巻号一覧
78 巻, 11 号
選択された号の論文の48件中1～48を表示しています
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Yasuki Nagai, Osamu Iwamoto, Nobuyuki Iwamoto, Tadahiro Kin, Mariko Se ...2009 年 78 巻 11 号 p. 113201
発行日: 2009/11/15
公開日: 2011/12/28
ジャーナル 認証あり90gY radiopharmaceuticals for cancer therapy have been used together with 111In radiopharmaceuticals for diagnostics, since a daughter nucleus of 90Sr, the ground state of 90Y, 90gY, is a pure β-ray emitting nucleus with no γ-ray emissions, providing no practical way for imaging. We have noted that the 682 keV isomeric state of 90Y, 90mY, with a half-life of 3.2 h as well as 90gY can be populated significantly by 90Zr(n,p)90Y and 93Nb(n,α)90Y at a neutron energy of 14 MeV. On the basis of the result, we have proposed a new method to use 90Y radiopharmaceuticals containing 90mY for diagnostics and 90gY for therapy, since the isomeric state decays to the ground state of 90Y by emitting 480 and 203 keV γ-rays, appropriate energies for imaging. 90Y radiopharmaceuticals containing 90mY could solve long-standing problems associated with the use of 90gY together with 111In for imaging.抄録全体を表示PDF形式でダウンロード (142K) -
Hiroki M. Adachi, Yasumasa Tsutsumi, Jukka A. M. Huhtamäki, Kazus ...2009 年 78 巻 11 号 p. 113301
発行日: 2009/11/15
公開日: 2011/12/28
ジャーナル 認証ありWe report on the fundamental properties of superfluids with d-wave pairing symmetry. We consider neutral atomic Fermi gases in a harmonic trap, the pairing being produced by a Feshbach resonance via a d-wave interaction channel. A Ginzburg–Landau (GL) functional is constructed, which is symmetrically constrained for five component order parameters (OPs). We find OP textures in the cyclic phase and stability conditions for a non-Abelian fractional 1/3-vortex under rotation. We propose a method of creating the interesting 1/3-vortex experimentally in atomic gases by optical means.抄録全体を表示PDF形式でダウンロード (1010K) -
Hao Ran Gong, Chao Ping Liang, Yue Hui He2009 年 78 巻 11 号 p. 113601
発行日: 2009/11/15
公開日: 2011/12/28
ジャーナル 認証ありFirst-principles calculations reveal that for Pd/TiAl interfaces the doping of C atoms at the surface centers of Pd interface layers could both increase the bond strength by a factor of 2 and decrease the interface energy by a factor of 3, suggesting that C would be a good doping candidate of increasing the lifetime of Pd/TiAl membranes. Calculations also show that although the addition of C atoms decreases the interface bond strength of Pd–Al and Pd–Ti bonds, the extra interface Ti–C and Al–C bonds are strong enough to induce the strengthening effect of the C doping.抄録全体を表示PDF形式でダウンロード (210K) -
Takanori Kida, Takahiro Matsunaga, Masayuki Hagiwara, Yoshikazu Mizugu ...2009 年 78 巻 11 号 p. 113701
発行日: 2009/11/15
公開日: 2011/12/28
ジャーナル 認証ありWe have performed electrical resistivity measurements of a polycrystalline sample of FeSe0.25Te0.75, which exhibits superconductivity at Tc∼14 K, in magnetic fields up to 55 T to determine the upper critical field μ0Hc2. In this compound, very large slopes of μ0Hc2 at the onset, the mid-point, the zero-resistivity temperatures on superconductivity are determined to be −13.7, −10.1, and −6.9 T/K, respectively. The observed μ0Hc2(T)s of this compound are considerably smaller than those expected from the Werthamer–Helfand–Hohenberg model, manifesting the Pauli limiting behavior. These results suggest that this compound shows the spin-singlet pairing in the superconducting state.抄録全体を表示PDF形式でダウンロード (299K) -
Tsutomu Watanabe, Sumio Ishihara2009 年 78 巻 11 号 p. 113702
発行日: 2009/11/15
公開日: 2011/12/28
ジャーナル 認証ありWe examine theoretically the possibility of ferroelectricity caused by electronic charge order without inversion symmetry motivated by layered iron oxides. Quantum electronic models in a paired-triangular lattice are analyzed by utilizing the variational Monte Carlo simulation. Our calculations demonstrate that the combined effects of electron transfer between the layers, corresponding to quantum fluctuation between the potential minima, and geometrical frustration promote the appearance of electric polarization. Our results contrast with the conventional manner of quantum fluctuation in ferroelectricity.抄録全体を表示PDF形式でダウンロード (180K) -
Tetsu Nobukuni, Hirono Kaneyasu, Nobuyuki Shima, Kenji Makoshi2009 年 78 巻 11 号 p. 113703
発行日: 2009/11/15
公開日: 2011/12/28
ジャーナル 認証ありThe effect of the site potential in an imperfect layer is studied in a d-wave layer superconductor on the basis of the electron correlation. The site potential binds electrons to the imperfect layer, and then, the superconductivity of the imperfect layer is independent of that of the bulk. We found that the superconducting transition temperature of the imperfect layer becomes higher than that of the bulk owing to the effect of the site potential. In this situation, the Fermi surface of the imperfect layer has a strong nesting feature leading to increases in both the antiferromagnetic spin fluctuation and the density of states near the Fermi level, which are in favor of d-wave pairing.抄録全体を表示PDF形式でダウンロード (196K) -
Taichi Kosugi, Takashi Miyake, Shoji Ishibashi, Ryotaro Arita, Hideo A ...2009 年 78 巻 11 号 p. 113704
発行日: 2009/11/15
公開日: 2011/12/28
ジャーナル 認証ありTo explore the electronic structure of the first aromatic superconductor, potassium-doped solid picene which has been recently discovered by Mitsuhashi et al. with the transition temperatures Tc=7–20 K, we have obtained a first-principles electronic structure of solid picene as a first step toward the elucidation of the mechanism of the superconductivity. The undoped crystal is found to have four conduction bands, which are characterized in terms of the maximally localized Wannier orbitals. We have revealed how the band structure reflects the stacked arrangement of molecular orbitals for both undoped and doped (K3picene) cases, where the bands are not rigid. The Fermi surface for K3picene is a curious composite of a warped two-dimensional surface and a three-dimensional one.抄録全体を表示PDF形式でダウンロード (3216K) -
