Journal of the Physical Society of Japan
Online ISSN : 1347-4073
Print ISSN : 0031-9015
ISSN-L : 0031-9015
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Volume 61, Issue 2
Displaying 1-50 of 54 articles from this issue
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  • X-Ray Resonance Exchange Scattering at the Nd L2,3-Edges in Nd2Fe14B
    Akihisa Koizumi, Hiroshi Maruyama, Kazumichi Namikawa, Koichi Mori, Hi ...
    1992 Volume 61 Issue 2 Pages 399-402
    Published: February 15, 1992
    Released on J-STAGE: May 29, 2007
    DOIhttps://doi.org/10.1143/JPSJ.61.399
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    X-ray resonance exchange scattering has been measured at the Nd L2,3 absorption edges on the (440) Bragg reflection in a ferromagnetic Nd2Fe14B single crystal. The magnetic spectrum at the L2-edge reflects the spin polarization of unoccupied 5d-bands of Nd due to electric dipole transitions. The magnetic spectrum at the L3-edge shows a more complicated structure than that at the L2-edge. The difference in magnetic spectra between the L2- and L3-edges is discussed from the viewpoints of LS coupling in 5d-bands and the contributions of electric quadrupole transitions to the highly localized and partially vacant 4f-states.
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  • Log-Gamma Distribution Model of Intermittency in Turbulence
    Yoshio Saito
    1992 Volume 61 Issue 2 Pages 403-406
    Published: February 15, 1992
    Released on J-STAGE: June 01, 2007
    DOIhttps://doi.org/10.1143/JPSJ.61.403
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    A probability distribution for the logarithm of the breakdown coefficient εr⁄εl of energy dissipation density is shown, under the conditions of scale similarity, to be infinitely divisible, and the log-gamma distribution model of intermittency in fully developed turbulence is proposed. As a result, the intermittency exponent of the qth-order moment of the breakdown coefficient is derived to be μq=d {q−[ln (β⁄β+q)⁄ln (β⁄β+1)]}, where d denotes the space dimension, and β is a nondimensional parameter determined by the value of μ2 and d. The results derived from the model are in good agreement with those of experiments and a numerical simulation.
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  • Cascading Bifurcations to Chaos in a Current-Carrying Ion Sheath
    Mitsuo Kono, Hisatoshi Nakashima, Akio Komori
    1992 Volume 61 Issue 2 Pages 407-410
    Published: February 15, 1992
    Released on J-STAGE: June 01, 2007
    DOIhttps://doi.org/10.1143/JPSJ.61.407
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    A theory is developed to explain cascading bifurcations to chaos observed in a current-carrying ion sheath. The basic equation is derived to describe ion dynamics in an ion sheath which obeys the Child-Langmuir law for a large potential drop and is numerically solved to show the same bifurcation sequences as those in the experiments.
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  • Incoherent Inelastic Neutron Scattering from Hydrogen-Bonded Compound KH2PO4
    Kaoru Shibata, Susumu Ikeda
    1992 Volume 61 Issue 2 Pages 411-414
    Published: February 15, 1992
    Released on J-STAGE: June 01, 2007
    DOIhttps://doi.org/10.1143/JPSJ.61.411
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    The hydrogen vibrational modes in KH2PO4 (KDP) were, for the first time, clearly observed by incoherent inelastic neutron-scattering measurements over a wide energy range; some small changes in the spectra were found around the transition temperature. By single-crystal measurements of KDP, the bending and stretching modes of the H-atom could be assigned.
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  • Edge and Bulk Landau States in Quantum Hall Regime
    Tsuneya Ando
    1992 Volume 61 Issue 2 Pages 415-418
    Published: February 15, 1992
    Released on J-STAGE: June 01, 2007
    DOIhttps://doi.org/10.1143/JPSJ.61.415
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    Backscattering probability of edge states is calculated in two-dimensional systems confined within a finite width in strong magnetic fields. The critical exponent of localization length of bulk Landau states is derived using the system-size dependence of the energy interval where the transmission probability changes from zero to unity.
