出版者・発行元：Physical Review B  

We describe the existence of local distortion discovered in the synchrotron x-ray single-crystal structure analysis of layered ditelluride 1T-MTe2 (M=V, Nb, Ta). In 1T-TaTe2, the double zigzag chain structure of Ta is deformed at about 170 K, and heptamer molecules are formed periodically at low temperatures. We found that some of the Ta atoms that compose the double zigzag chain structure appearing at high temperatures are locally displaced, resulting in local dimerization. This tendency weakens when Ta is replaced by V or Nb. Our results indicate that the local distortion persistently survives in these ditellurides, where the electronic degrees of freedom, including orbitals, are weakened. We further discuss the origin of local distortion in these ditellurides, which is different from many usual material systems where molecular formation occurs at low temperatures.

DOI： 10.1103/PhysRevB.107.245113

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掲載種別：研究論文（学術雑誌）   出版者・発行元：Journal of the Physical Society of Japan  

We have investigated the temporal evolution and fluence dependence of band structure in Ta2Ni0.9Co0.1Se5 by means of time- and angle-resolved photoemission spectroscopy (tr-ARPES). With the fluence of 3.00 mJ cm−2 and the delay time of 170 fs, the conduction band crossing the Fermi level (EF) and the valence band reaching EF are observed indicating the photoinduced semimetal phase. However, at the delay time of 70 fs, the valence band top does not reach EF creating a partial gap or a pseudogap, and the transition from the excitonic insulator state to the semimetal state is not completed. The conduction band crossing EF is observed even with the shorter delay time (down to 50–70 fs) and=or the lower fluence (down to 0.32 mJ cm−2). On the other hand, the valence band top stays well below EF up to the fluence of 1.39 mJ cm−2 even at the delay time of 160–170 fs. The different optical responses of the valence and conduction bands suggest a vital role of the lattice fluctuations pointed out by Nakano et al. [Phys. Rev. B 98, 045139 (2018)] on the residual pseudogap at 70 fs after the photoexcitation.

DOI： 10.7566/JPSJ.92.064706

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掲載種別：研究論文（学術雑誌）   出版者・発行元：Acta Materialia  

Light environment drastically alters the plasticity of zinc sulfide (ZnS) single crystals: they exhibit ductility in darkness while brittleness in lights. This study investigated their microscopic deformation modes of the light-environment-dependent plasticity, by using synchrotron X-ray diffraction (XRD), transmission electron microscopy (TEM) and scanning TEM (STEM) measurements. The XRD analyses disclosed that the ZnS crystals originally have two domains with almost the same volume fraction with a twin relationship and plastically deform in darkness, accompanying changes in the domain volume ratio (namely extinction of twins). It was also observed that the domain volume ratios become constant to be 0.2 at more than 10% plastic strains. The STEM analyses indicated that the deformation mode in darkness switches at around 10% plastic strain from slip deformation by glide of isolated partial dislocations to by simultaneous glide of paired partials inside the major domains. Although ZnS single crystals exhibited only a few percent of plastic strains in lights, localized glide of isolated partials and the resultant changes in domain volume ratios similar to in darkness were confirmed. That is, the deformation modes of ZnS at the initial stage were similar regardless of light environments although the macroscopic deformation behaviors were quite different.

DOI： 10.1016/j.actamat.2023.118738

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掲載種別：研究論文（学術雑誌）   出版者・発行元：Journal of the Physical Society of Japan  

The photoinduced semimetal phase of Ta2Ni1−xCoxSe5 (x = 0.0 and 0.1) is studied by time-resolved angle-resolved photoemission spectroscopy. The observed band dispersions roughly agree with the generalized gradient approximation (GGA) calculation which fails to reproduce the band gap at the ambient condition. This suggests that the electron–hole interaction, which is not exactly included in GGA, is screened out by the photoexcited carriers. There is no indication of pseudogap. The conduction and valence bands provide quasi one-dimensional Fermi surfaces with similar momentum positions suggesting a quasi one-dimensional line-node semimetal.

DOI： 10.7566/JPSJ.92.023703

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掲載種別：研究論文（学術雑誌）   出版者・発行元：Physical Review B  

The layered chalcogenide Ta2NiSe5 has recently attracted much interest as a strong candidate for a long-sought excitonic insulator (EI). Since the physical properties of an EI are expected to depend sensitively on the external pressure (P), it is important to clarify the P evolution of a microscopic electronic state in Ta2NiSe5. Here we report the optical conductivity [σ(ω)] of Ta2NiSe5 measured at high P to 10 GPa and at low temperatures to 8 K. With cooling at P=0, σ(ω) develops an energy gap of about 0.17 eV and a pronounced excitonic peak at 0.38 eV as reported previously. With increasing P, the energy gap becomes narrower and the excitonic peak is diminished. Above a structural transition at Ps≃3 GPa, the energy gap becomes partially filled, indicating that Ta2NiSe5 is a semimetal after the EI state is suppressed by P. At higher P, σ(ω) exhibits metallic characteristics with no energy gap. The detailed P evolution of the energy gap and σ(ω) is presented, and discussed mainly in terms of a weakening of excitonic correlation with P.

DOI： 10.1103/PhysRevB.107.045141

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その他リンク： http://harvest.aps.org/v2/journals/articles/10.1103/PhysRevB.107.045141/fulltext

出版者・発行元：Physical Review B  

Vanadium atoms in layered LiVO2 form in-plane periodic vanadium trimers at low temperatures, but the trimers appear randomly in the stacking direction because there are many trimer configurations with comparable lattice energy. We detailed an original modeling scheme to represent glassy states with a completely disordered trimer configuration in the stacking structure. Through pair distribution function analysis using this model, we show that the synthesis method can yield two types of low-temperature stacking structures: a completely disordered stacking structure and a short-range order in the stacking structure. The phase-transition temperature of the former sample is about 15 K lower than that of the latter. We discuss that this is due to the strong trimer frustration that appears in the sample without short-range order, which suppresses the phase-transition temperature, similar to the frustration effect in conventional spin systems.