Hitoshi Sugawara, Kenji Ishida, Yusuke Nakai, Hiroshi Yanagi, Toshio K ...2009 年 78 巻 11 号 p. 113705
発行日: 2009/11/15
公開日: 2011/12/28
ジャーナル 認証ありWe have performed magnetization and 31P-NMR measurements on the itinerant ferromagnet LaCoPO (Curie temperature TCurie∼44 K) with a layered structure in order to investigate spin dynamics in the paramagnetic state. The linear scaling between the Knight shift K at the P site and the bulk susceptibility χ above TCurie indicates that the 31P nucleus is suitable for investigating magnetic properties. The temperature and magnetic field dependences of the nuclear spin–lattice relaxation rate divided by the temperature 1⁄T1T at the P site show characteristic features of itinerant ferromagnets, such as ZrZn2 and Y(Co1−xAlx)2. In addition, the relationship between 1⁄T1T and χ above TCurie suggests that ferromagnetic fluctuations possess a two-dimensional (2D) characteristic. The present data show that LaCoPO is a unique ferromagnet, where the 2D fluctuations anticipated from the crystal structure are predominant down to almost TCurie.抄録全体を表示PDF形式でダウンロード (215K) -
Justin Panarin, Stéphane Raymond, Gérard Lapertot, Jacqu ...2009 年 78 巻 11 号 p. 113706
発行日: 2009/11/15
公開日: 2011/12/28
ジャーナル 認証ありThe evolution of the magnetic excitation spectrum of the unconventional superconductor CeCoIn5 was studied by inelastic neutron scattering as a function of magnetic field applied in the [1,−1,0] direction. The spin resonance characteristic of the superconducting state was observed up to about Hc2⁄2: it is still centered at (1⁄2,1⁄2,1⁄2) when the magnetic field increases while its characteristic energy decreases and its lineshape substantially broadens.抄録全体を表示PDF形式でダウンロード (213K) -
Ryotaro Arita, Hiroaki Ikeda2009 年 78 巻 11 号 p. 113707
発行日: 2009/11/15
公開日: 2011/12/28
ジャーナル 認証ありWe study whether Fermi-surface (FS) nesting can give rise to high-temperature superconductivity in iron pnictides. Starting with ab initio construction of an effective four-orbital model, we employ the fluctuation–exchange approximation to show that FS does not necessarily favor the stripe antiferromagnetic order observed in experiments, especially for realistic electronic correlations. If superconductivity in iron pnictides is magnetically mediated and has a fully gapped sign-reversing s-wave symmetry, our results suggest that the pairing interaction does not arise only from FS nesting and that exchange interactions between local moments in the Fe 3d orbitals may play a crucial role.抄録全体を表示PDF形式でダウンロード (266K) -
Hideaki Sakai, Yasujiro Taguchi, Yoshinori Tokura2009 年 78 巻 11 号 p. 113708
発行日: 2009/11/15
公開日: 2011/12/28
ジャーナル 認証ありVariation of magnetocaloric (MC) effects has been systematically investigated for colossal magnetoresistive (CMR) manganites R0.6Sr0.4MnO3 (R = La–Gd). As the one-electron bandwidth is reduced, the temperature profile of MC effect, i.e. field-induced entropy change, exhibits a steeper drop below the ferromagnetic transition temperature due to its first-order nature promoted by a competing charge-orbital ordering instability. For these small-bandwidth systems adjacent to the metal–insulator phase boundary, a rectangular-shaped profile for the entropy change emerges with an anomalously wide temperature range and a considerable magnitude. Model calculations have indicated that the fluctuation enhanced in the phase-competing region has a strong impact on such MC features.抄録全体を表示PDF形式でダウンロード (368K) -
Dai Aoki, Tatsuma D. Matsuda, Valentin Taufour, Elena Hassinger, Georg ...2009 年 78 巻 11 号 p. 113709
発行日: 2009/11/15
公開日: 2011/12/28
ジャーナル 認証ありMagnetoresistivity measurements with fine tuning of the field direction on high quality single crystals of the ferromagnetic superconductor UCoGe show anomalous anisotropy of the upper critical field Hc2. Hc2 for H||b-axis (Hc2b) in the orthorhombic crystal structure is strongly enhanced with decreasing temperature with an S-shape and reaches nearly 20 T at 0 K. The temperature dependence of Hc2a shows upward curvature with a low temperature value exceeding 30 T, while Hc2c at 0 K is very small (∼0.6 T). Contrary to conventional ferromagnets, the decrease of the Curie temperature with increasing field for H||b-axis marked by an enhancement of the effective mass of the conduction electrons appears to be the origin of the S-shaped Hc2b curve. These results indicate that the field-induced ferromagnetic instability or magnetic quantum criticality reinforces superconductivity.抄録全体を表示PDF形式でダウンロード (364K) -
Kenta Kimura, Tsuyoshi Otani, Hiroyuki Nakamura, Yusuke Wakabayashi, T ...2009 年 78 巻 11 号 p. 113710
発行日: 2009/11/15
公開日: 2011/12/28
ジャーナル 認証ありWe investigated magnetostrictive properties of a triangular lattice antiferromagnet CuCrO2 showing an incommensurate proper-screw spin order by means of x-ray diffraction and strain gauge measurements. A deformation of the triangular lattice plane leading to a lowered crystallographic symmetry was found upon the magnetic ordering, which demonstrates a strong spin–lattice coupling in this system. The resultant multiple structural domains can be successfully arranged by magnetic field cooling procedures. We discuss the relationship between the lattice distortion and incommensurability in CuCrO2.抄録全体を表示PDF形式でダウンロード (254K) -
Kazuyuki Hara, Yoichi Nakayama, Seiji Miyoshi, Masato Okada2009 年 78 巻 11 号 p. 114001
発行日: 2009/11/15
公開日: 2011/12/28