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  • Electronic States of Asymmetric Dimers at the Si(100)-(2×1) Surface in Electric Fields
    Kazuyuki Watanabe, Kazuto Watanabe
    1992 Volume 61 Issue 2 Pages 419-422
    Published: February 15, 1992
    Released on J-STAGE: May 29, 2007
    DOIhttps://doi.org/10.1143/JPSJ.61.419
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    Electronic structures of Si(100)-(2×1) in electric fields are calculated by the self-consistent pseudopotential method. Assuming an asymmetric dimer model, we obtain a characteristic change in the charge distribution around the dimer due to applied fields of 0.6 V/Å–1.8 V/Å. It is found that the field of negative tip voltage repels the electron charge around an up atom of the dimer and pushes it to the inside of the bulk, reducing the charge imbalance of the asymmetric dimer. This result is consistent with the recent scanning tunneling microscope (STM) experiment, which analyzed the relation between the buckling of dimers and applied fields.
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  • On Dimer Pairing Mechanism of Superconductivity
    Masatoshi Imada
    1992 Volume 61 Issue 2 Pages 423-427
    Published: February 15, 1992
    Released on J-STAGE: June 01, 2007
    DOIhttps://doi.org/10.1143/JPSJ.61.423
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    Physical properties in a dimer pairing superconductor are examined. The pairing has a finite net momentum and breaks lattice translational symmetry as well as the gauge symmetry. The mean field equations for the dimerized t-J model and the spin-Peierls t-J model are solved numerically to discuss novel features of the dimer pairing mechanism. The dynamical spin susceptibility is calculated to discuss spin excitations in the superconducting state. The energy gap opens over the Fermi surface without nodes, while the Hebel-Slichter peak is absent in the NMR relaxation rate.
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  • Nonlocal Unitary Transformation and String Order in S=1⁄2 Heisenberg Chain with Bond Alternation
    Satoshi Takada
    1992 Volume 61 Issue 2 Pages 428-432
    Published: February 15, 1992
    Released on J-STAGE: May 29, 2007
    DOIhttps://doi.org/10.1143/JPSJ.61.428
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    We investigate the ground-state properties of an S=1⁄2 Heisenberg chain with bond alternation, which reduces to the S=1 antiferromagnetic (AF) chain in a strong coupling limit, using a nonlocal unitary transformation. It is shown that the transformation works well, as in the case of S=1 AF models, and hence it transforms the model into a ferromagnetic model with a Z2×Z2 symmetry. The phase diagram is calculated in the transformed system with string order parameters by a molecular field approximation, and the result is shown to agree essentially with the numerical result obtained by Hida. We also argue the difference between Hida’s string order parameter and one corresponding to the S=1 string order parameter of den Nijs and Rommelse.
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  • Co Substitution Effect on the Electronic Structure of NiS Studied by X-Ray Photoemission Spectroscopy
    Takeshi Mamori, Masanori Matoba, Atsushi Fujimori, Shuichiro Anzai
    1992 Volume 61 Issue 2 Pages 433-436
    Published: February 15, 1992
    Released on J-STAGE: May 29, 2007
    DOIhttps://doi.org/10.1143/JPSJ.61.433
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    X-ray photoemission spectroscopy (XPS) measurements of the valence band, Ni 2p core level, Co 2p core level and S 2s, 2p core levels were carried out on the metallic state of Ni1−vCovS (0≤v≤0.06). The main peak of the valence band spectra shifts toward lower binding energy (EB) with increasing v (dEB⁄dv=−2.6±0.4 eV/mol). This behavior is different from those reported on vacancy introduction or on the Se substitution in Ni1−xS or NiS1−ySey (dEB⁄dx≈0; dEB⁄dy≈0). The Ni 2p3⁄2 core level peak also shifts toward lower EB (dEB⁄dv=−1.8±0.6 eV/mol), while no change in the S 2s or 2p core level peak is observed. We propose the possibility that the hybridization between the Co d7L and the Ni d8L peaks near the EF, where L denotes a ligand hole, leads to the modification of the electronic state of Ni sites in Ni1−vCovS.