DOI： 10.1103/PhysRevB.107.L020101

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出版者・発行元：Nature Physics  

Crystal structures with degenerate electronic orbitals are unstable towards lattice distortions that lift the degeneracy. Although these Jahn–Teller distortions have profound effects on magnetism, they are typically unaffected by the onset of magnetic ordering because of a separation in energy scales. Here we show the contrary case in Pr2Zr2O7, where orbital degeneracy remains down to the millikelvin range due to an interplay between spins and orbitals. Pr2Zr2O7 is a multipolar spin ice with strongly localized 4f electrons in an even-number configuration, giving rise to a non-Kramers doublet that carries transverse quadrupolar and longitudinal dipolar moments. Our study of ultrapure single crystals of Pr2Zr2O7 finds comprehensive evidence for enhanced spin–orbital quantum dynamics of the non-Kramers doublet. This dynamical Jahn–Teller effect is encapsulated by the liquid–gas metamagnetic transition that is characteristic of spin ice being accompanied by strong lattice softening. This behaviour suggests that a spin–orbital liquid state forms on the pyrochlore lattice at low temperatures and low magnetic fields.

DOI： 10.1038/s41567-022-01816-4

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記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：Materials Advances  

Orbital degrees of freedom appear in partially filled degenerate orbitals and are responsible for a variety of physical properties. Although many methods for directly observing orbital states in ordered states have been proposed, it is difficult to determine degenerate orbital states directly. We found that high-precision diffraction data obtained by synchrotron radiation X-rays can be used to observe only the valence electron density distribution with minimal analytical bias. The results obtained using this method clearly showed the anisotropy of the partially filled degenerate 3d orbital states in spinel vanadium oxide FeV2O4. The 3d orbital quantum state was successfully determined from this anisotropy.

DOI： 10.1039/d1ma01113h

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記述言語：日本語   出版者・発行元：Journal of the Physical Society of Japan  

An excitonic insulator, in which an optical gap is formed by exciton condensation, is expected to exhibit large photoresponses. Here, we report the results of femtosecond reflection spectroscopy covering a wide infrared region on a typical excitonic insulator, Ta2NiSe5, which gives direct information not only about a change of excitonic gap but also a metallization. With a weak excitation, the excitonic gap decreases due to the weakening of excitonic effect by photocarriers. With a strong excitation, a Drude-like high-reflection band appears, showing an excitonic-insulator-to-metal transition. Analyses of spectral and temporal changes of reflectivity revealed that the metallization is accompanied by large structural changes. This demonstrates an important role of electron–lattice interaction on the stabilization of excitonic phase.

DOI： 10.7566/JPSJ.91.023701

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記述言語：日本語   掲載種別：研究論文（学術雑誌）   出版者・発行元：Physical Review B  

We report on the charge-ordered structure of LiRh2O4 arising below the metal-insulator transition at 170 K. Structural studies using synchrotron x rays have revealed that the charge-ordered states of Rh3+ and Rh4+ with dimerization are realized in the low-temperature phase below 170 K. Although the low-temperature ground state resembles that of CuIr2S4, a charge-ordering pattern satisfying the Anderson condition is realized in LiRh2O4. Based on structural information such as the short-range order of dimers appearing above the transition temperature and the weakening of the correlation between rhodium one-dimensional chains appearing in the crystal structure, we argue that the Coulomb interaction plays an important role in determining the charge-ordering patterns.

DOI： 10.1103/PhysRevB.105.L041103

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その他リンク： http://harvest.aps.org/v2/journals/articles/10.1103/PhysRevB.105.L041103/fulltext

記述言語：日本語   掲載種別：研究論文（学術雑誌）   出版者・発行元：Journal of the Physical Society of Japan  

The excitonic insulator Ta2NiSe5 experiences a first-order structural transition under pressure from rippled to flat layer-structure at Ps ~ 3 GPa, which drives the system from an almost zero-gap semiconductor to a semimetal. The pressure-induced semimetal, with lowering temperature, experiences a transition to another semimetal with a partial-gap of ~0.1-0.2 eV, accompanied with a monoclinic distortion analogous to that occurs at the excitonic transition below Ps. We argue that the partial-gap originates primarily from a symmetry-allowed hybridization of Ta-conduction and Nivalence bands due to the lattice distortion, indicative of the importance of electron-lattice coupling. The transition is suppressed with increasing pressure to Pc ~ 8 GPa. Superconductivity with a maximum Tsc ~ 1.2K emerges around Pc, likely mediated by strongly electron-coupled soft phonons. The electron-lattice coupling is as important ingredient as the excitonic instability in Ta2NiSe5.

DOI： 10.7566/JPSJ.90.074706

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記述言語：日本語   掲載種別：研究論文（学術雑誌）   出版者・発行元：Physical Review B  

Structural parameters in quasi-one-dimensional organic conductors (TMTTF)2X (X=NbF6, AsF6, PF6, and Br) are investigated by synchrotron X-ray diffraction. The temperature dependences of the crystal structures differ significantly between octahedral and monatomic anion systems, corresponding to the presence or absence of a charge-ordering transition. Changes in temperature and chemical pressure control the dimensionality of the lattice and the degree of dimerization. Furthermore, the antiferromagnetic and spin-Peierls ground states in this system depend on the spin frustration due to transfer integral paths between the one-dimensional chain molecules.

DOI： 10.1103/PhysRevB.103.184112

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記述言語：日本語   掲載種別：研究論文（学術雑誌）   出版者・発行元：Inorganic Chemistry  

An unusual valence one-dimensional (1D) molecular charge transfer salt (TMTTF)(NbOF4) [TMTTF = tetramethyltetrathiafulvalene] with infinite anion chains was prepared. To understand the crystal structure and electronic states of the (TMTTF)(NbOF4) salt, we performed synchrotron X-ray diffraction, electron spin resonance, and static magnetization measurements. There is only one independent TMTTF molecule in the unit cell of (TMTTF)(NbOF4). The TMTTF1+ cation radicals stack to form 1D columns. The effective charge of the TMTTF molecule in the crystal was estimated to be +1. The electric charge of TMTTF donors is compensated by the infinite anion chains [(NbOF4)-]∞. The magnetic susceptibility of (TMTTF)(NbOF4) is 4 × 10-4 emu/mol at room temperature and shows weak temperature dependence above 60 K. However, some deviation appears below 60 K. The temperature dependence of the spin susceptibility shows a noticeable enhancement below 60 K. Below 5 K, the magnetization curve as a function of the magnetic field deviates from the straight line and shows a saturation tendency. The experimental results can be reproduced well with the S = 2 spin system at 2 K. The detailed analysis of the crystal structure and anomalous low-temperature magnetic state magnetic properties of (TMTTF)(NbOF4) are discussed.