ジャーナル 認証ありWe propose a new mutual learning using many weak learners (or students) which converges into the identical state of Bagging that is kind of ensemble learning, within the framework of on-line learning, and have analyzed its asymptotic property through the statistical mechanics method. Mutual learning involving three or more students fundamentally differs from the two-student case with regard to the variety of selecting a student to act as teacher. The proposed model consists of two learning steps: many students independently learn from a teacher, and then the students learn from others through the mutual learning. In mutual learning, students learn from other students and the generalization error is improved even if the teacher has not taken part in the mutual learning. We demonstrate that the learning style of selecting a student to act as teacher randomly is superior to that of cyclic order by using principle component analysis.抄録全体を表示PDF形式でダウンロード (192K) -
Zhifeng Chen, Chengguang Bao, Zhibing Li2009 年 78 巻 11 号 p. 114002
発行日: 2009/11/15
公開日: 2011/12/28
ジャーナル 認証ありThe spin mixing dynamics of spin-1 Bose–Einstein condensates with zero magnetization and under an external magnetic field is investigated in a systematic way. Beyond the mean field theory, the time-dependent solutions of the Hamiltonian under the single mode approximation are obtained via a procedure of diagonalization. Thereby the time-dependent populations of spin-0 component starting from various initial states are obtained and analyzed. The features of evolution are compared in detail with those with the field removed so as to emphasize the effect of the field. Since the solutions are exact for the Hamiltonian, we can study the long-term behavior of the evolution, where periodicity and inherent symmetry emerge. In particular, some special cases are found in which the evolution is highly sensitive to the field, very strong oscillation in population can be thereby induced. A new mode of oscillation of the population characterized by having two frequencies, one is high and one is low, is found when the field is sufficiently strong.抄録全体を表示PDF形式でダウンロード (957K) -
Kazufumi Sato, Satoshi Takizawa, Seiji Miura, Tetsuo Mohri2009 年 78 巻 11 号 p. 114003
発行日: 2009/11/15
公開日: 2011/12/28
ジャーナル 認証ありWe perform kinetic Monte Carlo simulations of atomic diffusion in the Ti–Al system using activation energies calculated by embedded atom method (EAM). The activation energies strongly depend on the atomic species occupying the four atomic sites which locate nearest to the saddle point in the fcc lattice. It is found, however, that the configuration of atoms on the other sites surrounding the jumping atom plays an essential role in the atomic ordering process: we fail to reproduce the formation of ordered nuclei in using the activation energies which depend only on the configuration of the nearest four atoms, and the system remains in disordered states even at very low temperatures. By introducing a correction term to the activation energies which takes into account the contribution of nearest neighbor atoms of the migrating atom, we can simulate growth of ordered embrios.抄録全体を表示PDF形式でダウンロード (164K) -
Yusuke Tomita2009 年 78 巻 11 号 p. 114004
発行日: 2009/11/15
公開日: 2011/12/28
ジャーナル 認証ありTwo-dimensional Heisenberg dipolar lattices are investigated by Monte Carlo simulations. Simulations are performed on triangular, square, honeycomb, and kagomé lattices. Lattice-dependent magnetic structures and critical phenomena are observed. Although it is believed that two-dimensional Heisenberg dipolar lattices belong to the same universality class of two-dimensional XY dipolar lattices, results from the Monte Carlo simulations show considerable deviations in the critical exponent ν between the Heisenberg and XY models of triangular and square lattices. The Heisenberg dipolar honeycomb lattice exhibits unusual magnetic ordering in the form of arrays of vortices. Using finite-size scaling techniques, it is shown that the unusual order undergoes the Kosterlitz–Thouless transition. On the kagomé lattice, geometric frustration produces a peculiar ferromagnetic ordered state that is macroscopically degenerate. The degeneracy is expected to explain the missing magnetic entropy in ferromagnetic kagomé, pyrochlore, and spinel substances.抄録全体を表示PDF形式でダウンロード (534K) -
Akiko Masaki, Hiroyuki Mori2009 年 78 巻 11 号 p. 114301
発行日: 2009/11/15
公開日: 2011/12/28
ジャーナル 認証ありWe performed quantum Monte Carlo calculations to investigate the detail of local Mott states formed in Bose–Fermi mixtures confined in an optical lattice. The density profile of Bose–Fermi mixtures confined in an optical lattice could have some flat density domains, known as Mott plateaus, when the local density meets a certain criterion. By looking into the domains, we found an interesting tendency that the ratio of the density of the bosons to that of the fermions within the domains was given by a ratio of simple integers. We discuss the implications of the tendency.抄録全体を表示PDF形式でダウンロード (114K) -
Rameez-ul-Islam, Ashfaq H. Khosa, Farhan Saif2009 年 78 巻 11 号 p. 114401
発行日: 2009/11/15
公開日: 2011/12/28
ジャーナル 認証ありWe suggest a simple method to generate cluster states of two-level atoms. The protocol utilizes minimum cavity/atomic resources and is based upon standard cavity QED tools alongwith Ramsey technique. Two identical atoms, each initially prepared in coherent superposition, interact simultaneously with an initially vacuum state cavity for a specified time. One atom has resonant interactions while at the same time the other one interacts dispersively. When, after completion of the interaction, cavity is again left into vacuum then atoms are shown to be entangled in bipartite cluster state. The method is also generalized to generate multi-partite linear cluster states as well as the atomic graph states.抄録全体を表示PDF形式でダウンロード (1892K) -
Hidetsugu Sakaguchi2009 年 78 巻 11 号 p. 114402
発行日: 2009/11/15
公開日: 2011/12/28
