound (T-N similar to 24 K). The electrical resistivity of this compound displayed metallic behavior and an abrupt decrease at T-N. Below T-N, almost linear positive magnetoresistance was observed. On the other hand, just above T-N, a large negative magnetoresistance of -38% at 8 T was observed. The absolute value of the negative magnetoresistance decreases with increasing temperature. The Hall resistance showed a nonlinear behavior as a function of the magnetic field below T-N. These results suggest that the transport properties of Ag2CrO2 are closely related to its unusual antiferromagnetic spin-structure.
• SrAuSi3: A Noncentrosymmetric Superconductor

  Masaaki Isobe, Hiroyuki Yoshida, Koji Kimoto, Masao Arai, Eiji Takayama-Muromachi

  CHEMISTRY OF MATERIALS 26 6 2155 - 2165 2014年03月 [査読有り][通常論文]
   

  A novel strontium-gold silicide (SrAuSi3) was successfully synthesized for the first time using a high-pressure technique, at similar to 6 GPa. X-ray Rietveld analysis and scanning transmission electron microscopy studies clearly revealed that SrAuSi3 crystallizes in a BaNiSn3-type structure, in space group I4mm with the following lattice parameters: a = 4.4090(1) angstrom, and c = 9.9475(3) angstrom. The structure was found not to have inversion symmetry in real space. From direct measurements of polycrystalline SrAuSi3, the electrical resistivity was zero, the static magnetic susceptibility was almost a full volume Meissner diamagnetic signal, and the specific heat exhibited a sharp jump, all of which were accompanied by a phase transition due to bulk superconductivity at a critical temperature (T-C) of 1.54 K. The SrAuSi3 compound is the first noncentrosymmetric superconductor that includes Au as a principal constituent element.
• Bulk nature of layered perovskite iridates beyond the Mott scenario: An approach from a bulk-sensitive photoemission study

  A. Yamasaki, S. Tachibana, H. Fujiwara, A. Higashiya, A. Irizawa, O. Kirilmaz, F. Pfaff, P. Scheiderer, J. Gabel, M. Sing, T. Muro, M. Yabashi, K. Tamasaku, H. Sato, H. Namatame, M. Taniguchi, A. Hloskovskyy, H. Yoshida, H. Okabe, M. Isobe, J. Akimitsu, W. Drube, R. Claessen, T. Ishikawa, S. Imada, A. Sekiyama, S. Suga

  PHYSICAL REVIEW B 89 12 121111(R)  2014年03月 [査読有り][通常論文]
   

  We present genuine bulk Ir 5d j(eff) states of layered perovskite iridates obtained by hard-x-ray photoemission spectroscopy (HAXPES) with s- and p-polarized lights. HAXPES spectra of Sr2IrO4 and Ba2IrO4 are well reproduced by the quasiparticle density of states calculated by the local density approximation with dynamical mean-field theory (LDA + DMFT). It is demonstrated that the insulating nature of the iridates is triggered by antiferromagnetic correlation (Slater type) combined with electron correlation (Mott type). The extremely-lowenergy bulk-sensitive photoemission spectroscopy reveals "bad metallic" states in the paramagnetic phase of the iridates, suggesting strongly renormalized metallic states above the Neel temperature as predicted by the LDA + DMFT.
• Spin-Orbit-Coupling-Induced jeff States in Perovskite Iridates Studied by Photoemission Spectroscopy

  A. Yamasaki, O. Kirilmaz, A. Irizawa, A. Higashiya, T. Muro, H. Fujiwara, F. Pfaff, P. Scheiderer, J. Gabel, M. Sing, M. Yabashi, K. Tamasaku, A. Hloskovskyy, H. Okabe, H. Yoshida, M. Isobe, J. Akimitsu, W, Drube, T. Ishikawa, S. Imada, A. Sekiyama, R. Claessen, S. Suga

  JPS Conference Proceeding 3 013001  2014年 [査読有り][通常論文]
  
• Partially disordered spin structure in Ag2CrO2 studied with μ⁺SR

  J. Sugiyama, H. Nozaki, K. Miwa, H. Yoshida, M. Isobe, K. Prša, A.Amato, D. Andreica, M. Månsson

  Physical Review B 88 18 184417  2013年11月 [査読有り][通常論文]
   

  The magnetism of a metallic two-dimensional triangular antiferromagnetic (AF) compound, Ag2CrO2, has been investigated by muon-spin rotation and relaxation (mu+SR) using a powder sample in the temperature range between 1.8 and 40 K. Below T-N = 24 K, a muon-spin precession signal was clearly observed in the zero-field spectrum, indicating the formation of static AF order. It was also found that the internal field is temperature independent except for in the vicinity of T-N, as in the case for the susceptibility versus temperature curve. This suggests that the AF transition is induced by a first-order structural phase transition at T-N. Combining the mu+SR result with the prediction for muon sites in the lattice by first-principles calculations, a partially disordered AF state was found to be the most reasonable spin structure for Ag2CrO2.
• Magnetic structure of the metallic triangular antiferromagnet Ag2NiO2

  Hiroshi Nozaki, Martin Mansson, Bertrand Roessli, Vladimir Pomjakushin, Kazuya Kamazawa, Yutaka Ikedo, Henry E. Fischer, Thomas C. Hansen, Hiroyuki Yoshida, Zenji Hiroi, Jun Sugiyama

  JOURNAL OF PHYSICS-CONDENSED MATTER 25 28 286005  2013年07月 [査読有り][通常論文]
   

  The magnetic structure of the metallic antiferromagnet Ag2NiO2 with the Neel temperature T-N = 56 K has been investigated by means of a neutron diffraction technique using a powder sample in the temperature range between 5 and 65 K. The antiferromagnetic (AF) diffraction peaks are clearly observed below T-N and can be indexed with the propagation vector k = (1, 1/3, 1/2). Based on the results of both a representational analysis and a Rietveld refinement of the magnetic peaks, the AF spin structure is determined as an A-type AF structure with m(l) = m(0) cos (2 pi k.l), where m(l) is the moment at the lth Ni3+ site and m0 = (0.31, 0, 0.65) mu(B) at 5 K.
• Direct observation and dynamics of spontaneous skyrmion-like magnetic domains in a ferromagnet

  Masahiro Nagao, Yeong-Gi So, Hiroyuki Yoshida, Masaaki Isobe, Toru Hara, Kazuo Ishizuka, Koji Kimoto

  NATURE NANOTECHNOLOGY 8 5 325 - 328 2013年05月 [査読有り][通常論文]
   

  The structure and dynamics of submicrometre magnetic domains are the main factors determining the physical properties of magnetic materials(1,2). Here, we report the first observation of skyrmion-like magnetic nanodomains in a ferromagnetic manganite, La0.5Ba0.5MnO3, using Lorentz transmission electron microscopy (LTEM). The skyrmion-like magnetic domains appear as clusters above the Curie temperature. We found that the repeated reversal of magnetic chirality is caused by thermal fluctuation. The closely spaced clusters exhibit dynamic coupling, and the repeated magnetization reversal becomes fully synchronized with the same chirality. Quantitative analysis of such dynamics was performed by LTEM to directly determine the barrier energy for the magnetization reversal of skyrmion-like nanometre domains. This study is expected to pave the way for further investigation of the unresolved nature and dynamics of magnetic vortex-like nanodomains.
• A novel crystal polymorph of volborthite Cu3V2O7(OH)2・2H2O

  H. Ishikawa, J. Yamaura, Y. Okamoto, H. Yoshida, G. J. Nilsen, Z.Hiroi

  Acta Crystallographica C 68 I41 - I44 2012年07月 [査読有り][通常論文]
   

  A new polymorph of volborthite [tricopper(II) divanadium(V) heptaoxide dihydroxide dihydrate], Cu3V2O7(OH)(2)center dot 2H2O, has been discovered in a single crystal prepared by hydrothermal synthesis. X-ray analysis reveals that the monoclinic structure has the space group C2/c at room temperature, which is different from that of the previously reported C2/m structure. Both structures have Cu3O6(OH)2 layers composed of edge-sharing CuO4(OH)2 octahedra, with V2O7 pillars and water molecules between the layers. The Cu atoms occupy two and three independent crystallographic sites in the C2/m and C2/c structures, respectively, likely giving rise to different magnetic interactions between CuII spins in the kagome lattices embedded in the Cu3O6(OH)2 layers.
• Orbital switching in a frustrated magnet

  Hiroyuki Yoshida, Jun-ichi Yamaura, Masaaki Isobe, Yoshihiko Okamoto, Goran J. Nilsen, Zenji Hiroi

  NATURE COMMUNICATIONS 3 860  2012年05月 [査読有り][通常論文]
   

  The orbital is one of the four fundamental degrees of freedom in a solid, besides spin, charge and lattice. In transition metal compounds, it is usually the d orbitals which play deciding roles in determining the crystallographic and physical properties. Here we report the discovery of a unique structural transition in single crystals of the spin-1/2 quasi-kagome antiferromagnet volborthite, Cu3V2O7(OH)(2)center dot 2H(2)O, whereby the unpaired electron 'switches' from one d orbital to another upon cooling. This is not a conventional orbital order-disorder transition, but rather an orbital switching that has not previously been observed. The structural transition is found to profoundly affect the magnetic properties of volborthite, because magnetic interactions between Cu spins in the kagome lattice are considerably modified by the orbital switching. This finding provides us with an interesting example to illustrate the intimate interplay between the orbital degree of freedom and competing magnetic interactions in a frustrated magnet.
• The spin dynamics in distorted kagome lattices: a comparative Raman study

  D. Wulferding, P. Lemmens, H. Yoshida, Y. Okamoto, Z. Hiroi

  JOURNAL OF PHYSICS-CONDENSED MATTER 24 18 185602  2012年05月 [査読有り][通常論文]
   

  Despite the conceptional importance of realizing spin liquids in solid states only few compounds are known. On the other hand the effect of lattice distortions and anisotropies on the magnetic exchange topology and the fluctuation spectrum is an interesting problem. We compare the excitation spectra of the two s = 1/2 kagome lattice compounds, volborthite and vesignieite, using Raman scattering. We demonstrate that even small modifications of the crystal structure may have a huge effect on the phonon spectrum and low-temperature properties.
• Partially disordered state and spin-lattice coupling in an S=3/2 triangular lattice antiferromagnet Ag2CrO2

  M. Matsuda, C. de la Cruz, H. Yoshida, M. Isobe, R. S. Fishman

  PHYSICAL REVIEW B 85 14 1444097  2012年04月 [査読有り][通常論文]
   

  Ag2CrO2 is an S = 3/2 frustrated triangular lattice antiferromagnet without an orbital degree of freedom. With decreasing temperature, a four-sublattice spin state develops. However, a long-range partially disordered state with five sublattices abruptly appears at T-N = 24 K, accompanied by a structural distortion, and persists at least down to 2 K. The spin-lattice coupling stabilizes the anomalous state, which is expected to appear only in limited ranges of further-neighbor interactions and temperature. It was found that the spin-lattice coupling is a common feature in triangular lattice antiferromagnets with multiple-sublattice spin states, since the triangular lattice is elastic.
• High-Field Phase Diagram and Spin Structure of Volborthite Cu3V2O7(OH)2・2H2O

  M. Yoshida, M. Takigawa, S. Kramer, S. Mukhopadhyay, M. Horvati, C. Berthier, H. Yoshida, Y. Okamoto, Z. Hiroi

  Journal of the Physical Society of Japan 81 2 024703  2012年02月 [査読有り][通常論文]
   