DOI： 10.1021/acs.inorgchem.1c00208

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PubMed

記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：Physical Review B  

Photoinduced phase transitions have been intensively studied owing to the potential capability to control a material of interest in the ultrafast manner, which can induce exotic phases unable to be attained at equilibrium. However, the key mechanisms are still under debate, and it is currently a central issue as to how the couplings between the electron, lattice, and spin degrees of freedom are evolving during photoinduced phase transitions. Here, we use a recently developed analysis method, which we call frequency-domain angle-resolved photoemission spectroscopy (FDARPES), and reveal mode- and band-selective electron-phonon couplings during the photoinduced insulator-to-metal transition for Ta2NiSe5. We find that the lattice modulation corresponding to the 2 THz phonon mode, where the Ta lattice is sheared along the a axis, is the most relevant for the emergence of photoinduced semimetallic state. Furthermore, we find that the semimetallic and semiconducting bands coexist in the transient state, and demonstrate that FDARPES spectra can selectively detect the phonon-specific couplings to the two coexistent band structures during the photoinduced phase transition by resolving them in the frequency domain.

DOI： 10.1103/PhysRevB.103.L121105

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掲載種別：研究論文（学術雑誌）   出版者・発行元：npj Quantum Materials  

Electronic instabilities in transition metal compounds often spontaneously form orbital molecules, which consist of orbital-coupled metal ions at low temperature. Recent local structural studies utilizing the pair distribution function revealed that preformed orbital molecules appear disordered even in the high-temperature paramagnetic phase. However, it is unclear whether preformed orbital molecules are dynamic or static. Here, we provide clear experimental evidence of the slow dynamics of disordered orbital molecules realized in the high-temperature paramagnetic phase of LiVS2, which exhibits vanadium trimerization upon cooling below 314 K. Unexpectedly, the preformed orbital molecules appear as a disordered zigzag chain that fluctuate in both time and space under electron irradiation. Our findings should advance studies on soft matter physics realized in an inorganic material due to disordered orbital molecules.

DOI： 10.1038/s41535-021-00313-w

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その他リンク： http://www.nature.com/articles/s41535-021-00313-w

記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：Physical Review B  

We investigated the precise crystal structures and electronic states of a quasi-two-dimensional molecular conductor α-(BETS)2I3 at ambient pressure. The electronic resistivity of this molecular solid shows metal-to-insulator (MI) crossover behavior at TMI=50K. Our x-ray diffraction and C13 nuclear magnetic resonance experiments revealed that α-(BETS)2I3 maintains the inversion symmetry below TMI. First-principles calculations found a pair of anisotropic Dirac cones at a general k point, with the degenerate contact points at the Fermi level. The origin of the insulating state in this system is a small energy gap of ∼2meV opened by the spin-orbit interaction. The Z2 topological invariants indicate that this system is a weak topological insulator. Our results suggest that α-(BETS)2I3 is a promising material for studying the bulk Dirac electron system in two dimensions.

DOI： 10.1103/PhysRevB.103.035135

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arXiv

その他リンク： http://arxiv.org/pdf/2006.08978v1

掲載種別：研究論文（学術雑誌）   出版者・発行元：The Crystallographic Society of Japan  

DOI： 10.5940/jcrsj.62.221

記述言語：日本語   掲載種別：研究論文（学術雑誌）   出版者・発行元：Journal of the Physical Society of Japan  

We report time-resolved angle-resolved photoemission study on Ta2Ni1−xCoxSe5 (x = 0.10) in which the excitonic insulator (EI) transition temperature is reduced by Co substitution for Ni. In the photoinduced phase, the conduction band is clearly observed and the energy gap between the conduction and valence bands is undetectably small within the energy resolution. Assuming that the energy gap is closed, the conduction band crosses or overlaps with the valence band near the Fermi level resembling a nodal semimetal.

DOI： 10.7566/JPSJ.89.124703

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記述言語：日本語   掲載種別：研究論文（学術雑誌）   出版者・発行元：Crystals  

The physical properties of molecular crystals are governed by the frontier orbitals of molecules. A molecular orbital, which is formed by superposing the atomic orbitals of constituent elements, has complicated degrees of freedom in the crystal because of the influence of electron correlation and crystal field. Therefore, in general, it is difficult to experimentally observe the whole picture of a frontier orbital. Here, we introduce a new method called “core differential Fourier synthesis” (CDFS) using synchrotron X-ray diffraction to observe the valence electron density in materials. By observing the valence electrons occupied in molecular orbitals, the orbital state can be directly determined in a real space. In this study, we applied the CDFS method to molecular materials such as diamond, C60 fullerene, (MV)I2, and (TMTTF)2X. Our results not only demonstrate the typical orbital states in some materials, but also provide a new method for studying intramolecular degrees of freedom.

DOI： 10.3390/cryst10110998

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記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：Physical Review Research  

The orbital degree of freedom of electrons greatly influences the physical properties of materials such as magnetic order and unconventional superconductivity. An orbital is a minimal unit of "shape,"and the orbital state can be unraveled by observing the spatial anisotropic distribution of electrons. However, it is difficult to experimentally extract the orbital information in a crystal because of various technical problems. Here, the Ti-3d orbital state in perovskite-type oxides RTiO3 (R=Y, Sm, and La) is directly determined by a core differential Fourier synthesis (CDFS) method using synchrotron X-ray diffraction. The valence electron-density distribution, including information on the anisotropy and the hybridization between atomic orbitals, can be extracted from the CDFS analysis. Our study not only demonstrates the relationship between the magnetic- A nd orbital-ordered states called the Kugel-Khomskii model, but also provides a nontrivial picture of the orbital state reconstructed by the orbital hybridization.

DOI： 10.1103/PhysRevResearch.2.033503

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記述言語：日本語   掲載種別：研究論文（学術雑誌）   出版者・発行元：Physical Review B  

In this study, we present a rutile-related material, LiMoO2, that becomes a cluster magnet and exhibits a spin singlet formation on a preformed molybdenum dimer upon cooling. Unlike ordinary cluster magnets, the atomic dyz orbital robustly survives despite the formation of molecular orbitals, thereby affecting the magnetic properties of the selected material. Such hybrid cluster magnets with the characters of molecular and atomic orbitals realize multiple independent spins on an isolated cluster, leading to an ideal platform to study the isolated spin dimers physics.