ジャーナル 認証ありWe investigate a mechanism of the appearance of kinetic friction in granular materials. We consider a small number of intervening inelastic particles between two rough surfaces as one of the simplest dynamical models to study granular friction. The resistance force applied to the upper surface is numerically calculated. We find that the resistance force F(t) is scaled as F′(vt) for a small pulling velocity v. The time average F0=‹F(t)› in the limit v→0 is not zero owing to the mutual collisions between the intervening particles. The nonzero F0 implies the appearance of kinetic friction in this simple dynamical system.抄録全体を表示PDF形式でダウンロード (843K) -
Do Ngoc Son, Hiroshi Nakanishi, Melanie Yadao David, Hideaki Kasai2009 年 78 巻 11 号 p. 114601
発行日: 2009/11/15
公開日: 2011/12/28
ジャーナル 認証ありWe investigate the oxygen reduction reaction (ORR) on Pt(111) surface in the presence of hydronium ion. The ORR is proposed to proceed through two adsorption pathways: one is through the dissociative adsorption that forms adsorbed oxygen atoms Oad on the surface (“ad” means in the adsorbed state on the surface), followed by a reductive transition in the presence of hydronium ion that transits Oad into the adsorbed hydroxyl (OH)ad. In this pathway, the first electron transfers after dissociation of O2; the other is through the molecular adsorption on the surface, followed by a reductive adsorption in the presence of hydronium ion in which first electron transfers after the O2 adsorption to form the adsorbed end-on intermediate OadOH before continuing the reaction with another hydronium ion to form the adsorbed hydroxyl (OH)ad. In both cases, the reaction is completed by the reductive desorption of (OH)ad in the presence of hydronium ion to form water molecules. In this work, we focus our study on the reductive transition in the first pathway and the reductive adsorption in the second pathway. Through adiabatic potential energy for the proton motion from hydronium ion to the Pt surface, the isolated state of H3O+ from the Pt surface is determined, which is then used as the initial state for studying the potential energy of hydronium motion. In addition, the optimized structures for the reaction intermediates are also obtained. Comparing the results of non-hydrated and hydrated H3O+, we find that increasing the number of water molecules stabilizes the (OH)ad in the reductive transition and the OadOH in the reductive adsorption. Moreover, water molecules generate the activation barrier for the OadOH intermediate formation in the reductive adsorption.抄録全体を表示PDF形式でダウンロード (4688K) -
Santanu K. Maiti2009 年 78 巻 11 号 p. 114602
発行日: 2009/11/15
公開日: 2011/12/28
ジャーナル 認証ありWe describe XNOR gate response in a mesoscopic ring threaded by a magnetic flux φ. The ring is attached symmetrically to two semi-infinite one-dimensional metallic electrodes and two gate voltages, viz., Va and Vb, are applied in one arm of the ring which are treated as the inputs of the XNOR gate. The calculations are based on the tight-binding model and the Green’s function method, which numerically compute the conductance–energy and current–voltage characteristics as functions of the ring-to-electrode coupling strength, magnetic flux and gate voltages. Our theoretical study shows that, for a particular value of φ (=φ0⁄2) (φ0=ch⁄e, the elementary flux-quantum), a high output current (1) (in the logical sense) appears if both the two inputs to the gate are the same, while if one but not both inputs are high (1), a low output current (0) results. It clearly exhibits the XNOR gate behavior and this aspect may be utilized in designing an electronic logic gate.抄録全体を表示PDF形式でダウンロード (309K) -
Yoji Kubota, Katsuyuki Nobusada2009 年 78 巻 11 号 p. 114603
発行日: 2009/11/15
公開日: 2011/12/28
ジャーナル 認証ありWe verify the practical applicability of the conventional site-basis time-evolution equation to exciton transfer processes in a quantum-dot array model. The time-evolution equation has proved to work under the rather limited conditions of the zero temperature limit and/or a minimal two-dot system. The computed results dramatically change with the temperature, the number of quantum dots, and the intensity of transition rates between adjacent sites. This is due to the fact that the higher-order perturbation terms, which are neglected in deriving the site-basis equation, have a great influence on the exciton dynamics. We found that the thermal relaxation can be suppressed by controlling the dot size and interdot distance.抄録全体を表示PDF形式でダウンロード (212K) -
Hiroto Kozuka, Yoshihiro Ikeda, Masami Kawaguchi2009 年 78 巻 11 号 p. 114604
発行日: 2009/11/15
公開日: 2011/12/28
ジャーナル 認証ありThe buoyancy-driven path instabilities of an air bubble rising in a Hele–Shaw cell filled with pure water and aqueous poly(N-isopropyl acrylamide) (PNIPAM) solutions are examined as a function of the Eötvös number (Eo) by measuring changes in the bubble shape, the trajectory, and the peripheral length of a bubble (L) as well as the visualization of the wake structures behind the bubble. The instabilities can be categorized into four regimes: (1) an oblate ellipse bubble accompanied with a vibrational trajectory, no changes in L, and a Kármán vortex street for the wake structure, (2) a comma-shaped bubble with a vibrational motion of both path and L, together with a vortex street different from a Kármán one, and (3) changes in the bubble shape, such as a comma-shaped bubble and a jellyfish one with a vibration of both path and L accompanied with a vortex street different from a Kármán one, and (4) changes in the bubble shape, such as a bird flapping its wings bubble and a jellyfish one with a straight trajectory, a vibration of L, and no vortex streets. However, in the PNIPAM solution, vibrations of path and L are somewhat suppressed by adsorption of PNIPAM on the bubble surface and no bird flapping its wings bubble is observed.抄録全体を表示PDF形式でダウンロード (1513K) -
Dong-Seok Yang, Narkeon Sung, Tae Ho Yeom2009 年 78 巻 11 号 p. 114605