  We report results of V-51 NMR experiments on a high-quality powder sample of volborthite Cu3V2O7(OH)(2)center dot 2H(2)O, a spin-1/2 Heisenberg antiferromagnet on a distorted kagome lattice. Following the previous experiments in magnetic fields B below 12 T, the NMR measurements have been extended to higher fields up to 31 T. In addition to the two already known ordered phases (phases I and II), we found a new high-field phase (phase III) above 25 T, at which a second magnetization step has been observed. The transition from the paramagnetic phase to the antiferromagnetic phase III occurs at 26 K, which is much higher than the transition temperatures from the paramagnetic to the lower field phases I (B < 4.5 T) and II (4.5 < B < 25 T). At low temperatures, two types of the V sites are observed with different relaxation rates and line shapes in phase III as well as in phase II. Our results indicate that both phases II and III exhibit a heterogeneous spin state consisting of two spatially alternating Cu spin systems, one of which exhibits anomalous spin fluctuations contrasting with the other showing a conventional static order. The magnetization of the latter system exhibits a sudden increase upon entering into phase III, resulting in the second magnetization step at 26 T. We discuss the possible spin structure in phase III.
• beta-Vesignieite BaCu3V2O8(OH)(2): a structurally perfect S=1/2 kagome antiferromagnet

  Hiroyuki Yoshida, Yuichi Michiue, Eiji Takayama-Muromachi, Masaaki Isobe

  JOURNAL OF MATERIALS CHEMISTRY 22 36 18793 - 18796 2012年 [査読有り][通常論文]
   

  A novel copper mineral beta-vesignieite BaCu3V2O8(OH)(2) with trigonal symmetry has been synthesized for the first time using a hydrothermal technique. beta-Vesignieite is an ideal spin-1/2 kagome antiferromagnet. Antiferromagnetic long-range order is found at 9 K, probably due to a finite Dzyaloshinski-Moriya interaction caused by the kagome symmetry.
• Novel S=3/2 Triangular Antiferromagnet Ag2CrO2 with Metallic Conductivity

  Hiroyuki Yoshida, Eiji Takayama-Muromachi, Masaaki Isobe

  JOURNAL OF THE PHYSICAL SOCIETY OF JAPAN 80 12 123703  2011年12月 [査読有り][通常論文]
   

  A novel metallic silver chromate, Ag2CrO2, was synthesized using a high-pressure technique. Ag2CrO2 crystallizes in trigonal symmetry with lattice parameters of a = 2.9271(1) angstrom and c = 8.6721(4) angstrom. The structure consists of CrO2 and double Ag layers stacked alternately along the c-axis. The former realizes an S = 3/2 triangular-lattice Heisenberg system, while the latter provides itinerant electrons. Ag2CrO2 exhibits an antiferromagnetic long-range order at T-N = 24K with the weak ferromagnetic moment. The resistivity shows a sudden drop at T-N, suggesting a large s-d interaction (RKKY interaction) between the Cr 3d localized spins on the triangular lattice and the Ag 5s itinerant electrons. The RKKY interaction is responsible for releasing the magnetic frustration and the three-dimensional long-range ordering at T-N.
• Heterogeneous spin state in the field-induced phase of volborthite as seen via V-51 nuclear magnetic resonance

  M. Yoshida, M. Takigawa, H. Yoshida, Y. Okamoto, Z. Hiroi

  PHYSICAL REVIEW B 84 2 020410  2011年07月 [査読有り][通常論文]
   

  We report results of V-51 NMR in the field-induced phase of volborthite Cu3V2O7(OH)(2).2H(2)O, a spin-1/2 antiferromagnet on a distorted kagome lattice. In magnetic fields above 4.5 T, two types of V sites with different spin-echo decay rates are observed. The hyperfine field at the fast decaying sites has a distribution, while it is more homogeneous at the slowly decaying sites. Our results indicate a heterogeneous state consisting of two spatially alternating Cu spin systems, one of which exhibits anomalous spin fluctuations contrasting with the other showing a conventional static order.
• Magnetization plateaus of the spin-1/2 kagome antiferromagnets volborthite and vesignieite

  Yoshihiko Okamoto, Masashi Tokunaga, Hiroyuki Yoshida, Akira Matsuo, Koichi Kindo, Zenji Hiroi

  PHYSICAL REVIEW B 83 18 180407  2011年05月 [査読有り][通常論文]
   

  The magnetization of two spin-1/2 kagome antiferromagnets, volborthite and vesignieite, has been measured in pulsed magnetic fields up to 68 T. A magnetization plateau is observed for each compound near the highest magnetic field. Magnetizations at saturation are approximately equal to 0.40 M-s for both compounds, where M-s is the fully saturated magnetization, irrespective of a difference in the distortion of the kagome lattice between the two compounds. It should be noted that these values of magnetizations are significantly larger than M-s/3 predicted theoretically for the one-third magnetization plateau in the spin-1/2 kagome antiferromagnet. The excess magnetization over M-s/3 is nearly equal to the sum of the magnetizations gained at the second and third magnetization steps in volborthite, suggesting that there is a common origin for the excess magnetization and the magnetization steps.
• Novel magnetic order in the kagome lattice of volborthite

  Zenji Hiroi, Hiroyuki Yoshida, Yoshihiko Okamoto, Makoto Yoshida

  INTERNATIONAL CONFERENCE ON FRUSTRATION IN CONDENSED MATTER (ICFCM) 320 012003  2011年 [査読有り][通常論文]
   

  The ground-state magnetic properties of the spin-1/2 quasi-kagome compound volborthite are discussed. Volborthite exhibits a peculiar phase transition to an unconventional ordered phase at 1 K. This phase is characterized by dense low-energy excitations and extremely slow spin fluctuations together with spin-wave like excitations, as evidenced by means of heat capacity and (51)V NMR. To understand these features, we consider an exotic long-range order based on the 120 degrees root 3 x root 3 spin structure, which allows local modes in the hexagons of the kagome lattice.
• Structural studies of a mixed-valence state in the incommensurate composite crystal Sr1.261CoO3

  Masaaki Isobe, Hiroyuki Yoshida, Eiji Takayama Muromachi, Kenji Ohoyama

  SCIENCE AND TECHNOLOGY OF ADVANCED MATERIALS 11 6 065004  2010年12月 [査読有り][通常論文]
   

  The incommensurate modulated crystal structure of the hexagonal cobalt oxide Sr1.261CoO3 has been studied using a four-dimensional (4D) superspace profile analysis of neutron powder diffraction data. Sr1.261CoO3 is a composite crystal that consists of the [CoO3] and [2Sr] subsystems. The [CoO3] subsystem forms 1D chains that run parallel to the c-axis and consist of face-sharing CoO6 polyhedra with octahedral (Oh) and trigonal prismatic (TP) coordinations. The structure analysis reveals that the [CoO3] chains contain 73.9% Oh and 26.1% TP sites, and that the TP sites have longer Co-O bonds than the Oh sites: d(av). = 2.039(4) angstrom (TP) and 1.895(3) angstrom (Oh). The averaged Co bond valences are Co3.56(3)+ in the Oh sites and Co2.45(3)+ in the TP sites, suggesting that a considerable amount of Co3+ ions are mixed with Co4+ ions in the Oh sites and with Co2+ ions in the TP sites. The observed magnetic susceptibility can be well explained assuming that the compound has the Co mixed-valence state with the spin configurations of S = 0 low-spin state for Co3+(d epsilon(6)), S = 1/2 low-spin state for Co4+(d epsilon(5)) and S = 3/2 high-spin state for Co2+(d epsilon(5)d gamma(2)). The Weiss temperature, approximately 0.8 K, implies that Sr1.261CoO3 naturally assumes a Curie paramagnetic state, probably owing to the obstruction of the intrachain magnetic interaction by the nonmagnetic Co3+ ions. These results suggest that the nonmagnetic Co3+ ions play an essential role in the magnetism of Sr2 gamma CoO3 systems.
• Thermodynamic Properties of the Kagome Lattice in Volborthite

  Satoshi Yamashita, Tomoya Moriura, Yasuhiro Nakazawa, Hiroyuki Yoshida, Yoshihiko Okamoto, Zenji Hiroi

  JOURNAL OF THE PHYSICAL SOCIETY OF JAPAN 79 8 083710  2010年08月 [査読有り][通常論文]
   

  Thermodynamic investigations on volborthite [Cu3V2O7(OH)(2)center dot 2H(2)O], which possesses a two-dimensional kagome structure of S-1/2 spins, are presented. The low-temperature heat capacities of volborthite and its Zn analogue compound were measured by the relaxation calorimetry technique between 0.8 and 45 K. The magnetic heat capacity of volborthite is characterized by two contributions of T-linear and T-2 dependences, the former of which is large above 1K, giving evidence of dense gapless excitations. We find a distinct kink in CpT-1 at T* = 1 K, which demonstrates a thermodynamic phase transition of short-range nature to a novel ground state as reported in previous V-51-NMR experiments. The T-linear term becomes smaller but remains finite even in the low-temperature state below T*, while it is gradually reduced with increasing magnetic field and vanishes at 5 T, which is close to the critical field for the field-induced transition observed in the first magnetization step.
• Spin dynamics of S=1/2 kagome basic solid state physics lattice antiferromagnets observed by high-field ESR

  Hitoshi Ohta, Wei-min Zhang, Susumu Okubo, Masashi Fujisawa, Takahiro Sakurai, Yoshihiko Okamoto, Hiroyuki Yoshida, Zenji Hiroi

  PHYSICA STATUS SOLIDI B-BASIC SOLID STATE PHYSICS 247 3 679 - 681 2010年03月 [査読有り][通常論文]
   

  Due to the existence of strong spin frustration in a system, the spin dynamics of S = 1/2 kagome lattice antiferromagnet at low temperature has attracted much interest. High-field ESR has been measured on its model substances, Cu(3)V(2)O(7)(OH)(2)center dot 2H(2)O (volborthite) and BaCu(3)V(2)O(3)(OH)(2) (vesignieite), down to 1.8K using pulsed magnetic fields up to 16T. The measurements are performed for 160 and 315 GHz using polycrystalline samples. Although both samples showed the g-shift and the change of linewidth at low temperature, volborthite showed a small gap excitation of the order of 40 GHz (1.9 K) while vesignieite showed a paramagnetic behavior down to 1.9 K. Observed difference will be discussed in connection with the crystal structure, and the possible spin liquid state in vesignieite will be discussed. (C) 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
• Orbital order and partial electronic delocalization in a triangular magnetic metal Ag2MnO2

  S. Ji, E. J. Kan, M. -H. Whangbo, J. -H. Kim, Y. Qiu, M. Matsuda, H. Yoshida, Z. Hiroi, M. A. Green, T. Ziman, S. -H. Lee

  PHYSICAL REVIEW B 81 9 094421  2010年03月 [査読有り][通常論文]
   

  Magnetic and electrical properties of Ag2MnO2 were examined by elastic and inelastic neutron-scattering measurements and by density-functional calculations. The spins of the triangular antiferromagnet metal Ag2MnO2 are found to freeze into a gapless short-range collinear state below 50 K because of a ferro-orbital ordering and spin-orbit coupling of the high-spin Mn3+ ions. The decrease in the spin-spin correlation lengths of Ag2MnO2 in the order, xi(b) >> xi(a) >> xi(c), is explained by the spin-exchange interactions calculated for the ferro-orbital ordered state. The electronic states around the Fermi level have significant contributions from the spin-polarized Mn 3d and O 2p states, which makes electron-electron scattering dominate over electron-phonon scattering at low temperatures leading to the rho proportional to T-2 behavior below 50 K.
• High-Field ESR Measurements of S=1/2 Kagome Lattice Antiferromagnet BaCu3V2O8(OH)(2)