DOI： 10.1103/PhysRevB.102.081106

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その他リンク： http://harvest.aps.org/v2/journals/articles/10.1103/PhysRevB.102.081106/fulltext

記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：Nature Communications  

Since the discovery of the Verwey transition in magnetite, transition metal compounds with pyrochlore structures have been intensively studied as a platform for realizing remarkable electronic phase transitions. We report on a phase transition that preserves the cubic symmetry of the β-pyrochlore oxide CsW2O6, where each of W 5d electrons are confined in regular-triangle W3 trimers. This trimer formation represents the self-organization of 5d electrons, which can be resolved into a charge order satisfying the Anderson condition in a nontrivial way, orbital order caused by the distortion of WO6 octahedra, and the formation of a spin-singlet pair in a regular-triangle trimer. An electronic instability due to the unusual three-dimensional nesting of Fermi surfaces and the strong correlations of the 5d electrons characteristic of the pyrochlore oxides are both likely to play important roles in this charge-orbital-spin coupled phenomenon.

DOI： 10.1038/s41467-020-16873-7

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PubMed

記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：Physical Review B  

Cu+ ion behavior is one of the heavily discussed topics in physical and material fields because of its unclear behavior and high potential in materials application. To provide a breakthrough in this field, comprehensive research that connects the real space and the reciprocal lattice (momentum) space is effective. Here, we investigated the Cu+ ion behavior in two-dimensional layered system Cu0.33TiSe2, which shows the Cu+ disorder-order phase transition at 200 K. Inelastic x-ray scattering revealed a large change of the Cu+ ion dynamics at the phase transition. It is expected that the complex interactions are involved in the behavior of Cu+ ions intercalated in the negatively charged TiSe2 layers by charge transfer. However, Monte Carlo simulations using a simple combination of repulsive forces between Cu+ ions well reproduce the characteristic temperature dependence of the anisotropic diffuse scattering. These insights provide a unified understanding in controlling the intercalated system.

DOI： 10.1103/PhysRevB.101.094108

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DOI： 10.1088/1742-6596/1609/1/012001

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記述言語：日本語   掲載種別：研究論文（学術雑誌）   出版者・発行元：Physical Review B  

Ta2NiS5 is supposed to be a simple semiconductor in which excitonic instability of Ta2NiSe5 is suppressed due to its large band gap. However, the Ni 2p core-level photoemission of Ta2NiS5 exhibits a satellite indicating Ni 3d orbitals are mixed into its conduction band as expected in an excitonic insulator. The valence band does not show dispersion flattening and spectral sharpening which are fingerprints of an excitonic insulator. Instead, Ni 3p-3d resonant photoemission indicates Mottness of the Ni 3d electron in Ta2NiS5 with negative charge-transfer energy. The present results show that Ta2NiS5 can be viewed as a valence bond insulator with a band gap exceeding the exciton binding energy.

DOI： 10.1103/PhysRevB.100.245129

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記述言語：日本語   掲載種別：研究論文（学術雑誌）   出版者・発行元：Physical Review B  

Herein, we discuss the identification of vanadium trimers in layered LiVO2 and its sulfide analog of LiVS2 with two-dimensional triangular lattices. Our comprehensive structural studies using synchrotron X-ray-diffraction experiments clarified that vanadium trimers are randomly aligned along the c-axis direction in LiVO2, while the long-range ordering of vanadium trimers along the c-axis direction appears in LiVS2. Our results solve the long-standing issue of cluster patterns in LiVO2 and provide an experimental basis for identifying the mechanism of trimer formation.

DOI： 10.1103/PhysRevB.100.235120

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記述言語：日本語   出版者・発行元：Physical Review X  

The thermal conductivity κ of the quasi-2D organic spin-liquid candidate EtMe3Sb[Pd(dmit)2]2 (dmit-131) was measured at low temperatures, down to 0.07 K. We observe a vanishingly small residual linear term κ0/T, in κ/T vs T as T→0. This shows that the low-energy excitations responsible for the sizable residual linear term γ in the specific heat C, seen in C/T vs T as T→0, are localized. We conclude that there are no mobile gapless excitations in this spin-liquid candidate, in contrast with a prior study of dmit-131 that reported a large κ0/T value [Yamashita, Science 328, 1246 (2010)SCIEAS0036-807510.1126/science.1188200]. Our study shows that dmit-131 is in fact similar to κ-(BEDT-TTF)2Cu2(CN)3, another quasi-2D organic spin-liquid candidate where a vanishingly small κ0/T and a sizable γ are seen. We attribute heat conduction in these organic insulators without magnetic order to phonons undergoing strong spin-phonon scattering, as observed in several other spin-liquid materials.

DOI： 10.1103/PhysRevX.9.041051

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記述言語：日本語   掲載種別：研究論文（学術雑誌）   出版者・発行元：Journal of the Physical Society of Japan  

We have measured the dielectric constant and thermopower of single crystal samples of the excitonic insulator candidate Ta2NiSe5. The dielectric constant below 50 K shows relaxor-like relaxation, implying the existence of randomly distributed electric dipoles. We have evaluated the concentration of the dipoles to be 1019 cm−3 at 30 K, which gives a rough estimate of the exciton concentration in this compound. A large thermopower of 600 µV=K at 100 K suddenly drops toward zero down to 50 K, and this zero thermopower evidences the neutral particles flow against the applied temperature gradient. We have semi-quantitatively explained the above two anomalies in terms of spontaneously generated excitons at low temperatures where thermally excited holes are quenched.

DOI： 10.7566/JPSJ.88.113706

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記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：Inorganic Chemistry  

Anomalous successive structural transitions in layered 1T-CrSe2 with an unusual Cr4+ valency were investigated by synchrotron X-ray diffraction. 1T-CrSe2 exhibits dramatic structural changes in in-plane Cr-Cr and interlayer Se-Se distances, which originate from two interactions: (i) in-plane Cr-Cr interactions derived from Peierls-like trimerization instabilities on the orbitally assisted one-dimensional chains and (ii) interlayer Se-Se interactions through p-p hybridization. As a result, 1T-CrSe2 has the unexpected ground state of an antiferromagnetic metal with multiple Cr linear trimers with three-center-two-electron σ bonds. Interestingly, partial substitution of Se for S atoms in 1T-CrSe2 changes the ground state from an antiferromagnetic metal to an insulator without long-range magnetic ordering, which is due to the weakening of interlayer interactions between anions. The unique low-temperature structures and electronic states of this system are determined by the competition and cooperation of in-plane Cr-Cr and interlayer Se-Se interactions.