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  • NMR and NQR Studies of a Semiconducting Compound U3Ni3Sb4
    Tetsuo Ohama, Hiroshi Yasuoka, Toshiro Takabatake, Shun-ichi Miyata, H ...
    1992 Volume 61 Issue 2 Pages 437-440
    Published: February 15, 1992
    Released on J-STAGE: June 01, 2007
    DOIhttps://doi.org/10.1143/JPSJ.61.437
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    The 121Sb Knight shift and the 121,123Sb nuclear spin-lattice relaxation time T1 in U3Ni3Sb4 have been measured. In the temperature range between 25 and 250 K, 1⁄T1, which has been measured by nuclear quadrupole resonance (NQR), follows an activation law with an activation energy of 21.1 meV. The relaxation process is dominated by the magnetic contribution. The Knight shift is represented as the sum of a strongly temperature-dependent anisotropic term and a temperature-independent term. The transferred hyperfine field from the U 5f electrons through the U 5f-Sb 5p hybridization makes an important contribution to the Knight shift.
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  • Temperature Dependence of NMR Spectrum at Cu(2) Site in Antiferromagnetic YBa2Cu3O6.1
    Y\={u}ji Iwamoto, Masahiro Matsumura, Hideki Yamagata, Kenji Ishida, Y ...
    1992 Volume 61 Issue 2 Pages 441-444
    Published: February 15, 1992
    Released on J-STAGE: May 29, 2007
    DOIhttps://doi.org/10.1143/JPSJ.61.441
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    The temperature dependence of the NMR spectrum at the Cu(2) site in antiferromagnetic YBa2Cu3O6.1 was observed from 1.5 K to 77 K, well below the Néel temperature, in which the nuclear Zeeman and quadrupole frequencies, νL and νQ, were deduced. The frequency νL(T) follows well the relation (νL(0)−νL(T))⁄νL(0)=ATα above 10 K. The parameter values are evaluated as α=1.87, A=6.83×10−6 (K−α) and νL(0)=89.80 (MHz). The fact that the exponent α is close to 2 suggests the presence of gapless spin wave excitations. The coefficient A is two orders of magnitude larger than the value roughly estimated from the result of the neutron scattering experiment, which suggests the presence of larger low-energy excitations in the spin wave spectrum.
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  • Free-Exciton Luminescence and Weak-Exciton Scattering in Coronene Crystals
    Maki Sakurai, Mitsuhiro Furukawa, Ken-ichi Mizuno, Atsuo Matsui
    1992 Volume 61 Issue 2 Pages 445-448
    Published: February 15, 1992
    Released on J-STAGE: May 29, 2007
    DOIhttps://doi.org/10.1143/JPSJ.61.445
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    Luminescence and absorption spectra of coronene single crystals are studied. Free-exciton luminescence is observed for the first time. The intensity of free-exciton luminescence decreases with decreasing temperature, suggesting that free excitons are in thermal equilibrium with excitons in a relaxed state which is located 1070 cm−1 below the bottom of the free-exciton band. The line shape of the O–O absorption band which is located at 23220 cm−1 at 10.4 K is Lorentzian, indicating that scattering of excitons by phonons is weak.
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  • Complementary Roles of Co 2p X-Ray Absorption and Photoemission Spectra in CoO
    Kozo Okada, Akio Kotani
    1992 Volume 61 Issue 2 Pages 449-453
    Published: February 15, 1992
    Released on J-STAGE: May 29, 2007
    DOIhttps://doi.org/10.1143/JPSJ.61.449
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    We investigate the Co 2p core-level X-ray absorption (XAS) and photoemission spectra (XPS) in CoO on the basis of a CoO6 cluster model, where Co 3d-O 2p hybridization and multiplet coupling are fully taken into account. We pay particular attention to the effects of multiplet coupling on the XPS and those of Co 3d-O 2p hybridization on the XAS, because those points have been disregarded in the analyses made so far by many authors. From the combined analysis, we show that the XPS and XAS provide us with complementary information on the electronic states of CoO.