  Wei-min Zhang, Hitoshi Ohta, Susumu Okubo, Masashi Fujisawa, Takahiro Sakurai, Yoshihiko Okamoto, Hiroyuki Yoshida, Zenji Hiroi

  JOURNAL OF THE PHYSICAL SOCIETY OF JAPAN 79 2 023708  2010年02月 [査読有り][通常論文]
   

  High-field electron spin resonance (ESR) measurements have been performed oil vesignieite BaCu3V2O8(OH)(2), which is considered as a nearly ideal model substance of S = 1/2 kagome antiferromagnet, in the temperature region from 1.9 to 265 K. The frequency region is from 60 to 360 GHz and the applied pulsed magnetic field is Up to 16 T. Observed g-value and linewidth show the increase below 20 K, which suggest the development of the short range order. Moreover. a gapless spin liquid ground State is suggested from the frequency-field relation at 1.9 K.
• Resonant Photoemission Spectroscopy of Layered Triangular Lattices Ag2MO2 (M = Ni and Mn): Evidence for M 3d States at Fermi Level

  Ritsuko Eguchi, Hiroyuki Yoshida, Yoshihiko Okamoto, Ashish Chainani, Masaharu Matsunami, Yukiaki Ishida, Masaki Oura, Yasunori Senba, Haruhiko Ohashi, Shik Shin, Zenji Hiroi

  JOURNAL OF THE PHYSICAL SOCIETY OF JAPAN 79 2 023704  2010年02月 [査読有り][通常論文]
   

  We report oil the soft X-ray photoemission and absorption spectroscopy of Ag2NiO2 and Ag2MnO2, which consist of' alternate stacks of (Ag-2)(+) and (MO2)(-) layers. The core-level photoemission and absorption spectra indicate mainly trivalent Ni3+ in Ag2NiO2, and trivalent Mn3+ With an admixture of Mn2+ states in Ag2MnO2. The M 2p-3d resonant photoemission clearly shows that the density of states at the Fermi level includes the M 3d character in both compounds. The results indicate that the Ni 3d and Mn 3d states at the Fermi level are responsible for the significant mass enhancement of carriers, as seen in the transport properties of Ag2NiO2 and Ag2MnO2.
• Phase Diagram and Spin Dynamics in Volborthite with a Distorted Kagome Lattice

  M. Yoshida, M. Takigawa, H. Yoshida, Y. Okamoto, Z. Hiroi

  PHYSICAL REVIEW LETTERS 103 7 077207  2009年08月 [査読有り][通常論文]
   

  We report a V-51-NMR study on a high-quality powder sample of volborthite Cu3V2O7(OH)(2) center dot 2H(2)O, a spin-1/2 Heisenberg antiferromagnet on a distorted kagome lattice formed by isosceles triangles. In the magnetic fields below 4.5 T, a sharp peak in the nuclear spin-lattice relaxation rate 1/T-1 accompanied with line broadening revealed a magnetic transition near 1 K. The low temperature phase shows anomalies such as a Lorentzian line shape, a 1/T-1 alpha T behavior indicating dense low-energy excitations, and a large spin-echo decay rate 1/T-2 pointing to unusually slow fluctuations. Another magnetic phase appears above 4.5 T with less anomalous spectral shape and dynamics.
• Magnetization "Steps" on a Kagome Lattice in Volborthite

  Hiroyuki Yoshida, Yoshihiko Okamoto, Takashi Tayama, Toshiro Sakakibara, Masashi Tokunaga, Akira Matsuo, Yasuo Narumi, Koichi Kindo, Makoto Yoshida, Masashi Takigawa, Zenji Hiroi

  JOURNAL OF THE PHYSICAL SOCIETY OF JAPAN 78 4 043704  2009年04月 [査読有り][通常論文]
   

  Magnetic properties of the spin-1/2 kagome-like compound volborthite are studied using a high-quality polycrystalline sample. It is evidenced from magnetization and specific heat measurements that the spins on the kagome lattice Still fluctuate at low temperature, down to T = 60 mK that corresponds to 1/1500 of the nearest-neighbor antiferromagnetic interaction, exhibiting neither a conventional long-range order nor a spin gap. In contrast, V-51 NMR experiments revealed a sharp peak at 1 K in relaxation rate, which indicates that a certain exotic order Occurs. Surprisingly, we have observed three "steps" in magnetization as a function of magnetic field, suggesting that at least four liquid-like or other quantum states exist under magnetic fields.
• Static magnetic order in metallic triangular antiferromagnet Ag2MnO2

  Jun Sugiyama, Hiroshi Nozaki, Yutaka Ikedo, Kazuhiko Mukai, Peter L. Russo, Daniel Andreica, Alex Amato, Hiroyuki Yoshida, Zenji Hiroi

  PHYSICA B-CONDENSED MATTER 404 5-7 777 - 780 2009年04月 [査読有り][通常論文]
   

  The magnetic nature of the triangular antiferromagnet Ag2MnO2, which exhibits two magnetic transitions at T-m1 similar to 80 K and T-m2 similar to 30 K, has been studied with mu+SR spectroscopy using a polycrystalline sample in the temperature (T) range between 300 and 1.8 K. Weak transverse field muon-spin rotation and relaxation (mu+SR) measurements suggest the appearance of a random internal magnetic field at T below T-m1, while zero field (ZF) mu+SR measurements indicate the existence of static internal magnetic fields below T-m2. Furthermore, two components with similar to 10 times different precession frequencies but almost equivalent amplitudes in the ZF-spectrum indicate the formation of a static but complex anti ferromagnetic order below T-m2. The overall magnetic behavior is therefore clarified in that the static disordered moments appear below T-m1, whereas the short-range order completes below T-m2 = T-N. (c) 2008 Elsevier B.V. All rights reserved.
• Vesignieite BaCu3V2O8(OH)(2) as a Candidate Spin-1/2 Kagome Antiferromagnet

  Yoshihiko Okamoto, Hiroyuki Yoshida, Zenji Hiroi

  JOURNAL OF THE PHYSICAL SOCIETY OF JAPAN 78 3 033701  2009年03月 [査読有り][通常論文]
   

  A polycrystalline sample of vesignicite BaCu3V2O8(OH)(2) comprising a nearly ideal kagome lattice composed of Cu2+ ions carrying spin 1/2 has been synthesized and studied by magnetization and heat capacity measurements. Magnetic susceptibility shows a neither long range order, a spin glass transition nor a spin gap down to 2 K, in spite of a moderately strong antiferromagnetic interaction of J/k(B) = 53 K between nearest-neighbor spins. A broad peak observed at a temperature corresponding to 0.4J in intrinsic magnetic Susceptibility indicates a marked development of the short-range order. The ground state of vesignicite is probably a gapless spin liquid or is accompanied by a very small gap less than similar to J/30.
• S = 1/2 kagome lattice antiferromagnet Cu3V2O7(OH)2・2H2O studied by high field ESR

  H. Ohta, W. Zhang, S. Okubo, M. Tomoo, M. Fujisawa, H. Yoshida, Y. Okamoto, Z. Hiroi

  Journal of Physics: Conference Series 145 012010  2009年 [査読有り][通常論文]
   

  X-band and high field electron spin resonance (ESR) measurements on S=1/2 kagome lattice antiferromagnet Cu3V2O7(OH)(2)center dot 2H(2)O (volborthite) have been performed. Although the kagome lattice is slightly deformed in the ab plane, no sign of magnetic order is observed down to 3.8 K, which is consistent with the magnetic susceptibility and the specific heat results, because the X-band ESR result shows no g-shift and the broadening of the linewidth down to 3.8 K. However, high field ESR results above 40 GHz show continuous g-shift below 20 K, which coincides with the broad maximum in the magnetic susceptibility. These results suggest the existence of the short range order and the field dependence in the system, and they are discussed inconnection with the recent magnetization result.
• Spin-1/2 kagome compounds: volborthite vs herbertsmithite

  Z. Hiroi, H. Yoshida, Y. Okamoto, M. Takigawa

  HIGHLY FRUSTRATED MAGNETISM 2008 (HFM 2008) 145 012002  2009年 [査読有り][通常論文]
   

  Two kagome compounds, volborthite Cu3V2O7(OH)(2)center dot 2H(2)O and herbertsmithite ZnCu3(OH)(6)Cl-2, are compared in order to derive information about the intrinsic properties of the spin-1/2 kagome antiferromagnet. Observed for volborthite are a broad maximum at T similar to J/4 and a large finite value approached at T = 0 in bulk magnetic susceptibility chi(bulk) as well as local one chi(local) from the NMR measurements. These must be the intrinsic properties for the spin-1/2 kagome antiferromagnet, as similar behavior was also reported in chi(local) for herbertsmithite [Olariu A et al. 2008 Phys. Rev. Lett., 100 087202]. Impurity effects that may influence seriously the bulk properties are discussed.
• Static magnetic order in metallic triangular antiferromagnet Ag(2)MnO(2) detected by muon-spin spectroscopy (vol 78, art no 104427, 2008)

  Jun Sugiyama, Hiroshi Nozaki, Yutaka Ikedo, Kazuhiko Mukai, Peter L. Russo, Daniel Andreica, Alex Amato, Hiroyuki Yoshida, Zenji Hiroi

  PHYSICAL REVIEW B 78 13 104427  2008年10月 [査読有り][通常論文]
  
• Unique phase transition on spin-2 triangular lattice of Ag2MnO2

  Hiroyuki Yoshida, Sascha Ahlert, Martin Jansen, Yoshihiko Okamoto, Jun-Ichi Yamaura, Zenji Hiroi

  JOURNAL OF THE PHYSICAL SOCIETY OF JAPAN 77 7 074719  2008年07月 [査読有り][通常論文]
   

  Ag2MnO2 is studied as a possible candidate compound for an antiferromagnetic XY spin model on a triangular lattice. In spite of the large Curie-Weiss temperature of -430 K found in magnetic susceptibility, Mn3+ spins with S = 2 do not undergo a conventional long-range order down to 2 K probably owing to the geometrical frustration and two dimensionality in the system. Instead, a unique phase transition is found at 80 K, where specific heat exhibits a clear sign of a second-order phase transition, while magnetic susceptibility changes smoothly without a distinct anomaly. We think that this transition is related to the chirality degree of freedom associated with a short-range order, which has been expected for the classical XY spin model on a triangular lattice. On further cooling, spin-glass-like behavior is observed below 22 K, possibly corresponding to a quasi-long-range order.
• Neutron diffraction study of layered Ni dioxides: Ag2NiO2

  Hiroshi Nozaki, Jun Sugiyama, Marc Janoschek, Bertrand Roessli, Vladimir Pomjakushin, Lukas Keller, Hiroyuki Yoshida, Zenji Hiroi

  JOURNAL OF PHYSICS-CONDENSED MATTER 20 10 104236  2008年03月 [査読有り][通常論文]
   

  In order to elucidate the antiferromagnetic (AF) nature of hexagonal Ag2NiO2 with T-N = 56 K and to know the mechanism of the structural phase transition of T-S similar to 270 K, neutron powder diffraction patterns have been measured in the temperature range between 1.5 and 330 K. One magnetic Bragg peak indexed as (1) (3) (1) (3) 0 is clearly observed below T-N, confirming the formation of long-range AF order, reported by a muon-spin spectroscopy measurement. The weak intensity of the magnetic peak also suggests the two-dimensional nature of the AF order, but the spin structure is still unknown. In addition, the precise structural analysis of the data between 160 and 330 K shows that only the c(H)-axis length changes drastically at T-S, which suggests the appearance of local Jahn-Teller distortion below T-S.
• Impurity effects on the Ni3+ triangular lattice of Ag2NiO2