DOI： 10.1021/acs.inorgchem.9b00186

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PubMed

記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：Physical Review B  

We synthesized a kagome fluoride Cs2LiTi3F12 with S=1/2 spins, and studied magnetic properties of the compound. The temperature dependence of the magnetic susceptibility indicates that it has dominant antiferromagnetic interactions and that it has no magnetic order down to 2 K. We found two magnetization plateaus in its magnetization process approximately at 1/3 and 0.8 μB per Ti. The monoclinic crystal structure gives four inequivalent nearest-neighbor exchange interactions. Our density functional theory calculations suggest that three of them are antiferromagnetic and one of them is weakly ferromagnetic, resulting in a magnetic system composed of antiferromagnetically coupled linear chains and Δ chains. This explains the observed suppression of magnetic order. Numerical diagonalization gives a magnetization curve in good agreement with the experimental results.

DOI： 10.1103/PhysRevB.100.174401

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記述言語：日本語   掲載種別：研究論文（学術雑誌）   出版者・発行元：Dalton Transactions  

The Au(iii)-complex anions in a newly synthesised compound BPY[Au(dmit)2]2 (BPY = N,N-ethylene-2,2-bipyridinium, dmit = 1,3-dithiole-2-thione-4,5-dithiolate) reversibly exhibit a molecular distortion in the solid state under UV-radiation. The photoexcited state is maintained for a week at 298 K, during which time molecules relax to their original structures and energy is gradually released as heat without decomposition or light emission. Most Au atoms adopt square planar (SP) coordination geometries, but some anions have unusual non-planar (NP) coordination geometries that produce disorder at the Au sites. The total (Gibbs) energy of the system depends on the proportion of Au atoms of NP geometry, which is directly determined from the occupancy (Occ (%)) by X-ray diffractometry. Due to phase transition, Occ substantially changes at a critical temperature (TC) of ∼280 K without other structural changes; however it remains almost constant in each phase. In addition, due to UV-promoted charge-transfer transitions between BPY and Au(dmit)2, Occ can be controlled by UV irradiation (∼250-450 nm). The UV-excited states have unprecedentedly long relaxation times (t1/2 > 36 h at 298 K), which is attributed to the close connection between the degrees of freedom on charge, spin, and molecular structures.

DOI： 10.1039/c9dt02377a

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PubMed

記述言語：日本語   掲載種別：研究論文（学術雑誌）   出版者・発行元：Chemistry of Materials  

Li2SrNb2O7 (LSNO) crystallizes in a structure closely related to n = 2 Ruddlesden-Popper-type compounds, which are generally formed by intergrowth of two-dimensional perovskite-type blocks and rocksalt-type layers. The present study demonstrates the coexistence of spontaneous polarization and an anti-ferroelectric-like nonlinear response in LSNO at 80 K, suggesting weak ferroelectricity below the phase transition temperature of 217 K. A combination of first-principles calculations and single-crystal X-ray diffractions clarifies a polar P21cn structure for the ground state of LSNO, where an in-plane antiferroelectric displacement and an out-of-plane polar shift simultaneously take place. The present study offers a new perspective to design ferroelectric and antiferroelectric materials with Ruddlesden-Popper-type compounds.

DOI： 10.1021/acs.chemmater.9b02373

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記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：Physical Review B  

1T-TiSe2 has a semimetallic band structure at room temperature and undergoes phase transition to a triple-q charge-density wave (CDW) state with a commensurate superlattice structure (2a×2a×2c) below Tc≈200K at ambient pressure. This phase transition is caused by cooperative phenomena involving electron-phonon and electron-hole (excitonic) interactions, and cannot be described by a standard CDW framework. By Cu intercalation or the application of pressure, this phase-transition temperature is suppressed and superconductivity (SC) appears. However, it is not clear what kind of order parameters are affected by these two procedures. We investigated the crystal structure of CuxTiSe2 and pressurized 1T-TiSe2 around the SC state by synchrotron x-ray diffraction on single crystals. In the high-temperature phase, the variations of structural parameters for the case of Cu intercalation and application of pressure are considerably different. Moreover, the relationship between the critical points of the CDW phase transition and the SC dome are also different for the two cases. The excitonic interaction appears to play an important role in the P-T phase diagram of 1T-TiSe2, but not in the x-T phase diagram.

DOI： 10.1103/PhysRevB.99.104109

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出版者・発行元：American Journal of Pathology  

Localization of the abnormal and normal isoforms of prion proteins to detergent-resistant membrane microdomains, lipid rafts, is important for the conformational conversion. Lipid rafts are enriched in sialic acid–containing glycosphingolipids (namely, gangliosides). Alteration in the ganglioside composition of lipid rafts can affect the localization of lipid raft–associated proteins. To investigate the role of gangliosides in the pathogenesis of prion diseases, we performed intracerebral transmission study of a scrapie prion strain Chandler and a Gerstmann-Sträussler-Scheinker syndrome prion strain Fukuoka-1 using various knockout mouse strains ablated with ganglioside synthase gene (ie, GD2/GM2 synthase, GD3 synthase, or GM3 synthase). After challenge with the Chandler strain, GD2/GM2 synthase knockout mice showed 20% reduction of incubation time, reduced prion protein deposition in the brain with attenuated glial reactions, and reduced localization of prion proteins to lipid rafts. These results raise the possibility that the gangliosides may have an important role in prion disease pathogenesis by affecting the localization of prion proteins to lipid rafts.