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  • Inverse Scattering of a Medium Which Supports M-Types of Wave
    Ning Wang, Sadayuki Ueha
    1992 Volume 61 Issue 2 Pages 455-461
    Published: February 15, 1992
    Released on J-STAGE: June 01, 2007
    DOIhttps://doi.org/10.1143/JPSJ.61.455
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    The inverse scattering transform of Equation V+z(ω, z)=(jωΛ(z)+Δ)V(ω, z) where V(ω, z) is an 2M-element column vector and Δ(z) is a off-diagonal matrix, is considered. A set of scattering data is given and the problem of restructing Δ(z) from this scattering data is sloved. An application for inverse scattering of elastic P–SV wave is given.
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  • Higher Spin Cyclic Solid-on-Solid Models
    Taichiro Takagi, Tetsuo Deguchi, Miki Wadati
    1992 Volume 61 Issue 2 Pages 462-469
    Published: February 15, 1992
    Released on J-STAGE: June 01, 2007
    DOIhttps://doi.org/10.1143/JPSJ.61.462
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    We discuss construction of fusion models of the cyclic solid-on-solid model. We have explicitly shown conditions for the existence of non-zero Boltzmann weights. In addition, the free energy of the fusion model is calculated in a regime.
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  • Diagrammatical Techniques for Two-Dimensional Ising Models. I
    Tohru Morita
    1992 Volume 61 Issue 2 Pages 470-476
    Published: February 15, 1992
    Released on J-STAGE: June 01, 2007
    DOIhttps://doi.org/10.1143/JPSJ.61.470
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    Techniques of division of a lattice site and integration of lattice sites are proposed in the diagrammatical method for the two-dimensional Ising model. It is shown that the calculations for systems on various lattices are reduced to those for a system on a square lattice, with the aid of the techniques. The technique of integration, in particular, is always useful for the Ising model on the dual lattice, when the consideration of the free fermion model is useful.
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  • Equilibrium Crystal Shape of Planar Ising Antiferromagnets in External Fields
    Noriko Akutsu
    1992 Volume 61 Issue 2 Pages 477-498
    Published: February 15, 1992
    Released on J-STAGE: June 01, 2007
    DOIhttps://doi.org/10.1143/JPSJ.61.477
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    For square and honeycomb Ising antiferromagnets (AF) in external fields, one-dimensional (1D) anisotropic interface tension and a 2D equilibrium crystal shape (ECS) are calculated with high precision by a method using the free random walk with imaginary path-weights. The field dependence of interface entropy and interface stiffness are also shown. We apply the results to the stoichiometrically two components crystals of GaAs type. The relative vapor pressure dependence of anisotropic step tension and facet shape of the 3D ECS are obtained.
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  • Quark Jet Model Study of Forward and Backward Multiplicities in νp and \barνp Interactions
    Noboru Hashimoto
    1992 Volume 61 Issue 2 Pages 499-505
    Published: February 15, 1992
    Released on J-STAGE: June 01, 2007
    DOIhttps://doi.org/10.1143/JPSJ.61.499
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    Based on the quark jet model we calculate the forward and backward multiplicities in νp and \barνp interactions. In these calculations the observed rapidity distributions of particles produced in e+e− annihilations are used as input data to determine the rapidity distribution of secondary particles in the quark jet. The model describes the ν(\barν)p forward and backward multiplicities successfully, if we choose the inelasticity parameter η to be 0.46. This result suggests that the inelasticity parameter takes different values for leptonic and hadronic interactions.
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  • Box Correction in e+e−→Θ(1−−t\bart)→μ+μ−
    Yoshio Yamashita, Masataka Igarashi
    1992 Volume 61 Issue 2 Pages 506-513
    Published: February 15, 1992
    Released on J-STAGE: June 01, 2007
    DOIhttps://doi.org/10.1143/JPSJ.61.506
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    The lowest order box correction to e+e−→Θ(1−−t\bart)→μ+μ− is estimated by using the model of the vector coupling to photon proposed by Kroll, Lee and Zumino. The box correction is found to be mass-dependent in appearance and even amounts to several % for the toponium.