  H. Yoshida, Y. Muraoka, Z. Hiroi

  JOURNAL OF PHYSICS-CONDENSED MATTER 19 14 145235  2007年04月 [査読有り][通常論文]
   

  Silver oxonickelate Ag2NiO2 is a metallic compound presenting a spin- 1/2 triangular lattice. It exhibits a structural transition at T-s = 260 K, which may be related to e(g) orbital ordering, and an antiferromagnetic transition at T-N = 55 K. Impurity effects on its magnetic and electronic properties are examined by substituting Fe for Ni in Ag2Ni1-xFexO2 ( 0 <= x <= 0.3). A Curielike enhancement in magnetic susceptibility is observed at low temperature, which implies that most Fe3+ spins behave as free spins. Moreover, a large enhancement of residual resistivity and its suppression under magnetic fields are observed. Magnetic interactions in the Ni3+ triangular lattice are discussed.
• Incommensurate magnetic order in Ag2NiO2 studied with muon-spin-rotation and relaxation spectroscopy

  J. Sugiyama, Y. Ikedo, K. Mukai, J. H. Brewer, E. J. Ansaldo, G. D. Morris, K. H. Chow, H. Yoshida, Z. Hiroi

  PHYSICAL REVIEW B 73 22 224437  2006年06月 [査読有り][通常論文]
   

  The nature of the magnetic transition of the half-filled triangular antiferromagnet Ag2NiO2 with T-N=56 K was studied with positive muon-spin-rotation and relaxation (mu+SR) spectroscopy. Zero field mu+SR measurements indicate the existence of a static internal magnetic field at temperatures below T-N. Two components with slightly different precession frequencies and wide internal-field distributions suggest the formation of an incommensurate antiferromagnetic order below 56 K. This implies that the antiferromagnetic interaction is predominant in the NiO2 plane in contrast to the case of the related compound NaNiO2. An additional transition was found at similar to 22 K by both mu+SR and susceptibility measurements. It was also clarified that the transition at similar to 260 K observed in the susceptibility of Ag2NiO2 is induced by a purely structural transition.
• Spin-1/2 triangular lattice with orbital degeneracy in a metallic oxide Ag2NiO2

  H Yoshida, Y Muraoka, T Sorgel, M Jansen, Z Hiroi

  PHYSICAL REVIEW B 73 2 020408(R)  2006年01月 [査読有り][通常論文]
   

  A metallic and magnetic transition metal oxide Ag2NiO2 is studied by means of resistivity, magnetic susceptibility, specific heat, and x-ray diffraction. The crystal structure is characterized by an alternating stacking of a Ni3+O2 layer and a (Ag-2)(+) layer, the former realizing a spin-1/2 triangular lattice with e(g) orbital degeneracy and the latter providing itinerant electrons. It is found that the NiO2 layer exhibits orbital ordering at T-s = 260 K and antiferromagnetic spin ordering at T-N= 56 K. Moreover, a moderately large mass enhancement is found for the itinerant electrons, suggesting a significant contribution from the nearly localized Ni 3d state to the Ag 5s state that forms a broad band.
• Spin-1/2 triangular laiftice in Ag2NiO2

  Hiroyuki Yoshida, Yuji Muraoka, Zenji Hiroi, Timo Soergel, Martin Jansen

  LOW TEMPERATURE PHYSICS, PTS A AND B 850 1089 - + 2006年 [査読有り][通常論文]
   

  A novel metallic compound with a spin-1/2 triangular lattice is reported. It is a silveroxonickelate Ag2NiO2 containing a NiO2 layer which possesses a spin-1/2 triangular lattice with twofold spin and twofold orbital degeneracy. It is found that a structural transition takes place at T-s = 260 K, which may be related to orbital ordering, and long-range antiferromagnetic order sets in below T-N = 54 K.

書籍

• 極低温まで凍結しないスピンの動的性質の観測

  吉田紘行, 井原慶彦, 岡部博孝, 幸田章宏, 門野良典 (担当:共著)
  アグネ 技術センター 2022年09月

講演・口頭発表等

• Exploring of the new materials without time- and spatial-inversion symmetry  [招待講演]

  吉田紘行

  第29回日本MRS年次大会 2019年11月 口頭発表（招待・特別）
• Application of hydrothermal technique to develop 3d transition metal compounds without local inversion symmetry  [招待講演]

  吉田紘行

  J-Physics 2019 International Conference 2019年09月 口頭発表（招待・特別）
• Dual magnetic excitations in S = 1/2 kagome antiferromagnet CaCu3(OH)6Cl2•0.6H2O  [招待講演]

  吉田紘行

  International workshop on topological quantum materials 2019 2019年01月 口頭発表（招待・特別）
• Unusual magnetic ground state with dual magnetic excitations in S = 1/2 J1-J2-Jd kagome antiferromagnet CaCu3(OH)6Cl2•0.6H2O  [招待講演]

  吉田紘行

  4th International Conference on Functional Materials Science 2018 2018年11月 口頭発表（招待・特別）
• S = 3/2ブリージングカゴメ格子反強磁性体Li2Cr3SbO8の磁性  [招待講演]

  吉田紘行

  スピン系物理研究会 2018年11月 口頭発表（招待・特別）
• カゴメ反強磁性体の強磁場磁化過程の実験的研究  [招待講演]

  吉田紘行

  基研研究会”スピン系物理の最前線” 2018年10月 口頭発表（招待・特別）
• S = 1/2擬一次元ボンド交替ハイゼンベルク反強磁性鎖CaCu2(OH)3Cl3の磁性  [招待講演]

  吉田紘行

  第5回西日本強磁場科学研究会 2018年09月 口頭発表（招待・特別）
• Material development towards the perfect frustration on kagome antiferromagnet  [招待講演]

  吉田紘行

  J-Physics 2018: International Workshop on New Materials and Crystal Growth 2018年06月 口頭発表（招待・特別）
• Quantum Spin Liquid in S = 1/2 Kagome Lattice Antiferromagnet CaCu3(OH)6Cl2•0.6H2O  [招待講演]

  吉田紘行

  International Conference IUMRS-ICAM 2017, Symposium, Frontiers of the functional development of strongly correlated materials 2017年09月 口頭発表（招待・特別）
• Unusual magnetic state in S = 1/2 J1-J2-Jd kagome lattice antiferromagnet CaCu3(OH)6Cl2•0.6H2O  [招待講演]

  吉田紘行

  1st Asia Pacific Workshop on Quantum Magnetism 2017年08月 口頭発表（招待・特別）
• Frustrated magnetism of kagome lattice antiferromagnet  [招待講演]

  吉田紘行

  International symposium Challenges and progress in strongly correlated functional materials, MRS-Japan 2015年12月 口頭発表（招待・特別）
• Orbital Switching Phenomenon in Spin-1/2 Kagome Antiferromagnet Volborthite  [通常講演]

  吉田紘行

  Study of Matter at Extreme Conditions 2015 2015年03月 口頭発表（招待・特別）
• Orbital Switching Found in Spin-1/2 Kagome Antiferromagnet Volborthite  [通常講演]

  吉田紘行

  International Conference on Highly Frustrated Magnetism 2012 2012年06月 口頭発表（一般）
• 古典三角格子反強磁性体Ag₂MO₂ (M = Cr, Fe)の合成と物性  [招待講演]

  吉田紘行

  第39回化合物新磁性材料専門研究会 2010年12月 口頭発表（招待・特別）
• Magnetization steps on the spin liquid ground state of the S = 1/2 kagome-like antiferromagnet Cu3V2O7(OH)2•2H2O  [通常講演]

  H. Yoshida, Z. Hiroi

  American Physical Society 2009 March Meeting 2009年03月 口頭発表（一般）

その他活動・業績

• スピン1/2カゴメ反強磁性体CaCu₃(OD)₆Cl₂・0.6D₂Oにおけるq=0長距離磁気秩序

  飯田一樹, 吉田紘行, 中尾朗子, JESCHKE Harald O., IQBAL Yasir, 中島健次, 河村聖子, 宗像孝司, 稲村泰弘, 村井直樹, 石角元志, 熊井玲児, 熊井玲児, 岡田武久, 小田研, 加倉井和久, 松田雅昌 日本物理学会講演概要集(CD-ROM) 76 (1) 2021年
• 三角格子反強磁性体Ag₂CrO₂高純度薄膜における磁気異方性の電気的検出

  今田絵理阿, 谷口祐紀, 渡邉杜, 徳田将志, 鈴木将太, 井邊昂志, 荒川智紀, 荒川智紀, 吉田紘行, 石塚大晃, 小林研介, 小林研介, 新見康洋, 新見康洋 日本物理学会講演概要集(CD-ROM) 75 (1) 2020年
• 強磁場NMR測定によるS=3/2Crカゴメ反強磁性体における1/9磁化プラトー状態の研究

  井原慶彦, 荒島洸樹, 平田倫啓, 佐々木孝彦, 吉田紘行 東北大学金属材料研究所強磁場超伝導材料研究センター年次報告 2018 74 2019年06月 [査読無し][通常論文]
  
• ⁷Li NMR法による高磁場におけるLi₂Cr₃SbO₈の磁気状態の研究

  荒島洸樹, 井原慶彦, 佐々木孝彦, 平田倫啓, 吉田紘行 日本物理学会講演概要集(CD-ROM) 74 (1) ROMBUNNO.14aF303‐1 2019年03月22日 [査読無し][通常論文]
  
• 三角格子反強磁性体Ag₂CrO₂薄膜における磁気伝導測定

  谷口祐紀, 渡邉杜, 徳田将志, 井邊昂志, 鈴木将太, 荒川智紀, 荒川智紀, 吉田紘行, 石塚大晃, 小林研介, 小林研介, 新見康洋, 新見康洋 日本物理学会講演概要集(CD-ROM) 74 (2) 2019年
• カゴメ反強磁性体Caカペラサイトにおけるギャップレス磁気励起の観測

  井原慶彦, 佐々木孝彦, 野口直彌, 石井裕人, 小田研, 吉田紘行 Selected Topics Research Highlight at HFLSM 2017 5 2018年10月 [査読無し][通常論文]
  
• S=1/2カゴメ格子反強磁性体Ca‐kapellasiteの圧力下の磁性

  鈴木哲平, 齋藤佑, 原茂生, 櫻井敬博, 大久保晋, 太田仁, 赤木暢, 鳴海康雄, 萩原政幸, 吉田紘行 日本物理学会講演概要集(CD-ROM) 73 (2) ROMBUNNO.9aPS‐65 -513 2018年09月21日 [査読無し][通常論文]
  
• 三角格子反強磁性体Li₂AMo₃O₈(A=In,Sc)のμSR

  岡部博孝, 飯田一樹, 梶本亮一, 吉田紘行, 石井裕人, 村井直樹, 石角元志, 稲村泰弘, 中島健次, 幸田章宏, 幸田章宏, 平石雅俊, 竹下聡史, 竹下聡史, 小嶋健児, 小嶋健児, 門野良典, 門野良典 日本物理学会講演概要集(CD-ROM) 73 (2) 2018年
• カゴメ格子反強磁性体Li₂Cr₃SbO₈の磁性

  石井裕人, 吉田紘行, 小田研, 木田孝則, 鳴海康雄, 萩原政幸 セラミックス基礎科学討論会講演要旨集 56th 2018年
• S=5/2三角格子ダイマーCs₃Fe₂Cl₉の磁気相図 II

  石井裕人, 松下能孝, 吉田紘行, 小田研, 萩原雅人, 益田隆嗣, 木田孝則, 鳴海康雄, 萩原政幸 日本物理学会講演概要集(CD-ROM) 72 (2) ROMBUNNO.21aPS‐20 -644 2017年09月25日 [査読無し][通常論文]
  