DOI： 10.1016/j.ajpath.2018.11.009

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記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：Physical Review B  

The phase transition phenomenon in a semimetallic 1T-TiSe2 has attracted attention as an excitonic insulator. However, as the phase transition accompanying superlattice peaks has the q vector connecting the Fermi surfaces of the three-dimensional shape of hole and electron pockets, it also assumes the charge density wave (CDW) state owing to the electron-phonon interaction. To understand the electronic state at the low temperature, control of the chemical potential was attempted by electronic doping through Cu+ intercalation. Physical properties measurements and synchrotron x-ray diffraction experiments in CuxTiSe2 (x=0-0.35) were performed. The phase transition was determined to occur as a cooperative phenomenon between the honeycomb lattice type CDW corresponding to the nesting vector and the ordered state of the Cu+ ions between TiSe2 layers at a specific doping amount (x=1/3). The behavior of Cu+ ions in highly doped regions suggests the occurrence of a two-dimensional liquid-solid state transition based on the temperature dependence of the x-ray diffuse scattering.

DOI： 10.1103/PhysRevB.99.081111

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出版者・発行元：Journal of Physics Condensed Matter  

Structure with orbital degeneracy is unstable toward spontaneous distortion. Such orbital correlation usually has a much higher energy scale than spins, and therefore, magnetic transition takes place at a much lower temperature, almost independently from orbital ordering. However, when the energy scales of orbitals and spins meet, there is a possibility of spin-orbital entanglement that would stabilize novel ground state such as spin-orbital liquid and random singlet state. Here we review on such a novel spin-orbital magnetism found in the hexagonal perovskite oxide Ba3CuSb2O9, which hosts a self-organized honeycomblike short-range order of a strong Jahn-Teller ion Cu2+. Comprehensive structural and magnetic measurements have revealed that the system has neither magnetic nor Jahn-Teller transition down to the lowest temperatures, and Cu spins and orbitals retain the hexagonal symmetry and paramagnetic state. Various macroscopic and microscopic measurements all indicate that spins and orbitals remain fluctuating down to low temperatures without freezing, forming a spin-orbital entangled liquid state.

DOI： 10.1088/1361-648X/aae106

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PubMed

記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：Nature Communications  

Using light to manipulate materials into desired states is one of the goals in condensed matter physics, since light control can provide ultrafast and environmentally friendly photonics devices. However, it is generally difficult to realise a photo-induced phase which is not merely a higher entropy phase corresponding to a high-temperature phase at equilibrium. Here, we report realisation of photo-induced insulator-to-metal transitions in Ta2Ni(Se1−xSx)5 including the excitonic insulator phase using time- and angle-resolved photoemission spectroscopy. From the dynamic properties of the system, we determine that screening of excitonic correlations plays a key role in the timescale of the transition to the metallic phase, which supports the existence of an excitonic insulator phase at equilibrium. The non-equilibrium metallic state observed unexpectedly in the direct-gap excitonic insulator opens up a new avenue to optical band engineering in electron–hole coupled systems.

DOI： 10.1038/s41467-018-06801-1

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出版者・発行元：Optics Express  

We report novel white light-emitting diode (WLED) devices that improve emission color uniformity. The WLEDs consist of a violet chip and a mixed-phosphor layer of three phosphors previously developed by us. It is found that each phosphor does not reabsorb the luminescence from the other phosphors; consequently, the emission color of the WLEDs does not get affected by the mounted quantity of phosphors and/or the variation in chip emission wavelength. Furthermore, an encapsulated WLED with a hemispherical dome-shaped mixed-phosphor layer enables an area to be irradiated with uniform color, producing an excellent color rendering index and improved luminous flux because of the reduced inelastic scattering loss in the phosphor layer.

DOI： 10.1364/OE.26.024784

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PubMed

記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：Physical Review B  

© 2018 American Physical Society. We discuss herein the emergence of a large entropy change in metallic Li0.33VS2 derived from orbitally assisted loose σ bond formation. Comprehensive structural studies based on synchrotron x-ray and neutron diffraction analyses clarify the fabrication of ribbon chains at 375 K, consisting of multiple three-centered two-electron σ bonds based on the viewpoint of local chemical bonding. Although the metallic conductivity persists down to the lowest temperature measured, an exceptionally large entropy change as a metal, as much as ΔS=6.6Jmol-1K-1, appears at the transition. The emergence of a large entropy change in a metallic state may possibly lead to different functional materials, such as a heat-storage material with a rapid thermal response.

DOI： 10.1103/PhysRevB.98.081104

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記述言語：英語   出版者・発行元：Physical Review B  

© 2018 American Physical Society. Ta2NiSe5 is considered a promising excitonic insulator (EI) candidate, in which the EI state is due to Coulomb interaction between electrons and holes. In Ta2NiSe5, the role of phonons is significant since the EI transition is accompanied by an orthorhombic-to-monoclinic structural transition at Ts=328K. Our inelastic x-ray scattering measurements reveal that the transverse acoustic mode exhibits strong softening just above Ts. Furthermore, the transverse optical mode exhibits linewidth broadening caused by strong electron-optical-phonon coupling above Ts. Density functional theory calculations indicate that the coupled optical modes arise due to the vibration of Ta ions. Consequently, in the monoclinic phase, the coupled optical modes are "frozen" such that Ta and Se approach each other, forming atomic-displacement-type electric dipoles that are obviously different from a Peierls transition or Jahn-Teller distortion. The characteristic of electronic toroidal moment formation by the antiferroelectric arrangements of the electric dipoles forms the common feature between Ta2NiSe5 and 1T-TiSe2.

DOI： 10.1103/PhysRevB.98.045139

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記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：Physical Review B  

We have investigated the structural and magnetic properties of S=3/2Cr3+ Heisenberg-like kagome lattice antiferromagnets Cs2KCr3F12 and Cs2NaCr3F12 using single crystals. Each compound has a slightly distorted kagome lattice, although the space groups differ for the two compounds. The magnetic data suggest that each compound exhibits the formation of antiferromagnetic ordering with in-plane-spin canting approximately below 6 K. The in-plane coplanar structures are clearly different from disordered ground states of the isostructural Ti3+ compounds and out-of-plane coplanar structures of the V3+ compounds, which is mainly caused by the differences in the strength of quantum fluctuation and the strength of magnetic anisotropy for these three spin systems. In contrast, as well as the Ti3+ and V3+ compounds, the magnetization curves show 1/3-magnetization-plateaulike anomalies.