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  • High-Pressure Raman Study of Sulfur Hexafluoride up to 10 GPa
    Shigeo Sasaki, Yasuyuki Tomida, Hiroyasu Shimizu
    1992 Volume 61 Issue 2 Pages 514-518
    Published: February 15, 1992
    Released on J-STAGE: May 29, 2007
    DOIhttps://doi.org/10.1143/JPSJ.61.514
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    High-pressure Raman spectra of sulfur hexafluoride (SF6) have been measured up to 10 GPa at 300 K in a gasketed diamond anvil cell. The pressure dependence of three Raman active intramolecular vibrations and the overtone of the ν6 mode has been investigated. The liquid-solid I and solid I–II phase transitions at respective pressures 0.25 GPa and 1.80 GPa are presented by the drastic change in Raman band widths and the splitting of vibrational modes, respectively. The observed solid I and II phases correspond to plastic (bcc structure) and monoclinic phases, respectively, that also appear at low temperatures under atmospheric pressure. The I–II transition pressure is supported by the good agreement with that obtained by extrapolation (to 300 K) of phase boundary previously determined at low temperatures.
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  • Cross Sections for Excitation and De-Excitation Processes among 3P2, 3P1, 3P0, 1D2 and 1S0 of Ne2+ and Ar2+ in Collisions with Rare Gases
    Atsushi Fukuroda, Nobuo Kobayashi, Yozaburo Kaneko
    1992 Volume 61 Issue 2 Pages 519-523
    Published: February 15, 1992
    Released on J-STAGE: May 29, 2007
    DOIhttps://doi.org/10.1143/JPSJ.61.519
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    Cross sections for excitation and de-excitation in Ne2+ and Ar2+ have been measured with a high resolution translational energy spectrometer. For Ar2+, the cross sections for the transitions 3P2↔3P1, 3P2↔1D2 and 1D2↔1S0 have been measured in collisions with He and Ne in the energy range from 0.8 to 5 keV. For Ne2+, no peak due to the transitions has been observed.
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  • Boltzmann Equation Analysis of Electron Swarm Development in Model Gases with Power-Law Elastic Scattering
    Hidenori Itoh, Masaru Kawaguchi, Yoshitaka Nakao, Hiroaki Tagashira
    1992 Volume 61 Issue 2 Pages 524-529
    Published: February 15, 1992
    Released on J-STAGE: May 29, 2007
    DOIhttps://doi.org/10.1143/JPSJ.61.524
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    The electron swarm behaviors in model gases with elastic momentum transfer cross-section of the form q(ε)∝εr (r=−1⁄2, 0, 1/2 and 1) are analyzed by the time-of-flight method of a Boltzmann equation. The velocity distribution functions are apprroximated by three term expansion. Here ε is the electron energy. The ratios DL⁄DT are calculated to study an anisotropy in real space. Here DL and DT are the longitudinal and the transverse diffusion coefficients to an electric field E. The values of electron-to-atom mass ratios m⁄M are changed from 10−4 to 5×10−2 and the values of E⁄N are taken as 2.8, 14 and 28 Td respectively. Here N is the gas number density. The present result shows that the anisotropy in real space depends upon m⁄M regardless of E⁄N. The discrepancy between the electron diffusion coefficient DV as defined in velocity space and DT, and the validity of the usual two-term method to calculate the time-of-flight parameters are discussed in detail.
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  • Monte Carlo Studies of Transport in a Reversed Field Pinch
    T. S. Chen, Akiyoshi Nagata, Koichi Sato, Hisao Ashida, Tsuneo Amano
    1992 Volume 61 Issue 2 Pages 530-541
    Published: February 15, 1992
    Released on J-STAGE: June 01, 2007
    DOIhttps://doi.org/10.1143/JPSJ.61.530
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    Transport in a realistic reversed field pinch (RFP) configuration is studied numerically for neoclassical and MHD fluctuation transport mechanisms, by Monte Carlo simulation. The results indicate that neoclassical transport due to guiding center drift is one or two orders lower than classical transport due to finite gyro-motion and thus is not important for RFP plasmas. However, the electron diffusion coefficient corresponding to a typical MHD fluctuation configuration of the magnetic Reynolds number S=104, and equilibrium β=8% is about 106 cm2/sec which is two orders higher than the classical transport, and thus is an important transport loss mechanism for RFP plasma confinement.