• 擬カゴメ格子反強磁性体CdCu₃(OH)₆Cl₂の1/3磁化プラトー

  吉田紘行, 野口直彌, 石井裕人, 小田研, CHEN J, 山浦一成, 木田孝則, 鳴海康雄, 萩原政幸 日本物理学会講演概要集(CD-ROM) 72 (2) ROMBUNNO.22aE20‐2 -778 2017年09月25日 [査読無し][通常論文]
  
• 二次元三角格子反強磁性体Ag₂CrO₂の強磁場輸送現象

  浅岡俊介, 木田孝則, 奥谷顕, 吉田紘行, 萩原政幸 日本物理学会講演概要集(CD-ROM) 72 (1) ROMBUNNO.17pC‐PS‐8 -1088 2017年03月21日 [査読無し][通常論文]
   

  Ag_2_CrO_2_はAg_2_非磁性伝導層とCr^3+^(S=3/2)の三角格子を形成するCrO_2_磁性絶縁層が交互に積層した二次元反強磁性体である。電気抵抗がT_N_=24Kで急激な減少を示すことから，伝導電子とCr^3+^の局在スピン間に強い結合があることが予想される。今回，パルス磁場下での磁気伝導測定を行ったところ，低温で磁気抵抗のヒステリシスを伴う変化が観測された。講演では，この物質の磁性と伝導について議論する。(172文字)

• S=1/2カゴメ格子反強磁性体CaCu₃(OH)₆Cl₂・0.6H₂Oの³⁵Cl‐NMRによる研究

  吉田紘行, 井原慶彦, 野口直彌, 石井裕人, 高田篤, 木田孝則, 鳴海康雄, 萩原政幸, 河本充司, 佐々木孝彦, 小田研 日本物理学会講演概要集(CD-ROM) 72 (1) ROMBUNNO.19pC31‐9 -1247 2017年03月21日 [査読無し][通常論文]
   

  CaCu_3_(OH)_6_Cl_2_・0.6H_2_OはS = 1/2カゴメ格子反強磁性体の良いモデル物質である。本講演では、19 Tまでの粉末強磁場NMR、5.5 Tまでの単結晶NMRの結果を報告し、CaCu_3_(OH)_6_Cl_2_・0.6H_2_Oの基底状態について議論する。

• S=5/2三角格子ダイマーCs₃Fe₂Cl₉の磁気相図

  石井裕人, 松下能孝, 吉田紘行, 小田研, 高田篤, 木田孝則, 鳴海康雄, 萩原政幸 日本物理学会講演概要集(CD-ROM) 71 (2) ROMBUNNO.13pAA‐7 2016年09月23日 [査読無し][通常論文]
  
• S=1/2カゴメ格子反強磁性体CaCu₃(OH)₆Cl₂・0.6H₂O単結晶の磁性

  吉田紘行, 野口直彌, 石井祐人, 片岡萌子, 小田研, 岡部博孝, 岡部博孝, 飯田一樹, 山下智史, 中澤康浩, 高田篤, 木田孝則, 鳴海康雄, 萩原政幸 日本物理学会講演概要集(CD-ROM) 71 (2) ROMBUNNO.16aAG‐14 -1024 2016年09月23日 [査読無し][通常論文]
   

  我々はS = 1/2カゴメ格子反強磁性体CaCu_3_(OH)_6_Cl_2_・0.6H_2_Oの単結晶育成に成功した。T^*^ = 7 Kに磁気秩序の形成を示唆する磁化、比熱の異常が観測された。また、比熱には温度比例項が存在し、何らかの特異な磁気励起の存在が示唆される。当日は、単結晶を用いた結晶構造解析、磁化、比熱、強磁場磁化測定の結果について報告し、本物質の特異な磁性について議論する予定である。

• S=3/2カゴメ格子反強磁性体Li₂Cr₃SbO₈の1/9磁化プラトー

  石井裕人, 吉田紘行, 小田研, 岡部博孝, 岡部博孝, 飯田一樹, 高田篤, 木田孝則, 鳴海康雄, 萩原政幸 日本物理学会講演概要集(CD-ROM) 71 (2) ROMBUNNO.16aAG‐10 -1020 2016年09月23日 [査読無し][通常論文]
   

  今回我々は、S = 3/2カゴメ格子反強磁性体Li_2_Cr_3_SbO_8_の粉末試料を用いた磁化、比熱、強磁場磁化過程の測定を行った。T^*^ =4 Kにおいて磁気状態の形成を示唆する磁化、比熱の異常が観測され、強磁場磁化測定からはT^*^以下で1/9磁化プラトーが観測された。本公演では、以上の実験結果を詳細に報告するとともに、その磁性について議論する。

• S=3/2カゴメ格子反強磁性体Li₂Cr₃SbO₈のμSR

  岡部博孝, 岡部博孝, 竹下聡史, 平石雅俊, 幸田章宏, 幸田章宏, 小嶋健児, 小嶋健児, 門野良典, 門野良典, 石井裕人, 小田研, 吉田紘行 日本物理学会講演概要集(CD-ROM) 71 (2) 2016年
• 二次元三角格子反強磁性体Ag₂CrO₂の磁気輸送現象

  木田孝則, 奥谷顕, 浅岡俊介, 吉田紘行, 萩原政幸 日本物理学会講演概要集(CD-ROM) 70 (2) ROMBUNNO.16APS-93 2015年09月24日 [査読無し][通常論文]
  
• リチウムコバルトリン酸化合物の磁気状態

  岡部博孝, 岡部博孝, 宮崎正範, 平石雅俊, 山内一宏, 竹下聡史, 幸田章宏, 幸田章宏, 小嶋健児, 小嶋健児, 門野良典, 門野良典, 吉田紘行, 宮川仁, 松下能孝 物構研サイエンスフェスタ要旨集 3rd 36 2015年 [査読無し][通常論文]
  
• 7aPS-134 β'-LiCoPO_4の磁気物性(7aPS 領域3ポスターセッション(遍歴・化合物・酸化物・f電子系磁性,スピングラス,量子スピン,フラストレーション,磁気共鳴),領域3(磁性))

  岡部 博孝, 吉田 紘行, 宮川 仁, 松下 能孝, 宮崎 正範, 平石 雅俊, 山内 一宏, 竹下 聡史, 幸田 章宏, 小嶋 健児, 門野 良典 日本物理学会講演概要集 69 (2) 262 -262 2014年08月22日
• 10aBC-2 単結晶volborthiteの強磁場NMR II(10aBC フラストレーション(籠目格子),領域3(磁性))

  吉田 誠, 那波 和宏, 瀧川 仁, Jeong M., Kramer S., Horvatic M., Berthier C., 松井 一樹, 後藤 貴行, 木村 尚次郎, 佐々木 孝彦, 石川 孟, 山浦 淳一, 吉田 紘行, 岡本 佳比古, 広井 善二 日本物理学会講演概要集 69 (2) 311 -311 2014年08月22日
• 単結晶volborthieteの強磁場NMR II

  吉田誠, 那波和宏, 瀧川仁, JEONG M, KRAEMER S, HORVATIC M, BERTHIER C, 松井一樹, 後藤貴行, 木村尚次郎, 佐々木孝彦, 石川孟, 山浦淳一, 吉田紘行, 岡本佳比古, 広井善二 日本物理学会講演概要集 69 (2) 311 2014年08月22日 [査読無し][通常論文]
  
• STM/STSから見たアンダードープ領域におけるBi2212の電荷秩序と擬ギャップ

  板垣征一朗, 黒澤徹, 米川雄太, 竹山幸作, 桃野直樹, 吉田紘行, 小田研, 伊土政幸 日本物理学会講演概要集 69 (2) 320 -320 2014年08月22日 [査読無し][通常論文]
  
• β’‐LiCoPO₄の磁気物性

  岡部博孝, 吉田紘行, 宮川仁, 松下能孝, 宮崎正範, 平石雅俊, 山内一宏, 竹下聡史, 幸田章宏, 小嶋健児, 門野良典 日本物理学会講演概要集 69 (2) 262 2014年08月22日 [査読無し][通常論文]
  
• STM/STSからみたBi2212の超伝導に対するNi不純物効果

  浦田理礼, 柴田悠人, 黒澤徹, 吉田紘行, 桃野直樹, 小田研, 伊土政幸 日本物理学会講演概要集 69 (2) 421 -421 2014年08月22日 [査読無し][通常論文]
  
• STM/STSから見たBi2212の1次元変調構造とギャップサイズの相関

  野並拓矢, 吉田紘行, 岸文香, 黒澤徹, 戸田泰則, 竹山幸作, 小田研, 伊土政幸 日本物理学会講演概要集 69 (2) 421 -421 2014年08月22日 [査読無し][通常論文]
  
• FeGe系B20型化合物中のスキルミオン形成における元素置換効果

  SO Yeong‐Gi, 長尾全寛, 吉田紘行, 長井拓郎, 枝川圭一, 齋藤嘉一, 原徹, 山崎淳司, 木本浩司 日本物理学会講演概要集 69 (2) 433 -433 2014年08月22日 [査読無し][通常論文]
  
• 空間反転対称性の破れた新しい超伝導体SrAuSi₃

  磯部雅朗, 吉田紘行, 木本浩司, 新井正男, 室町英治 日本物理学会講演概要集 69 (1) 673 -673 2014年03月05日 [査読無し][通常論文]
  
• 二次元三角格子反強磁性体Ag₂CrO₂の強磁場磁性

  奥谷顕, 木田孝則, 吉田紘行, 萩原政幸 日本物理学会講演概要集 69 (1) 496 -496 2014年03月05日 [査読無し][通常論文]
  
• 高圧合成の新物質Ag₂FeO₂とAg₂CrO₂の積層不整

  磯部雅朗, 小野田みつ子, 吉田紘行 日本結晶学会年会講演要旨集 2014 54 2014年 [査読無し][通常論文]
  
• 金属伝導を示す三角格子反強磁性体Ag₂CrO₂のμ⁺SR

  杉山純, 野崎洋, 吉田紘行, 磯部雅朗, MANSSON Martin, PRSA Krunoslav, ANDREICA Daniel, AMATO Alex 日本物理学会講演概要集 68 (2) 448 -448 2013年08月26日 [査読無し][通常論文]
  
• 単結晶volborthiteの強磁場NMR

  吉田誠, 那波和宏, 瀧川仁, JEONG M, KRAEMER S, HORVATIC M, BERTHIER C, 石川孟, 山浦淳一, 吉田紘行, 岡本佳比古, 広井善二 日本物理学会講演概要集 68 (2) 404 -404 2013年08月26日 [査読無し][通常論文]
  
• NMRで見たvolborthiteの構造と磁性

  吉田誠, 石川孟, 山浦淳一, 吉田紘行, 岡本佳比古, 那波和宏, 瀧川仁, 広井善二 日本物理学会講演概要集 68 (2) 404 -404 2013年08月26日 [査読無し][通常論文]
  
• YbB₂C₂の単結晶育成と物性評価

  岡部博孝, 吉田紘行, 磯部雅朗, 松下能孝, 佐藤晃, 室町英治, 秋光純 日本物理学会講演概要集 68 (2) 464 2013年08月26日 [査読無し][通常論文]
  
• 空間反転対称性の破れた超伝導体Ag₂Pd₃Sの物性

  吉田紘行, 岡部博孝, 松下能孝, 室町英治, 磯部雅朗 日本物理学会講演概要集 68 (2) 531 -531 2013年08月26日 [査読無し][通常論文]
  
• 26aXY-4 単結晶volborthiteのNMR III(26aXY カゴメ格子・スピングラス,領域3(磁性,磁気共鳴))