DOI： 10.1103/PhysRevB.97.224421

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記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：Physical Review Materials  

The physical properties of the mixed-valent iron oxide β-NaFe2O3 were investigated by means of synchrotron radiation x-ray diffraction, magnetization, electrical resistivity, differential scanning calorimetry, Na23 NMR, and Fe57Mössbauer measurements. This compound has double triangular layers consisting of almost perfect regular Fe4 tetrahedra, which suggests geometrical frustration. We found that this compound exhibits an electrostatically unstable double-stripe-type charge ordering, which is stabilized by the cooperative compression of Fe3+O6 octahedra, owing to a valence change and Fe2+O6 octahedra due to Jahn-Teller distortion. Our results indicate the importance of electron-phonon coupling for charge ordering in the region of strong charge frustration.

DOI： 10.1103/PhysRevMaterials.2.054402

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記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：IUCrJ  

The crystal structure of the excitonic insulator Ta2NiSe5 has been investigated under a range of pressures, as determined by the complementary analysis of both single-crystal and powder synchrotron X-ray diffraction measurements. The monoclinic ambient-pressure excitonic insulator phase II transforms upon warming or under a modest pressure to give the semiconducting C-centred orthorhombic phase I. At higher pressures (i.e. >3GPa), transformation to the primitive orthorhombic semimetal phase III occurs. This transformation from phase I to phase III is a pressure-induced first-order phase transition, which takes place through coherent sliding between weakly coupled layers. This structural phase transition is significantly influenced by Coulombic interactions in the geometric arrangement between interlayer Se ions. Furthermore, upon cooling, phase III transforms into the monoclinic phase IV, which is analogous to the excitonic insulator phase II. Finally, the excitonic interactions appear to be retained despite the observed layer sliding transition.

DOI： 10.1107/S2052252517018334

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記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：Journal of the Physical Society of Japan  

The distribution of d-orbital valence electrons in volborthite [Cu3V2O7(OH)212H2O] was investigated by charge density analysis of the multipole model refinement. Diffraction data were obtained by synchrotron radiation single-crystal X-ray diffraction experiments. Data reduction by detwinning of the multiple structural domains was performed using our developed software. In this study, using high-quality data, we demonstrated that the water molecules in volborthite can be located by the hydrogen bonding in cavities that consist of Kagome lattice layers of CuO4(OH)2 and pillars of V2O7. Final multipole refinements before and after the structural phase transition directly visualized the deformation electron density of the valence electrons. We successfully directly visualized the orbital flipping of the d-orbital dx2–y2, which is the highest level of 3d orbitals occupied by d9 electrons in volborthite. The developed techniques and software can be employed for investigations of structural properties of systems with multiple structural domains.

DOI： 10.7566/JPSJ.87.024601

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記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：Chemical Communications  

We report a K2CaPO4F:Eu2+ phosphor with a new crystal structure. This phosphor has a large Stokes shift and converts near-ultraviolet light to red luminescence without absorption of other visible light. The mechanism was elucidated by applying a constrained density functional theory to the solved crystal structure.

DOI： 10.1039/c7cc08202a

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PubMed

記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：Journal of the Physical Society of Japan  

We present structural studies of the spin-1/2 honeycomb-lattice antiferromagnet, Cu2(pymca)3(ClO4) (pymca: pyrimidine-2-carboxylate), using synchrotron X-ray diffraction experiments. Previous research reported that its crystal structure consists of a regular honeycomb lattice, which exhibits quantum spin-liquid behavior. However, due to its threefold Cu2+ site symmetry, this proposed crystal structure cannot describe Jahn–Teller distortion. We analyzed the structure of Cu2(pymca)3(ClO4), including superlattice reflections that were overlooked during previous X-ray diffraction studies of the material, and clarified that its distorted honeycomb lattice consists of Cu2(pymca)3 sections. Further investigation of Cu2(pymca)3(ClO4) crystal structure may reveal magnetic susceptibilities of the distorted honeycomb lattice.

DOI： 10.7566/JPSJ.86.123302

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記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：ACS Applied Materials and Interfaces  

High luminescence efficiency is obtained in halide- and chalcogenide-based phosphors, but they are impractical because of their poor chemical durability. Here we report a halide-based nanocomposite phosphor with excellent luminescence efficiency and sufficient durability for practical use. Our approach was to disperse luminescent single nanocrystals of CaI2:Eu2+ in a chemically stable, translucent crystalline SiO2 matrix. Using this approach, we successfully prepared a nanocomposite phosphor by means of self-organization through a simple solid-state reaction. Single nanocrystals of 6H polytype (thr notation) CaI2:Eu2+ with diameters of about 50 nm could be generated not only in a SiO2 amorphous powder but also in a SiO2 glass plate. The nanocomposite phosphor formed upon solidification of molten CaI2 left behind in the crystalline SiO2 that formed from the amorphous SiO2 under the influence of a CaI2 flux effect. The resulting nanocomposite phosphor emitted brilliant blue luminescence with an internal quantum efficiency up to 98% upon 407 nm violet excitation. We used cathodoluminescence microscopy, scanning transmission electron microscopy, and Rietveld refinement of the X-ray diffraction patterns to confirm that the blue luminescence was generated only by the CaI2:Eu2+ single nanocrystals. The phosphor was chemically durable because the luminescence sites were embedded in the crystalline SiO2 matrix. The phosphor is suitable for use in near-ultraviolet light-emitting diodes. The concept for this nanocomposite phosphor can be expected to be effective for improvements in the practicality of poorly durable materials such as halides and chalcogenides.

DOI： 10.1021/acsami.7b14132

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PubMed

記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：Physical Review Letters  

A quasi-one-dimensional organic charge-transfer salt (TMTTF)2PF6 undergoes a multistep phase transition as the temperature decreases. One of these transitions is called a "structureless transition," and these detailed structures were unknown for many years. With synchrotron x-ray diffraction, we observed a slight structural difference owing to the effect of charge-order transition between two TMTTF molecules in a dimer, which corresponds to the charge transfer δCO=0.20e. The two-dimensional Wigner crystallization was determined from an electron density analysis using core differential Fourier synthesis. Furthermore, we found that the ground state due to tetramerization, called the spin Peierls phase, is a three-dimensional transition with interchain correlation.