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  • Electrostatic Potential in the Endcells of a Tandem Mirror under Electron Cyclotron Resonance Heating
    Isao Katanuma, Yasuhito Kiwamoto, Haruichi Washimi, Kameo Ishii, Kiyos ...
    1992 Volume 61 Issue 2 Pages 542-559
    Published: February 15, 1992
    Released on J-STAGE: June 01, 2007
    DOIhttps://doi.org/10.1143/JPSJ.61.542
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    The electrostatic potential profile in the endcells of a tandem mirror under electron cyclotron resonance heating is studied by including an ionization process. A plug potential is found to form with a combination of created ions by ionization, wave-heated electrostatically trapped electrons and mirror trapped electrons, but without a help of high energy sloshing ions. In the present model the electrostatic potential has its maximum at the outer mirror throat of end mirror cell.
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  • Simulation of High Ion Temperature Mode in JT-60
    Katsuhiro Shimizu, Nobuyuki Hosogane, Hiroshi Shirai, Toshio Hirayama
    1992 Volume 61 Issue 2 Pages 560-567
    Published: February 15, 1992
    Released on J-STAGE: June 01, 2007
    DOIhttps://doi.org/10.1143/JPSJ.61.560
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    The high ion temperature mode in JT-60, where Ti above 10 keV were obtained by hydrogen beam heating of 20 MW into hydrogen limiter plasmas with Ip=1∼2 MA, is investigated by using the one dimensional transport code and experimental data of electron density and temperature. It is found that, in a low density plasma with high Zeff, the dilution of thermal ions due to impurities and fast ions produced by neutral beam injection causes rapid increase in the ion temperature. On the other hand, in the steady state, the dilution has little effect on the central ion temperature for fixed electron temperature because the convection loss is dominant.
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  • Solitary and Shock Structures Induced by Poloidal Flow in Tokamaks
    Tosiya Taniuti, Hirofumi Moriguchi, Yasutomo Ishii, Kiyomasa Watanabe, ...
    1992 Volume 61 Issue 2 Pages 568-586
    Published: February 15, 1992
    Released on J-STAGE: June 01, 2007
    DOIhttps://doi.org/10.1143/JPSJ.61.568
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    It is shown that solitary and shock structures can appear in tokamaks, when a poloidal flow velocity becomes close to εcs, where cs is a sound velocity and ε is a small inverse aspect ratio. To describe asymptotic behavior of the flow velocity vp, a KdV (Korteweg de Vries)-Burgers equation with a sinusoidal force term is derived from the two-fluid MHD equations with small resistivity and parallel viscosity. A solitary flow velocity structure appears inside of the torus (at the poloidal angle θ=π) in the non-dissipative, dispersive case. The supersonic flow (vp>εcs) parallel to the poloidal magnetic field and the subsonic anti-parallel flow (vp<εcs) are stable. In both cases the solitary density perturbation is negative. For the non-dispersive, dissipative case or the one-fluid MHD limit the forced Burgers equation becomes appropriate to describe the flow dynamics. This case corresponds to an appearance of shock structure. By solving an initial value problem it is shown that the shock position moves from θ\simeq0 to θ\simeqπ with the variation of |vp−εcs|.
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  • Elastic Properties and Thermal Expansion of NaNO3 Single Crystal
    Yoshio Takeuchi, Yukihiko Sasaki
    1992 Volume 61 Issue 2 Pages 587-595
    Published: February 15, 1992
    Released on J-STAGE: June 01, 2007
    DOIhttps://doi.org/10.1143/JPSJ.61.587
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    All components of elastic stiffness and compliance in NaNO3 crystal have been determined from room temperature to 300°C. They show anomalies associated with the phase transition in the vicinity of Tc. Thermal expansion coefficients parallel and perpendicular to the three-fold axis exhibit λ-type temperature dependence near Tc. The phase transition of NaNO3 is discussed on the basis of a phenomenological theory with an order parameter related to an irreducible representation at k8 point of D3d5.