発行日: 2009/11/15
公開日: 2011/12/28
ジャーナル 認証ありThe local structure of Fe doped LiNbO3 crystal fabricated by the Czochralski technique was examined by X-ray absorption fine structure analysis. We found that Fe3+ was dominant in LiNbO3:Fe (0.1%), and that Fe atoms occupied Li atomic sites in LiNbO3 crystal. Also, we found that the local structure around Fe atoms is highly disordered so that the higher shells with structural periodicity disappeared.抄録全体を表示PDF形式でダウンロード (141K) -
Yasumasa Tsutsumi, Kazushige Machida2009 年 78 巻 11 号 p. 114606
発行日: 2009/11/15
公開日: 2011/12/28
ジャーナル 認証ありMotivated by the on-going rotating cryostat experiments in ISSP, University of Tokyo, we explore the textures and vortices in superfluid 3He-A phase confined in narrow cylinders, whose radii are R=50 μm and 115 μm. The calculations are based on the Ginzburg–Landau (GL) framework, which fully takes into account the orbital (l-vector) and spin (d-vector) degrees of freedom for chiral p-wave pairing superfluid. The GL free energy functional is solved numerically by using best known GL parameters appropriate for the actual experimental situations at P=3.2 MPa and H=21.6 mT. We identify the ground state l-vector configuration as radial disgyration (RD) texture with the polar core both at rest and low rotations and associated d-vector textures for both narrow cylinder systems under high magnetic fields. The RD which has a singularity at center changes into Mermin–Ho texture above the critical rotation speed. This is determined precisely. The consequences are compared with experimental results.抄録全体を表示PDF形式でダウンロード (1494K) -
Takao Sekiya, Nozomi Kamiya, Shohei Ohya, Susumu Kurita, Tetsuya Kodai ...2009 年 78 巻 11 号 p. 114701
発行日: 2009/11/15
公開日: 2011/12/28
ジャーナル 認証ありElectron paramagnetic resonance (EPR) measurements revealed the inclusion of nitrogen in yellow anatase single crystals grown by chemical vapor transport using NH4Cl as the transport agent. The angular-dependence of EPR triplets suggests that nitrogen occupies a substitutional site of oxygen in the bulk. The paramagnetic nitrogen observed at room temperature becomes diamagnetic at lower temperatures by trapping another electron. Below 50 K, only one symmetric differential EPR signal from titanium with an unpaired electron can be observed. These changes in the electric states of nitrogen and titanium can be explained by the presence of oxygen vacancies and by the contribution of trapped electrons to oxygen vacancies. The optical absorption observed at 3.0 eV in an E||a configuration, which is characteristic of yellow anatase is almost independent of temperature.抄録全体を表示PDF形式でダウンロード (470K) -
Takao Morinari, Hiroki Nakamura, Masahiko Machida, Takami Tohyama2009 年 78 巻 11 号 p. 114702
発行日: 2009/11/15
公開日: 2011/12/28
ジャーナル 認証ありIn layered single band systems, the interlayer conductivity depends on the orientation of the in-plane magnetic field and takes maximum values when the magnetic field is perpendicular to flat regions of the Fermi surface. Extending this known results to multi-band systems, we propose an experiment to extract information about their Fermi surface topology. We discuss application of the formula to a FeAs-based superconductor, LaFeAsO1−xFx. We show that the magnetically ordered state in the parent compound is clearly distinguished from the paramagnetic state by the oscillation period in the interlayer conductivity. We demonstrate that evolution of the Fermi surface topology by changing the doping concentration is reflected to the interlayer conductivity oscillation patterns.抄録全体を表示PDF形式でダウンロード (203K) -
Masato Matsuura, Maiko Kofu, Hiroyuki Kimura, Kazuma Hirota2009 年 78 巻 11 号 p. 114703
発行日: 2009/11/15
公開日: 2011/12/28
ジャーナル 認証ありWe have studied magnetic excitations in impurity-doped La1.85Sr0.15Cu1−yAyO4 (A=Ni or Zn) by neutron scattering. The dispersion for Zn:y=0.017 is similar to that for the impurity-free sample: incommensurate peaks with incommensurability δ=0.12±0.01 (rlu) do not change their positions up to 21 meV. On the other hand, for Ni:y=0.029, two incommensurate peaks observed at low energies suddenly change into a single broad commensurate peak at Ecross=15 meV. Compared with that for the impurity-free sample with a similar Sr concentration of x=0.16, Ecross for Ni:y=0.029 is decreased by nearly the same factor as the reduction in Tc. This is very similar to the shift of resonance energy (Eres) in Ni-doped YBa2Cu3O7. These common impurity effects on the shifts of Ecross and Eres suggest the same magnetic origin of the resonance peak in YBa2Cu3O6+x and that of the crossing point of upward and downward dispersions in La2−xSrxCuO4. We propose that the sudden change in the dispersions is better described by a crossover from incommensurate spin fluctuations to a gapped spin wave rather than an hourglass-like dispersion.抄録全体を表示PDF形式でダウンロード (195K) -
Shugo Ikeda, Hironori Sakai, Naoyuki Tateiwa, Tatsuma D. Matsuda, Dai ...2009 年 78 巻 11 号 p. 114704
発行日: 2009/11/15
公開日: 2011/12/28
ジャーナル 認証ありWe studied the magnetic properties of the paramagnet β-US2 with an orthorhombic crystal structure by measuring its magnetization, magnetic susceptibility, specific heat, and electrical resistivity under magnetic field and pressure. The 5f-crystalline electric field (CEF) scheme was determined from the experimental results: a singlet in the ground state and a pseudo-doublet in the first excited state, separated by 85 and 91 K from the ground state. The insulating resistivity markedly changes to a metallic one under a high pressure of 8 GPa similarly to that of the semimetallic Ising-type ferromagnet UTeS with a Curie temperature TC=87 K. A resistivity anomaly was also observed in the temperature dependence of the resistivity under pressure, most likely corresponding to ferromagnetic ordering. From these experimental results, it was concluded that β-US2 is in the vicinity of ferromagnetic ordering at ambient pressure. Furthermore, we found that the easy-axis magnetization at low fields for H||[001] consists of a linear magnetization based on the 5f-CEF scheme and a ferromagnetic-like magnetization with a saturated moment of 0.042 μB/U. The latter magnetization was analyzed on the basis of the ferromagnetic cluster and discussed from the viewpoint of the magnetic polaron.抄録全体を表示PDF形式でダウンロード (1391K) -