  吉田 誠, 瀧川 仁, 石川 孟, 吉田 紘行, 山浦 淳一, 岡本 佳比古, 広井 善二 日本物理学会講演概要集 68 (1) 495 -495 2013年03月26日
• 単結晶volborthiteのNMR III

  吉田誠, 瀧川仁, 石川孟, 吉田紘行, 山浦淳一, 岡本佳比古, 広井善二 日本物理学会講演概要集 68 (1) 495 2013年03月05日 [査読無し][通常論文]
  
• 歪んだカゴメ格子反強磁性体ボルボサイト単結晶の磁化率および比熱の磁場方向依存性

  石川孟, 岡本佳比古, 山浦淳一, 吉田紘行, 広井善二 日本物理学会講演概要集 68 (1) 495 2013年03月05日 [査読無し][通常論文]
  
• 20aCD-8 単結晶volborthiteのNMR II(20aCD フラストレーション系(カゴメ・チューブ・ハニカム),領域3(磁性,磁気共鳴))

  吉田 誠, 瀧川 仁, 石川 孟, 吉田 紘行, 山浦 淳一, 岡本 佳比古, 広井 善二 日本物理学会講演概要集 67 (2) 430 -430 2012年08月24日
• 単結晶volborthiteのNMR II

  吉田誠, 瀧川仁, 石川孟, 吉田紘行, 山浦淳一, 岡本佳比古, 広井善二 日本物理学会講演概要集 67 (2) 430 2012年08月24日 [査読無し][通常論文]
  
• 25aBG-9 単結晶volborthite Cu_3V_2O_7(OH)_2・2H_2OのNMR(25aBG フラストレーション系(カゴメ格子),領域3(磁性,磁気共鳴))

  吉田 誠, 瀧川 仁, 石川 孟, 吉田 紘行, 山浦 淳一, 岡本 佳比古, 広井 善二 日本物理学会講演概要集 67 (1) 511 -511 2012年03月05日
• 25aBG-5 S=1/2カゴメ格子反強磁性体BaCu_3V_2O_8(OH)_2(β-vesignieite)の構造と磁性(25aBG フラストレーション系(カゴメ格子),領域3(磁性,磁気共鳴))

  吉田 紘行, 道上 勇一, 磯部 雅朗 日本物理学会講演概要集 67 (1) 510 -510 2012年03月05日
• 歪んだカゴメ格子反強磁性体volborthite単結晶の構造と物性

  石川孟, 岡本佳比古, 山浦淳一, 吉田紘行, NILSEN G. J, 広井善二 日本物理学会講演概要集 67 (1) 510 -510 2012年03月05日 [査読無し][通常論文]
  
• S=1/2カゴメ格子反強磁性体BaCu₃V₂O₈(OH)₂(β‐vesignieite)の構造と磁性

  吉田紘行, 道上勇一, 磯部雅朗 日本物理学会講演概要集 67 (1) 510 2012年03月05日 [査読無し][通常論文]
  
• S=1/2カゴメ格子反強磁性体のESRによる研究

  太田仁, 大久保晋, ZHANG W, 櫻井敬博, 岡本佳比古, 広井善二, 吉田紘行 日本物理学会講演概要集 67 (1) 511 -511 2012年03月05日 [査読無し][通常論文]
  
• 単結晶volborthite Cu₃V₂O₇(OH)₂・2H₂OのNMR

  吉田誠, 瀧川仁, 石川孟, 吉田紘行, 山浦淳一, 岡本佳比古, 広井善二 日本物理学会講演概要集 67 (1) 511 2012年03月05日 [査読無し][通常論文]
  
• S=1/2カゴメ格子反強磁性体Volborthite単結晶の極低温磁化測定

  榊原俊郎, 三田村裕幸, 山浦淳一, 岡本佳比古, 広井善二, 吉田紘行, 磯部雅朗 日本物理学会講演概要集 67 (1) 511 -511 2012年03月05日 [査読無し][通常論文]
  
• スピン1/2カゴメ格子反強磁性体Vesignieite BaCu₃V₂O₈(OH)₂の磁化と比熱

  岡本佳比古, 吉田誠, 瀧川仁, 吉田紘行, 広井善二 日本物理学会講演概要集 66 (2) 436 -436 2011年08月24日 [査読無し][通常論文]
  
• S=1/2カゴメ格子反強磁性体volborthite単結晶における物性 II

  山浦淳一, 吉田紘行, 磯部雅朗, 岡本佳比古, 広井善二 日本物理学会講演概要集 66 (2) 439 -439 2011年08月24日 [査読無し][通常論文]
  
• S=1/2カゴメ格子反強磁性体volborthite単結晶における物性 I

  吉田紘行, 山浦淳一, 磯部雅朗, 岡本佳比古, 広井善二 日本物理学会講演概要集 66 (2) 439 -439 2011年08月24日 [査読無し][通常論文]
  
• スピン1/2カゴメ格子反強磁性体vesignieite BaCu₃V₂O₈(OH)₂のNMR

  吉田誠, 岡本佳比古, 吉田紘行, 瀧川仁, 広井善二 日本物理学会講演概要集 66 (2) 436 2011年08月24日 [査読無し][通常論文]
  
• S=1/2カゴメ格子反強磁性体の強磁場ESRによる研究 II

  ZHANG W, 大久保晋, 太田仁, 櫻井敬博, 岡本佳比古, 広井善二, 吉田紘行 日本物理学会講演概要集 66 (2) 399 -399 2011年08月24日 [査読無し][通常論文]
  
• ボルボサイトCu₃V₂O₇(OH)₂・2H₂Oの強磁場中ミュオンスピン回転による磁場誘起磁気相転移の研究 II

  幸田章宏, 宮崎正範, 平石雅俊, 小嶋健児, 門野良典, 吉田紘行, 岡本佳比古, 広井善二 日本物理学会講演概要集 66 (2) 409 -409 2011年08月24日 [査読無し][通常論文]
  
• 古典三角格子反強磁性体Ag₂MO₂(M=Cr,Fe)の合成と物性

  吉田紘行 化合物新磁性材料専門研究会資料 (10) 13 2011年03月16日 [査読無し][通常論文]
  
• 26aHE-11 Cu_3V_2O_7(OH)_2・2H_2O(volborthite)のおそいゆらぎ(26aHE 磁性一般・測定技術開発・フラストレーション系,領域3(磁性,磁気共鳴))

  吉田 誠, 瀧川 仁, 吉田 紘行, 岡本 佳比古, 広井 善二 日本物理学会講演概要集 66 (1) 481 -481 2011年03月03日
• カゴメ格子磁性体Cu₃V₂O₇(OH)₂・2H₂Oのサブミリ波ESR II

  張衛民, 大久保晋, 太田仁, 藤澤真士, 櫻井敬博, 岡本佳比古, 広井善二, 吉田紘行 日本物理学会講演概要集 66 (1) 468 -468 2011年03月03日 [査読無し][通常論文]
  
• 古典三角格子反強磁性体Ag₂MO₂(M=Cr,Fe)の合成と物性

  吉田紘行, 磯部雅朗, 室町英治 日本物理学会講演概要集 66 (1) 465 -465 2011年03月03日 [査読無し][通常論文]
  
• Cu₃V₂O₇(OH)₂・2H₂O(volborthite)のおそいゆらぎ

  吉田誠, 瀧川仁, 吉田紘行, 岡本佳比古, 広井善二 日本物理学会講演概要集 66 (1) 481 2011年03月03日 [査読無し][通常論文]
  
• ボルボサイトCu₃V₂O₇(OH)₂・2H₂Oの強磁場中ミュオンスピン回転による磁場誘起磁気相転移の研究

  幸田章宏, 宮崎正範, 平石雅俊, 小嶋健児, 門野良典, 吉田紘行, 岡本佳比古, 広井善二 日本物理学会講演概要集 66 (1) 474 -474 2011年03月03日 [査読無し][通常論文]
  
• Sr₂Ir_1-xRh_xO₄における光学測定から見たスピン・軌道相互作用 II

  入澤明典, 磯山悟朗, 磯部雅朗, 吉田紘行, 飯塚拓也, 森龍也, 木村真一 日本物理学会講演概要集 66 (1) 623 -623 2011年03月03日 [査読無し][通常論文]
  
• 24pWL-5 Cu_3V_2O_7(OH)_2・2H_2O(volborthite)の強磁場磁気相図(24pWL フラストレーション系(カゴメ格子,理論),領域3(磁性,磁気共鳴))

  吉田 誠, 瀧川 仁, Kramer S., Mukhopadhyay S., Horvatic M., Berthier C., 吉田 紘行, 岡本 佳比古, 広井 善二 日本物理学会講演概要集 65 (2) 387 -387 2010年08月18日
• S=5/2三角格子反強磁性体Ag₂FeO₂の合成と物性

  吉田紘行, 磯部雅朗, 室町英治 日本物理学会講演概要集 65 (2) 396 -396 2010年08月18日 [査読無し][通常論文]
  
• Sr₂Ir_1-xRh_xO₄における光学測定から見たスピン・軌道相互作用

  入澤明典, 磯部雅朗, 吉田紘行, 飯塚拓也, 木村真一 日本物理学会講演概要集 65 (2) 485 -485 2010年08月18日 [査読無し][通常論文]
  
• カゴメ格子磁性体BaCu₃V₂O₈(OH)₂のサブミリ波ESR III

  ZHANG W, 大久保晋, 友尾水樹, 櫻井敬博, 太田仁, 岡本佳比古, 吉田紘行, 広井善二 日本物理学会講演概要集 65 (2) 443 -443 2010年08月18日 [査読無し][通常論文]
  
• Cu₃V₂O₇(OH)₂・2H₂O(volborthite)における2種類のスピン状態の共存

  吉田誠, 瀧川仁, 吉田紘行, 岡本佳比古, 広井善二 日本物理学会講演概要集 65 (2) 386 -386 2010年08月18日 [査読無し][通常論文]
  
• Sr₂Ir_1-xRh_xO₄におけるスピン・軌道相互作用と磁気相関

  磯部雅朗, 吉田紘行, 室町英治, 入澤明典 日本物理学会講演概要集 65 (2) 576 -576 2010年08月18日 [査読無し][通常論文]
  
• Cu₃V₂O₇(OH)₂・2H₂O(volborthite)の強磁場磁気相図

  吉田誠, 瀧川仁, KRAMER S, MUKHOPADHYAY S, HORVATIC M, BERTHIER C, 吉田紘行, 岡本佳比古, 広井善二 日本物理学会講演概要集 65 (2) 387 2010年08月18日 [査読無し][通常論文]
  
• 20aPS-112 Sr_2Ir_<1-x>Rh_xO_4(x=0〜1)における金属絶縁体転移(20aPS 領域8ポスターセッション(低温I(遷移金属化合物,炭化・硼化物など)),領域8(強相関系:高温超伝導,強相関f電子系など))

  吉田 紘行, 磯部 雅朗, 室町 英治 日本物理学会講演概要集 65 (1) 546 -546 2010年03月01日
• 一次元系コバルト酸化物(Ca_1-xNa_x)Co₂O₄の輸送特性

  磯部雅朗, 吉田紘行, 橘信, 川嶋哲也, 新井正男, 室町英治, 入澤明典 日本物理学会講演概要集 65 (1) 648 -648 2010年03月01日 [査読無し][通常論文]
  
• 2次元三角格子Ag₂NiO₂,Ag₂MnO₂の共鳴光電子分光

  江口律子, 吉田紘行, 岡本佳比古, CHAINANI Ashish, 松波雅治, 石田行章, 大浦正樹, 仙波泰徳, 大橋治彦, 辛埴, 広井善二 日本物理学会講演概要集 65 (1) 801 -801 2010年03月01日 [査読無し][通常論文]
  