DOI： 10.1103/PhysRevLett.119.065701

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PubMed

記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：Physical Review B  

We have investigated crystal structure and magnetic properties of three S=1V3+ Ising-like anisotropic kagome lattice antiferromagnets, Cs2KV3F12,Cs2NaV3F12, and Rb2NaV3F12, using single crystals. Each compound crystallizes in a monoclinic system and has a slightly distorted kagome lattice. Although the magnetic properties are similar, the details depend on the magnitude of magnetic anisotropy. The magnetization and magnetic susceptibility are highly anisotropic owing to anisotropic g factors and Ising-like single ion anisotropy originating from partially unquenched orbital moments of V3+, and the easy axis of Ising-like anisotropy is perpendicular to the kagome plane. In contrast to disordered ground states in the isostructural Ti3+ (S=1/2) compounds, the V3+ (S=1) compounds exhibit antiferromagnetic ordering with distorted 120° structure or other nearly coplanar magnetic structure whose basal spin plane includes the easy axis, which is mainly due to large magnetic anisotropy and decrease of quantum fluctuation. Moreover, when magnetic fields are applied perpendicular to the kagome plane, magnetization curves of them show distinct 1/3 and 2/3 magnetization plateaus, which are stabilized by Ising-like single ion anisotropy. In particular, the 2/3 magnetization plateaus are notable magnetic phenomena in kagome lattice antiferromagnets and are due to the combination of spin frustration, Ising-like single ion anisotropy, and the small monoclinic distortion of kagome lattices.

DOI： 10.1103/PhysRevB.95.134436

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記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：Inorganic Chemistry  

Two novel 112-type palladium-doped iron arsenides were synthesized and identified using comprehensive studies involving synchrotron X-ray diffraction and X-ray absorption near-edge structure (XANES) experiments. Whereas in-plane arsenic zigzag chains were found in the 112-type superconducting iron arsenide Ca1-xLaxFeAs2 with maximum Tc = 34 K, deformed arsenic network structures appeared in other 112-type materials, such as longitudinal arsenic zigzag chains in CaFe1-yPdyAs2 (y ∼ 0.51) and arsenic square sheets constructed via hypervalent bonding in Ca1-xLaxFe1-yPdyAs2 (x ∼ 0.31, y ∼ 0.30). As K-edge XANES spectra clarified the similar oxidization states around FeAs4 tetrahedrons, alluding to possible parents for high-Tc 112-type iron arsenide superconductors.

DOI： 10.1021/acs.inorgchem.6b03115

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PubMed

記述言語：英語   掲載種別：研究論文（学術雑誌）  

DOI： 10.1038/srep39280

担当区分：筆頭著者   記述言語：英語  

DOI： 10.1107/S2052252516013889

記述言語：英語   掲載種別：研究論文（学術雑誌）  

DOI： 10.1073/pnas.1508941112

記述言語：英語   掲載種別：研究論文（学術雑誌）  

DOI： http://dx.doi.org/10.7566/JPSJ.83.113707

記述言語：英語   掲載種別：研究論文（学術雑誌）  

DOI： 10.1021/ja502733e

記述言語：英語   掲載種別：研究論文（学術雑誌）  

DOI： 10.1038/nmat3942

記述言語：英語   掲載種別：研究論文（学術雑誌）  

DOI： 10.7566

記述言語：英語   掲載種別：研究論文（学術雑誌）  

DOI： 10.1038/srep03101

記述言語：英語   掲載種別：研究論文（学術雑誌）  

DOI： 10.1038/ncomms2914

記述言語：英語   掲載種別：研究論文（学術雑誌）  

DOI： 10.1021/jp311948c

記述言語：英語   掲載種別：研究論文（学術雑誌）  

DOI： 10.1039/C3TA00011G

記述言語：英語   掲載種別：研究論文（学術雑誌）  

DOI： 10.1002/chem.201202056

記述言語：英語   掲載種別：研究論文（学術雑誌）  

DOI： 10.1038/ncomms2138

記述言語：英語   掲載種別：研究論文（学術雑誌）  

DOI： 10.1126/science.1212154

記述言語：英語   掲載種別：研究論文（学術雑誌）  

DOI： 10.1126/science.1212154

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記述言語：日本語   掲載種別：研究論文（学術雑誌）  

高輝度放射光による先端物性研究

記述言語：英語   掲載種別：研究論文（学術雑誌）  

記述言語：英語   掲載種別：研究論文（学術雑誌）  

DOI： 10.1103/PhysRevLett.103.073001

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記述言語：日本語

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記述言語：日本語  

J-GLOBAL

記述言語：日本語  

J-GLOBAL

記述言語：日本語  

J-GLOBAL

記述言語：日本語  

J-GLOBAL

記述言語：日本語  

J-GLOBAL

記述言語：日本語  

J-GLOBAL

記述言語：日本語  

J-GLOBAL

記述言語：日本語  

J-GLOBAL

記述言語：日本語  

J-GLOBAL

記述言語：日本語  

J-GLOBAL

記述言語：日本語   出版者・発行元：一般社団法人 日本物理学会  

<p>Cu_2_(pymca)_3_(ClO_4_)はスピン1/2を持つCu^2+^がハニカム格子を形成し、量子スピン液体状態が期待されていた。既報の構造解析の結果ではこのハニカム格子は厳密な正六角形をとり、Cu^2+^のeg軌道軌道の縮退が示唆されていたが、磁性等の物理データと整合しない点があり、正確な結晶構造を得るため、PFでの放射光X線回折実験を行った。。本講演では、既報の放射光X線回折実験によって求まった結晶構造について発表する。この構造は既報の構造と異なっている部分があり、そのことによりハニカム格子およびCu^2+^の取りうる電子状態がどのように変化するか発表する予定である。</p>

DOI： 10.11316/jpsgaiyo.72.1.0_1076

J-GLOBAL

記述言語：日本語  

J-GLOBAL

記述言語：日本語  

J-GLOBAL

記述言語：日本語  

J-GLOBAL

記述言語：日本語  

J-GLOBAL

記述言語：日本語   出版者・発行元：一般社団法人 日本物理学会  

<p>Cu_2_(pymca)_3_(ClO_4_)はCu^2+^が六角形に並んだ層がc軸方向に積み重なったスピン1/2ハニカム格子反強磁性体である。帯磁率の温度依存性を見ると26 K付近に低次元磁性体特有のブロードなピークが見られるが、2 Kまでの範囲で磁気秩序の徴候は見られなかった。講演では粉末試料を用いた70Tまでの強磁場磁化測定の結果とその解析について報告する。</p>

DOI： 10.11316/jpsgaiyo.72.1.0_1077

J-GLOBAL

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