Takumi Yonemura, Hiroshi Tanida, Masafumi Sera, Fumitoshi Iga2009 年 78 巻 11 号 p. 114705
発行日: 2009/11/15
公開日: 2011/12/28
ジャーナル 認証ありWe have studied the thermal and transport properties of NdB6 focused on the anisotropic behaviors depending on the applied magnetic field direction. The magnetic field dependence of the physical properties in the type-I antiferromagnetic phase is small for H||[001] or [110] but is large for H||[111]. These anisotropic behaviors are associated with the different domain distribution depending on the applied magnetic field direction. For H||[001] or [110], the domain with only the χ⊥ component is realized, and for H||[111], that with both the χ⊥ and χ|| components is realized, where the competition among the crystalline electric field effect leading to the three-fold easy axis and the O20-type ferro-quadrupole interaction leading to the four-fold easy axis and also the antiferromagnetic interaction plays an important role. This competition might be important for the appearance of the successive metamagnetic phase transitions for H||[111]. The anisotropic behaviors of the magnetization, the specific heat and the electrical resistivity depending on the applied magnetic field direction in the type I-AFMI phase were analized by the mean field calculation by considering the different domain distribution depending on the magnetic field direction and could explain the characteristics of these anisotropic behaviors in low magnetic field region in the AFMI phase rather well.抄録全体を表示PDF形式でダウンロード (418K) -
Chie Tonohiro, Yasunori Nakano, Fuminori Honda, Tsutomu Yamada, Tetsuy ...2009 年 78 巻 11 号 p. 114706
発行日: 2009/11/15
公開日: 2011/12/28
ジャーナル 認証ありWe succeeded in growing the single crystals of RPt2Ge2 (R: La–Ho) with the monoclinic LaPt2Ge2-type structure. Most of RPt2Ge2 compounds order antiferromagnetically, approximately following the de Gennes scaling. Among them, CePt2Ge2 with a Néel temperature TN1=2.4 K indicates a change of the magnetic structure below TN2=1.8 K, with an ordered moment of 0.70 μB/Ce. The pressure experiment was also carried out for CePt2Ge2 by measuring the electrical resistivity. The critical pressure, where the Néel temperature becomes zero, is 7–8 GPa at which the heavy fermion state is realized. Superconductivity was, however, not observed experimentally.抄録全体を表示PDF形式でダウンロード (3334K) -
Tadashi Adachi, Keisuke Omori, Yoichi Tanabe, Yoji Koike2009 年 78 巻 11 号 p. 114707
発行日: 2009/11/15
公開日: 2011/12/28
ジャーナル 認証ありThe possible inhomogeneity of superconductivity has been investigated by means of bulk-sensitive probes, using La2−xSrxCuO4 (LSCO) single crystals from the underdoped to optimally doped regime. Measurements of the magnetic susceptibility, χ, on field cooling and specific heat have revealed that both the absolute value of χ at 2 K, regarded as corresponding to the superconducting (SC) volume fraction in a sample, and the Sommerfeld constant, reflecting the density of states of quasiparticles at the Fermi level, exhibit significant dependence on x, namely, on the hole concentration. This is the first experimental work strongly suggesting that a phase separation into SC and normal-state regions takes place in the underodped regime of LSCO as well as in the overdoped regime.抄録全体を表示PDF形式でダウンロード (252K) -
Takeshi Nakanishi, Tsuneya Ando2009 年 78 巻 11 号 p. 114708
発行日: 2009/11/15
公開日: 2011/12/28
ジャーナル 認証ありOptical response of finite-length metallic carbon nanotubes is calculated including effects of induced edge charges in a self-consistent manner. The results show that the main resonance corresponding to excitation of the fundamental plasmon mode with wave vector π⁄l with l being the tube length is quite robust and unaffected. This arises because the strong electric field associated with edge charges is screened and decays rapidly inside the nanotube. For higher-frequency resonances, the field starts to be mixed and tends to shift resonances to higher frequencies.抄録全体を表示PDF形式でダウンロード (1557K) -
Kazuki Iida, Hirofumi Ishikawa, Toshihiro Yamase, Taku J. Sato2009 年 78 巻 11 号 p. 114709
発行日: 2009/11/15
公開日: 2011/12/28
ジャーナル 認証ありInelastic neutron scattering (INS) experiments have been performed on a V3 triangular spin cluster. At the base temperature (T=0.7 K), the INS spectrum clearly exhibits a broad peak at hω=0.8 meV. The peak was ascribed to the superposition of four magnetic excitations from two Stotal=1⁄2 doublets to two Stotal=3⁄2 doublets. From the observed peak position, width, and intensity, we confirmed a model Hamiltonian comprising anisotropic exchange and Dzyaloshinsky–Moriya (DM) interactions, and estimated the Hamiltonian parameters as Jx=Jy=−5.73 K, Jz=−6.83 K, D1,2z=0.261 K, and D2,3z=D3,1z=0.287 K, where Jα is the α-component of the exchange interactions and Di,jz represents the z-component of the DM vector between the i-th and j-th V4+ ions. The resulting model Hamiltonian successfully reproduced the half-step magnetization process reported earlier as well as magnetic susceptibility.抄録全体を表示PDF形式でダウンロード (212K) -
Kichizo Asai, Takafumi Kawakami, Shumpei Enoshita, Masanori Shiozawa, ...2009 年 78 巻 11 号 p. 114710
発行日: 2009/11/15
公開日: 2011/12/28