• スピン1/2カゴメ格子反強磁性体の銅鉱物の強磁場磁化過程

  岡本佳比古, 徳永将史, 吉田紘行, 広井善二 日本物理学会講演概要集 65 (1) 473 -473 2010年03月01日 [査読無し][通常論文]
  
• Sr₂Ir_1-xRh_xO₄(x=0~1)における金属絶縁体転移

  吉田紘行, 磯部雅朗, 室町英治 日本物理学会講演概要集 65 (1) 546 2010年03月01日 [査読無し][通常論文]
  
• S=1/2カゴメ格子反強磁性体の強磁場ESRによる研究

  ZHANG W, 大久保晋, 太田仁, 藤澤真士, 櫻井敬博, 岡本佳比古, 広井善二, 吉田紘行 日本物理学会講演概要集 65 (1) 473 -473 2010年03月01日 [査読無し][通常論文]
  
• カゴメ格子磁性体BaCu₃V₂O₈(OH)₂のテラヘルツ光ESR

  張衛民, 大久保晋, 友尾水樹, 櫻井敬博, 太田仁, 岡本佳比古, 吉田紘行, 広井善二 日本赤外線学会研究発表会資料 2010 48 -49 2010年 [査読無し][通常論文]
  
• カゴメ格子反強磁性体の多周波数ESR測定によるスピンフラストレーションとスピン液体の研究

  大久保晋, ZHANG W, 友尾水樹, 近藤健太, 藤澤真士, 櫻井敬博, 太田仁, 古川貢, 中村敏和, 木俣基, 宇治進也, 竹端寛治, 今中康貴, 高増正, 菊池彦光, 岡本佳比古, 吉田紘行, 廣井善二 電子スピンサイエンス学会年会講演要旨集 48th 132 -133 2009年11月10日 [査読無し][通常論文]
  
• S=1/2カゴメ格子反強磁性体Cu₃V₂O₇(OH)₂・2H₂Oの低周波ESR測定

  近藤健太, 友尾水樹, ZHANG W, 櫻井敬博, 藤澤真士, 大久保晋, 太田仁, 古川貢, 中村敏和, 木俣基, 竹端寛治, 今中康貴, 高増正, 宇治進也, 吉田紘行, 岡本佳比古, 廣井善二 電子スピンサイエンス学会年会講演要旨集 48th 128 -129 2009年11月10日 [査読無し][通常論文]
  
• カゴメ格子磁性体BaCu₃V₂O₈(OH)₂のサブミリ波ESR

  ZHANG W, 大久保晋, 太田仁, 藤澤真士, 櫻井敬博, 岡本佳比古, 吉田紘行, 広井善二 電子スピンサイエンス学会年会講演要旨集 48th 144 -145 2009年11月10日 [査読無し][通常論文]
  
• 25aRE-1 カゴメ格子上のスピン液体(領域3,領域8,領域11合同シンポジウム:フラストレーションとスピン液体,領域3,磁性,磁気共鳴)

  岡本 佳比古, 吉田 紘行, 広井 善二 日本物理学会講演概要集 64 (2) 322 -322 2009年08月18日
• 25pRE-5 S=1/2擬カゴメ格子磁性体volborthiteおよびvesignieiteのNMR(フラストレーション系・スピングラス(カゴメ格子・スピングラス),領域3,磁性,磁気共鳴)

  吉田 誠, 瀧川 仁, 吉田 紘行, 岡本 佳比古, 広井 善二 日本物理学会講演概要集 64 (2) 336 -336 2009年08月18日
• カゴメ格子上のスピン液体

  岡本佳比古, 吉田紘行, 広井善二 日本物理学会講演概要集 64 (2) 159 2009年08月18日 [査読無し][通常論文]
  
• スピン1/2カゴメ格子反強磁性体BaCu₃V₂O₈(OH)₂の磁性 II

  岡本佳比古, 徳永将史, 吉田紘行, 広井善二 日本物理学会講演概要集 64 (2) 386 -386 2009年08月18日 [査読無し][通常論文]
  
• カゴメ格子磁性体BaCu₃V₂O₈(OH)₂のサブミリ波ESR II

  ZHANG W, 大久保晋, 太田仁, 藤澤真士, 櫻井敬博, 岡本佳比古, 吉田紘行, 広井善二 日本物理学会講演概要集 64 (2) 336 -336 2009年08月18日 [査読無し][通常論文]
  
• S=1/2カゴメ格子反強磁性体の低周波ESR測定

  近藤健太, 友尾水樹, ZHANG W, 櫻井敬博, 藤澤真士, 大久保晋, 太田仁, 吉田紘行, 岡本佳比古, 廣井善二 日本物理学会講演概要集 64 (2) 398 -398 2009年08月18日 [査読無し][通常論文]
  
• カゴメ格子磁性体Cu₃V₂O₇(OH)₂・2H₂Oのサブミリ波ESR II

  近藤健太, ZHANG W, 大久保晋, 太田仁, 藤澤真士, 櫻井敬博, 古川貢, 中村敏和, 吉田紘行, 廣井善二 日本物理学会講演概要集 64 (1) 493 -493 2009年03月03日 [査読無し][通常論文]
  
• S=1/2擬カゴメ格子反強磁性体Cu₃V₂O₇(OH)₂・2H₂Oの磁化ステップ

  吉田紘行, 岡本佳比古, 徳永将史, 松尾晶, 鳴海康雄, 金道浩一, 田山孝, 榊原俊郎, 吉田誠, 瀧川仁, 広井善二 日本物理学会講演概要集 64 (1) 493 -493 2009年03月03日 [査読無し][通常論文]
  
• カゴメ格子磁性体BaCu₃V₂O₈(OH)₂のサブミリ波ESR

  ZHANG W, 大久保晋, 太田仁, 藤澤真士, 櫻井敬博, 岡本佳比古, 吉田紘行, 広井善二 日本物理学会講演概要集 64 (1) 494 -494 2009年03月03日 [査読無し][通常論文]
  
• S=1/2擬カゴメ格子磁性体Cu₃V₂O₇(OH)₂・2H₂OのNMR II

  吉田誠, 瀧川仁, 吉田紘行, 岡本佳比古, 広井善二 日本物理学会講演概要集 64 (1) 493 2009年03月03日 [査読無し][通常論文]
  
• スピン1/2カゴメ格子反強磁性体BaCu₃V₂O₈(OH)₂の磁性

  岡本佳比古, 吉田紘行, 広井善二 日本物理学会講演概要集 64 (1) 493 -493 2009年03月03日 [査読無し][通常論文]
  
• 2次元3角格子系Ag₂MnO₂の中性子回折

  蒲沢和也, 野崎洋, 杉山純, 吉田紘行, 廣井善二, MANSSON Martin, ROESSLI Bertrand, FISCHER Henry, HANSEN Thomas C 日本物理学会講演概要集 64 (1) 495 -495 2009年03月03日 [査読無し][通常論文]
  
• 22aQH-11 S=1/2擬カゴメ格子磁性体Cu_3V_2O_7(OH)_2・2H_2OのNMR(22aQH フラストレーション系(遷移金属酸化物・化合物),領域3(磁性,磁気共鳴))

  吉田 誠, 瀧川 仁, 吉田 紘行, 岡本 佳比古, 広井 善二 日本物理学会講演概要集 63 (2) 421 -421 2008年08月25日
• Ag₂MnO₂における電子比熱係数γの磁場依存性

  吉田紘行, 江口律子, 辛埴, 岡本佳比古, 山浦淳一, 広井善二 日本物理学会講演概要集 63 (2) 461 -461 2008年08月25日 [査読無し][通常論文]
  
• S=1/2疑カゴメ格子磁性体Cu₃V₂O₇(OH)₂・2H₂Oの基底状態における磁場誘起相転移

  吉田紘行, 岡本佳比古, 徳永将史, 松尾晶, 鳴海康雄, 金道浩一, 田山孝, 榊原俊郎, 広井善二 日本物理学会講演概要集 63 (2) 420 -420 2008年08月25日 [査読無し][通常論文]
  
• S=1/2擬カゴメ格子磁性体Cu₃V₂O₇(OH)₂・2H₂OのNMR

  吉田誠, 瀧川仁, 吉田紘行, 岡本佳比古, 広井善二 日本物理学会講演概要集 63 (2) 421 2008年08月25日 [査読無し][通常論文]
  
• カゴメ格子磁性体Cu₃V₂O₇(OH)₂・2H₂Oのサブミリ波ESR

  ZHANG W, 大久保晋, 太田仁, 藤澤真士, 櫻井敬博, 吉田紘行, 廣井善二 日本物理学会講演概要集 63 (2) 420 -420 2008年08月25日 [査読無し][通常論文]
  
• μSR測定によるAg₂MnO₂の磁気秩序状態

  野崎洋, 池戸豊, 向和彦, 杉山純, 吉田紘行, 広井善二, RUSSO Peter L, ANDREICA Daniel, AMATO Alex 日本物理学会講演概要集 63 (1) 642 -642 2008年02月29日 [査読無し][通常論文]
  
• S=1/2擬カゴメ格子磁性体Cu₃V₂O₇(OH)₂・2H₂Oの磁性

  吉田紘行, 岡本佳比古, 徳永将史, 広井善二 日本物理学会講演概要集 63 (1) 450 -450 2008年02月29日 [査読無し][通常論文]
  
• 2次元三角格子反強磁体Ag₂MnO₂におけるスピンカイラリティ転移の可能性

  吉田紘行, 岡本佳比古, JANSEN Martin, 廣井善二 日本物理学会講演概要集 63 (1) 459 -459 2008年02月29日 [査読無し][通常論文]
  
• Cu₃V₂O₇(OH)₂・2H₂OのテラヘルツESR

  張衛民, 大久保晋, 太田仁, 藤澤真士, 櫻井敬博, 吉田紘行, 廣井善二 日本赤外線学会研究発表会資料 2008 72 -73 2008年 [査読無し][通常論文]
  
• 幾何学的フラストレーションを有するMn化合物の磁化と比熱

  吉田紘行, 岡本佳比古, OBERNDORFER Christian, JANSEN Martin, 広井善二 日本物理学会講演概要集 62 (2) 537 -537 2007年08月21日 [査読無し][通常論文]
  
• 19aPS-102 銀を含む化合物Ag_2NiO_2の低温構造解析と新規銀化合物の探索 2(19aPS 領域8ポスターセッション(低温),領域8(強相関系:高温超伝導,強相関f電子系など))

  吉田 紘行, 村岡 祐治, 広井 善二, 垣内 徹, 澤 博, Oberndorfer Christian, Jansen M. 日本物理学会講演概要集 62 (1) 580 -580 2007年02月28日
• 19aPS-100 中性子回折およびμSR測定によるAg_2NiO_2の結晶構造と磁性(19aPS 領域8ポスターセッション(低温),領域8(強相関系:高温超伝導,強相関f電子系など))

  野崎 洋, 池戸 豊, 向 和彦, 杉山 純, 吉田 紘行, 広井 善二, Russo P. L., Ansaldo J., Brewer J. H., Janoschekc M., Roessli B., Keller L., Pomjakushin V. 日本物理学会講演概要集 62 (1) 579 -579 2007年02月28日
• 中性子回折による2次元3角格子系Ag₂NiO₂の結晶構造および磁気構造解析

  野崎洋, 杉山純, 吉田紘行, 広井善二, JANOSCHEK M, ROESSLI B, KELLER L, POMJAKSHIN V 日本中性子科学会年会講演概要集 7th 56 2007年 [査読無し][通常論文]
  