ジャーナル 認証ありThe hyperfine magnetic field HHF at 55Mn in ferromagnetically ordered double perovskites La1−xBixMn0.5Ni0.5O3 with 0≤x≤0.9 were investigated by NMR at 1.8 K. HHF decreases with increasing Bi content x from −258 kOe at x=0 to approximately −280 kOe at x=0.9, which is attributed to a reduction in the positive supertransferred hyperfine magnetic field, HSTHF, from neighboring Ni2+ ions. The reduction in HSTHF caused by the Bi substitution suggests that the covalent character of Ni2+–O2−–Mn4+ bonds decreases in competition with that of Bi3+–O2− bonds. The decrease in the ferromagnetic Curie temperature of the present system with increasing x is quantitatively interpreted with the decreasing covalent character of Ni2+–O2−–Mn4+ bonds.抄録全体を表示PDF形式でダウンロード (282K) -
Akito Kobayashi, Yoshikazu Suzumura, Hidetoshi Fukuyama, Mark O. Goerb ...2009 年 78 巻 11 号 p. 114711
発行日: 2009/11/15
公開日: 2011/12/28
ジャーナル 認証ありThe possible quantum Hall ferromagnet at a filling factor ν=0 is investigated for the zero-energy (N=0) Landau level of the two dimensional massless Dirac fermions in α-(BEDT-TTF)2I3 under pressure with tilted cones and a twofold valley degeneracy resulting from time-reversal symmetry. In the case of the Dirac cones without tilting, the long-range Coulomb interaction in the N=0 Landau level exhibits the SU(2) valley-pseudo-spin symmetry even to the order O(a⁄lH), in contrast to N≠0 Landau levels, where a and lH represent the lattice constant and the magnetic length, respectively. Such a characteristic comes from a fact that zero-energy states in a particular valley are restricted to only one of the spinor components, whereas the other spinor component is necessarily zero. In the case of the tilted Dirac cones as found in α-(BEDT-TTF)2I3, one obtains a non-zero value of the second component and then the backscattering processes between valleys becomes non-zero. It is shown that this fact can lead to easy-plane pseudospin ferromagnetism (XY-type). In this case, the phase fluctuations of the order parameters can be described by the XY model leading to Kosterlitz–Thouless transition at lower temperature. In view of these theoretical results, experimental findings in resistivity of α-(BEDT-TTF)2I3 are discussed.抄録全体を表示PDF形式でダウンロード (337K) -
Shinnosuke Suzuki, Shigeki Miyasaka, Setsuko Tajima, Takanori Kida, Ma ...2009 年 78 巻 11 号 p. 114712
発行日: 2009/11/15
公開日: 2011/12/28
ジャーナル 認証ありWe have investigated the fluorine-doping dependence of lattice constants, transports and specific heat for polycrystalline LaFePO1−xFx. F doping slightly and monotonically decreases the in-plane lattice parameter. In the normal state, electrical resistivity at low temperature is proportional to the square of temperature and the electronic specific heat coefficient has large value, indicating the existence of moderate electron–electron correlation in this system. Hall coefficient has large magnitude, and shows large temperature dependence, indicating the low carrier density and multiple carriers in this system. Temperature dependence of the upper critical field suggests that the system is a two gap superconductor. The F-doping dependence of these properties in this system are very weak, while in the FeAs system (LaFeAsO), the F doping induces the large changes in electronic properties. This difference is probably due to the different F-doping dependence of the lattice in these two systems. It has been revealed that a pure effect of electron doping on electronic properties is very weak in this Fe pnictide compound.抄録全体を表示PDF形式でダウンロード (244K) -
Masahiko Isobe, Shigenori Koishi, Satoshi Yamazaki, Jun-ichi Yamaura, ...2009 年 78 巻 11 号 p. 114713
発行日: 2009/11/15
公開日: 2011/12/28
ジャーナル 認証ありThe effect of the substitution of various ions on the metal–insulator (MI) transition at 170 K in K2V8O16 has been investigated. Both Rb and Ti form complete solid solution systems: K2−xRbxV8O16 and K2V8−yTiyO16, respectively. The substitution of Rb for K or of Ti for V splits the transition into two transitions: the high-temperature transition is a first-order MI transition from a tetragonal structure to a tetragonal structure, and the low-temperature transition is a second-order transition to a monoclinic structure. In K2−xRbxV8O16, the former terminates to an MI transition at around 220 K in Rb2V8O16, while the latter disappears at x>0.6. In K2V8−yTiyO16, both transitions disappear at y>0.5. The substitution of Cr for V also results in a similar splitting of the transition and the rapid disappearance of both transitions. The substitution of Na or Ba for K suppresses the MI transition without any splitting of the transition, although the solubility of both ions is limited. These substitution effects reveal that the MI transition of K2V8O16 consists of two parts: a first-order MI transition and a parasitic second-order structural transition; the substitution of some ions causes a clear splitting of these transitions, probably due to the difference between the chemical pressure effects on the two transitions. The first-order MI transition is very sensitive to charge randomness, suggesting the charge ordering nature of the MI transition, while the second-order structural transition is very sensitive to both charge and structural randomnesses.抄録全体を表示PDF形式でダウンロード (1909K) -
Ryusuke Kondo, Seiichi Kagoshima, Naoya Tajima, Reizo Kato2009 年 78 巻 11 号 p. 114714
発行日: 2009/11/15
公開日: 2011/12/28