• 24aPS-62 銀を含む化合物Ag_2NiO_2の低温構造解析と新規銀化合物の探索(24aPS 領域8ポスターセッション(低温),領域8(強相関系:高温超伝導,強相関f電子系など))

  吉田 紘行, 村岡 祐治, 広井 善二, Sorgel Timo, Jansen Martin, 垣内 徹, 澤 博 日本物理学会講演概要集 61 (2) 454 -454 2006年08月18日
• 24aPS-58 ニッケル酸化物のμSR:Ag_2NiO_2多結晶(24aPS 領域8ポスターセッション(低温),領域8(強相関系:高温超伝導,強相関f電子系など))

  杉山 純, 池戸 豊, 向 和彦, 吉田 紘行, 広井 善二, Brewer J.H., Ansaldo E.J., Morris G.D., Chow K.H. 日本物理学会講演概要集 61 (2) 453 -453 2006年08月18日
• 27aUE-6 スピン1/2三角格子反強磁性体Ag_2NiO_2の物性及び不純物効果(27aUE 軌道秩序,領域8(強相関系:高温超伝導,強相関f電子系など))

  吉田 紘行, 村岡 祐治, 広井 善二, Soegel Timo, Jansen Martin 日本物理学会講演概要集 61 (1) 516 -516 2006年03月04日
• 20aPS-86 Ag_2NiO_2 : スピン1/2三角格子の磁性と伝導(領域8ポスターセッション(低温),領域8(強相関系 : 高温超伝導,強相関f電子系など))

  吉田 紘行, 村岡 祐治, 広井 善二, Soegel Timo, Jansen Martin 日本物理学会講演概要集 60 (2) 446 -446 2005年08月19日

受賞

• 2021年12月 日本物理学会誌 JPSJ Editor’s Choice
   μSR Study of Kapellasite-type Quantum Kagome Antiferromagnet CaCu3(OH)6Cl2·0.6H2O 

  受賞者: H. K. Yoshida, H. Okabe, S. Takeshita, H. Luetkens, A. Koda, and R. Kadono
• 2020年03月 日本物理学会 第14回日本物理学会若手奨励賞
   

  受賞者: 吉田紘行
• 2019年11月 強磁場フォーラム 第一回強磁場フォーラムフロンティア奨励賞
   

  受賞者: 吉田紘行
• 2019年05月 日本物理学会 Highly CiteArticle 2018
   Unusual Magnetic State with Dual Magnetic Excitations in the Single Crystal of S = 1/2 Kagome Lattice Antiferromagnet CaCu3(OH)6Cl2・0.6H2O 

  受賞者: H. Yoshida, N. Noguchi, Y. Matsushita, Y. Ishii, Y. Ihara, M. Oda, H. Okabe, S. Yamashita, Y. Nakazawa, A. 32Takata, T. Kida, Y. Narumi, and M. Hagiwara
• 2019年05月 日本物理学会 Highly Cited Article 2018
   Spin Resonance in the New-Structure-Type Iron-Based Superconductor CaKFe4As4 

  受賞者: K. Iida;M. Ishikado;Y. Nagai;H. Yoshida;A.D. Christianson;N. Murai;K. Kawashima;Y. Yoshida;H. Eisaki;A. Iyo
• 2017年11月 Physical Review B Editor's Suggestion
   Spin dynamics in the high-field phases of volborthite 

  受賞者: M. Yoshida;K. Nawa;H. Ishikawa;M. Takigawa;M. Jeong;S. Krämer;M. Horvatić;C. Berthier;K. Matsui;T. Goto;S. Kimura;T. Sasaki;J. Yamaura;H. Yoshida;Y. Okamoto;Z. Hiroi
• 2010年08月 HFM2010 ベストポスター賞
   Magnetic properties of novel classical triangular antiferromagnets Ag₂MO₂ (M = Cr, Fe) 

  受賞者: 吉田紘行
• 2009年 日本物理学会誌 JPSJ Editor’s Choice
   Vesignieite BaCu3V2O8(OH)2 as a Candidate Spin-1/2 Kagome Antiferromagnet 

  受賞者: Y. Okamoto, H. Yoshida, Z. Hiroi

共同研究・競争的資金等の研究課題

• アシンメトリが彩る量子物質の可視化・設計・創出の研究総括

  日本学術振興会：科学研究費助成事業

  研究期間 : 2023年04月 -2028年03月 

  代表者 : 鬼丸 孝博, 大槻 純也, 田端 千紘, 柳澤 達也, 大原 繁男, 吉田 紘行, 網塚 浩, 井澤 公一, 小林 達生, 小林 夏野, 木俣 基
• アシンメトリ量子物質の開拓

  日本学術振興会：科学研究費助成事業

  研究期間 : 2023年04月 -2028年03月 

  代表者 : 吉田 紘行, 芳賀 芳範, 松平 和之, 石渡 晋太郎, 小手川 恒
• ブリージング異方性の制御によるカゴメ反強磁性体の異常磁気物性の開拓

  日本学術振興会：科学研究費助成事業 基盤研究(B)

  研究期間 : 2021年04月 -2024年03月 

  代表者 : 吉田 紘行

   

  本研究課題は1/9磁化プラトーを示す古典カゴメ反強磁性体Li2Cr3SbO8においてブリージング異方性および量子性を摂動パラメータとして制御し、それらが磁気状態にどのような影響を与えるのかを明らかにし、カゴメ反強磁性体研究の新たなフロンティアの開拓を目指すものである。2021年度は、主に以下に記す2つの項目について研究を進め、具体的な成果を得る事に成功した。 1. 化学修飾および物理的圧力の印加によるブリージング異方性の制御を通して、1/9プラトーの安定性の評価と未知の量子相転移の探索を目指して研究を行なった。様々な修飾法を用いてLiサイトとSbサイトを化学置換することによるブリージング異方性の制御を試みたが、現段階で置換試料を得ることはできなかった。一方、物理圧力によるブリージング性の制御を並行して検討しており、圧力セルを用いた高圧下磁化測定の予備実験を進めることができた。 2. 1/9プラトーを含めた磁気状態に対する異方性の評価や、より本質的な磁性の解明を目指してLi2Cr3SbO8の単結晶育成に取り組んだ。本年度の研究の重要な成果として、Li2Cr3SbO8の単結晶を初めて育成することに成功した。最大で100μmとまだまだ結晶サイズは小さく課題は多いが、現在試みている結晶育成手法が概ね正しいことが分かった。次年度の研究によって、さらに大型の単結晶育成に取り組み、研究期間内での単結晶を用いた物性評価の完成に目処をつけたい。
  研究体制としては、粉末X線回折装置、誘電率測定のためのLCRメーター、温度コントローラーなどを導入し、試料評価および物性評価を進める態勢を構築した。次年度以降、ブリージングカゴメネットワークの局所反転対称性の破れに起因した磁気誘電特性の探索なども円滑に行うことが可能である。
• 小型汎用パルス強磁場を用いた先端測定による強磁場物性開拓

  日本学術振興会：科学研究費助成事業 基盤研究(B)

  研究期間 : 2019年04月 -2023年03月 

  代表者 : 井原 慶彦, 柳澤 達也, 松井 一樹, 吉田 紘行, 福岡 脩平, 小濱 芳允

   

  研究初年度となる2019年度は、本研究計画の主要装置となる小型パルス磁場発生装置の電源のエネルギーをを既存の10kJから30kJへと拡充し、更新した電源を用いてこれまでのところ20テスラ超までの磁場発生に成功した。これは、小規模の研究室における発生磁場としては最強レベルであり、ここまでの強磁場をコンパクトな磁場発生装置で勘弁に発生できることを実証できたことはすでに非常に意義がある。また、マグネットの強度を改善することで予定していた30テスラを超える磁場発生が可能であることが分かった。実際のマグネット改造は2年度への課題とした。 測定系では、まず超音波測定装置を立ち上げ、重い電子系物質において2 K以下までの超音波測定を可能にした。今回立ち上げた装置を用いて、量子振動の観測に成功し、実際の物性研究を行うに十分な測定精度を持つことが確認できた。特に、今回は高速オシロスコープを取り入れたデジタル分光方式を採用し、新しい測定原理に基づく超音波測定を実施できるようになったことは意義が深い。この方式は、パルス磁場中測定だけでなく、定常磁場中にも応用でき、測定難易度を下げることが期待される。 次に、核磁気共鳴分光装置に関しては、周波数の高速変調技術を確立し、5ミリ秒という短いパルス磁場発生時間中に非常に広帯域の周波数スペクトルの観測に成功した。この技術を用いて、20テスラまでのスペクトル測定はもとより、東京大学物性研究所における共同利用実験では53テスラまでのNMRスペクトル測定に成功し、その実用性が実証済みである。 最後に、3つ目のプローブとなる熱測定は、東京大学物性研究所においてすでに稼働しているパルス磁場中熱測定システムを用いた実験を行い、測定技術の移植を行っている。2019年度は測定に必要な装置群およびプローブの準備を行い、2020年度の立ち上げに備えた。
• 量子スピンカゴメ格子反強磁性体におけるスピン液体の実現とトポロジカル秩序の探索

  日本学術振興会：科学研究補助金（基盤研究(C)）

  研究期間 : 2018年04月 -2021年03月 

  代表者 : 吉田紘行
• 実空間と運動量空間の双方から見た銅酸化物高温超伝導と擬ギャップに対する不純物効果

  日本学術振興会：科学研究費補助金(基盤研究(C))

  研究期間 : 2015年04月 -2018年03月 

  代表者 : 小田研
• 遷移金属化合物における新電子物性開拓

  北海道大学：北海道大学総長室事業推進経費による研究支援事業「Fusion-H」

  研究期間 : 2015年04月 -2016年03月 

  代表者 : 吉田紘行
• S = 1/2カゴメ格子反強磁性体の特異な量子スピン液体状態の解明

  日本学術振興会：科学研究費補助金(若手研究(B))

  研究期間 : 2015年 -2016年 

  代表者 : 吉田 紘行

   

  Ca-Kapellasite, CaCu3(OH)6Cl2・0.6H2Oは格子歪みやイオンサイト乱れのないS = 1/2カゴメ格子反強磁性体のモデル物質であり、理論的な先行研究により量子スピン液体状態が実現する舞台になると予想されている。本研究では、Ca-Kapellasiteにおいて量子スピン液体状態の実現とその性質解明を目指して、単結晶育成、物性測定を行った。その結果、通常の長距離秩序とは異なる磁気基底状態が実現し、比熱の温度比例項に示唆されるギャップレスの特異な磁気励起が存在する事を見出した。
• フラストレーションの解放による新しい高温超伝導の実現

  北海道大学：北海道大学総長室事業推進経費「若手研究者自立支援A」

  研究期間 : 2014年04月 -2015年03月 

  代表者 : 吉田紘行
• フラストレート磁性体における新奇基底状態の解明－スピン液体と磁化ステップ現象－

  日本学術振興会：特別研究員奨励費(PD)

  研究期間 : 2010年04月 -2013年03月 

  代表者 : 吉田紘行
• スピン1/2三角格子を有する銀ニッケル酸化物の磁性と伝導

  日本学術振興会：特別研究員奨励費(DC2)

  研究期間 : 2007年04月 -2009年03月 

  代表者 : 吉田紘行

教育活動情報

主要な担当授業

大学運営

委員歴

• 2022年04月 - 現在   日本物理学会北海道支部 支部長
• 2018年09月 - 現在   物性グループ / 物性委員会   事務局員
• 2014年04月 - 現在   日本物理学会北海道支部   庶務
• 2017年10月 - 2018年09月   日本物理学会領域３   運営委員（議事進行）