ジャーナル 認証ありWe perform crystal structure analyses of the organic conductor α-(BEDT-TTF)2I3 [where BEDT-TTF denotes bis(ethylene)dithiotetrathiafulvalene] and its selenium analogue α-(BEDT-TSeF)2I3 [where BEDT-TSeF denotes bis(ethylene)dithiotetraselenafulvalene] at room temperature under hydrostatic pressure, where they are expected to have zero-gap points at the Fermi level with a Dirac-cone-type dispersion for a massless particle. We calculate the electronic band structures using a combination of the extended Hückel molecular orbital calculation based on the obtained crystal structures and the tight-binding band structure calculation. We find that I) the obtained Fermi surfaces of both salts under hydrostatic pressure are simply larger than those at ambient pressure owing to an increase in overlap integrals caused by the pressure, and II) electronic structures having zero-gap points with a Dirac-cone-type dispersion at the Fermi level are realized only in α-(BEDT-TTF)2I3 by the introduction of suitable site potentials in wide parameter areas. These results suggest that, to realize such a unique electronic structure in this class of materials, some mechanisms are needed to effectively give the site potentials employed in this study. Examples are electronic correlation effects and I3 anion potentials.抄録全体を表示PDF形式でダウンロード (547K) -
Youichi Yanase, Manfred Sigrist2009 年 78 巻 11 号 p. 114715
発行日: 2009/11/15
公開日: 2011/12/28
ジャーナル 認証ありThe antiferromagnetic Fulde–Ferrell–Larkin–Ovchinnikov (AFM-FFLO) state of coexisting d-wave FFLO superconductivity and incommensurate AFM order is studied on the basis of Bogoliubov–de Gennes (BdG) equations. We show that the incommensurate AFM order is stabilized in the FFLO state by the appearance of the Andreev bound state localized around the zeros of the FFLO order parameter. The AFM-FFLO state is further enhanced by the induced π-triplet superconductivity (pair density wave). The AFM order occurs in the FFLO state even when it is neither stable in the normal state nor in the BCS state. The order parameters of the AFM order, d-wave superconductivity, and π-triplet pairing are investigated by focusing on their spatial structures. Roles of the spin fluctuations beyond the BdG equations are discussed. Their relevance to the high-field superconducting phase of CeCoIn5 is discussed.抄録全体を表示PDF形式でダウンロード (317K) -
Koichi Kusakabe2009 年 78 巻 11 号 p. 114716
発行日: 2009/11/15
公開日: 2011/12/28
ジャーナル 認証ありWe propose a possible charge fluctuation effect expected in layered superconducting materials. In the multireference density functional theory, relevant fluctuation channels for the Josephson coupling between superconducting layers include the interlayer pair hopping derived from the Coulomb repulsion. When interlayer single-electron tunneling processes are irrelevant in the Kohn–Sham electronic band structure calculation, the two-body effective interactions stabilize a superconducting phase. This state is also regarded as a valence-bond solid in a bulk electronic state. The hidden order parameters coexist with the superconducting order parameter when the charging effect of a layer is comparable to the pair hopping. Relevant material structures favorable for the pair-hopping mechanism are discussed.抄録全体を表示PDF形式でダウンロード (205K) -
Jun Kitazono, Toshiaki Omori, Masato Okada2009 年 78 巻 11 号 p. 114801
発行日: 2009/11/15
公開日: 2011/12/28
ジャーナル 認証ありAn associative memory model and a neural network model with a Mexican-hat type interaction are two major attractor neural network models. The associative memory model has discretely distributed fixed-point attractors, and achieves a discrete information representation. On the other hand, a neural network model with a Mexican-hat type interaction uses a ring attractor to achieves a continuous information representation, which can be seen in the working memory in the prefrontal cortex and columnar activity in the visual cortex. In the present study, we propose a neural network model that achieves discrete and continuous information representation. We use a statistical–mechanical analysis to find that a localized retrieval phase exists in the proposed model, where the memory pattern is retrieved in the localized subpopulation of the network. In the localized retrieval phase, the discrete and continuous information representation is achieved by using the orthogonality of the memory patterns and the neutral stability of fixed points along the positions of the localized retrieval. The obtained phase diagram suggests that the antiferromagnetic interaction and the external field are important for generating the localized retrieval phase.抄録全体を表示PDF形式でダウンロード (272K) -
Yoshihiro Morishita, Hiroshi Morita, Masao Doi2009 年 78 巻 11 号 p. 114802
発行日: 2009/11/15
公開日: 2011/12/28
ジャーナル 認証ありThe dynamics of adhesion and detachment between soft poly(dimethylsiloxane) (PDMS) sphere and glass substrate was studied experimentally. The force, contact radius and contact angle were measured when the PDMS sphere is pressed against and pulled off from the glass substrate with various loading speeds. It is shown that (1) the force can be predicted accurately by the extended JKR theory which uses the apparent surface energy wapp, (2) the apparent surface energy wapp depends only on the velocity of the contact line, and does not depend on the loading speed except during the period where the contact angle changes rapidly, and (3) the integral of the apparent surface energy with respect to the contact area in the adhesion-detachment cycle is approximately equal to the work done to the system by the load. These results indicate that the adhesion-detatchment dynamics of the PDMS sphere is essentially governed by the local energy dissipation caused by the motion of the contact line.抄録全体を表示PDF形式でダウンロード (604K) -
Yuo-Hsien Shiau2009 年 78 巻 11 号 p. 115001
発行日: 2009/11/15
公開日: 2011/12/28
ジャーナル 認証ありPDF形式でダウンロード (566K) -
Rebeca L. Ribeiro, Ismardo Bonalde, Yoshinori Haga, Rikio Settai, Yosh ...2009 年 78 巻 11 号 p. 115002
発行日: 2009/11/15
公開日: 2011/12/28
ジャーナル 認証ありPDF形式でダウンロード (325K) -
Taichi Terashima, Megumi Tomita, Motoi Kimata, Hidetaka Satsukawa, Ats ...2009 年 78 巻 11 号 p. 118001
発行日: 2009/11/15
公開日: 2011/12/28
ジャーナル 認証ありPDF形式でダウンロード (38K) -
Masahito Mochizuki, Nobuo Furukawa2009 年 78 巻 11 号 p. 118002
発行日: 2009/11/15
公開日: 2011/12/28
ジャーナル 認証ありPDF形式でダウンロード (477K)
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