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  • Thermoelectric Power of Graphite Intercalation Compounds with Iodine Monochrolide
    Koji Kobayashi, Hisashi Oshima, Ko Sugihara, Takuro Tsuzuku
    1992 Volume 61 Issue 2 Pages 596-601
    Published: February 15, 1992
    Released on J-STAGE: June 01, 2007
    DOIhttps://doi.org/10.1143/JPSJ.61.596
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    Thermoelectric power (TEP) of iodine monochrolide-graphite intercalation compounds (ICl–GICs) exhibits a linear temperature dependence at low temperatures, which is ascribed to the diffusion term. Above 200 K TEP levels off. This behavior stems from the phonon drag effect. By choosing an appropriate parameter set Sugihara’s theory can provide a good fit with the observed TEP results for the stage-1 and -2 ICl–GICs.
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  • Calculated Fermi Surface of YCu2 by LAPW Method
    Hisatomo Harima, Akira Yanase
    1992 Volume 61 Issue 2 Pages 602-608
    Published: February 15, 1992
    Released on J-STAGE: May 29, 2007
    DOIhttps://doi.org/10.1143/JPSJ.61.602
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    We report the electronic structure calculation and Fermi surfaces of orthorhombic YCu2 using an LAPW method within the local density approximation. YCu2 is a non-f reference material of a dense Kondo compound CeCu2. Calculated Fermi surfaces of YCu2 are multiply connected being consistent with the magnetoresistance measurements. Calculated extremal areas explain the origins of many experimental dHvA signals.
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  • Acoustic de Haas-van Alphen Effect of YCu2 and CeCu2
    Rikio Settai, Terutaka Goto, Yoshichika \={O}nuki
    1992 Volume 61 Issue 2 Pages 609-615
    Published: February 15, 1992
    Released on J-STAGE: May 29, 2007
    DOIhttps://doi.org/10.1143/JPSJ.61.609
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    Acoustic de Haas-van Alphen (dHvA) effect of the rare earth intermetallic compounds YCu2 and CeCu2 with the orthorhombic structure has been investigated by the sound velocity measurement. The field angle dependence of the dHvA frequency of YCu2 in the present acoustic method reproduced the previous result of the magnetic susceptibility measurement. Furthermore, a few new branches below 5×106 Oe were also found. The characteristic features of the oscillatory intensity of the transverse modes in YCu2 are presented in the relation with the origin of the elastic softening in the C44 and C66 modes. The correspondence to the band calculation of YCu2 by Harima and Yanase is discussed. Some aspects of the oscillatory behavior associated with the metamagnetic transition in CeCu2 are also presented.
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  • Soft X-Ray Spectroscopic Analysis of Ni-Silicides
    Hatsuo Nakamura, Masaaki Hirai, Masahiko Kusaka, Motohiro Iwami, Hirok ...
    1992 Volume 61 Issue 2 Pages 616-620
    Published: February 15, 1992
    Released on J-STAGE: May 29, 2007
    DOIhttps://doi.org/10.1143/JPSJ.61.616
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    The valence-band electronic structure of Ni-silicide system, NiSi2, NiSi and Ni2Si, has been studied by measuring soft X-ray Si L2,3 emission spectra. It is found that the Si L2,3 spectra show very different spectral features among these three silicides. The spectra of silicides are compared with the theoretical density of states and discussion is given on the electronic structure of these silicides. It is suggested that Si s electronic state contributes significantly to the upper part of valence-band of the three silicide systems.
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  • Gauge Fields in Slave-Fermion Formalism. I. Destruction of the Néel Order
    Kazuhiro Kuboki, Daijiro Yoshioka
    1992 Volume 61 Issue 2 Pages 621-630
    Published: February 15, 1992
    Released on J-STAGE: June 01, 2007
    DOIhttps://doi.org/10.1143/JPSJ.61.621
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    The t′-J model (t′: transfer integral between next nearest neighbor sites) on a square lattice is studied within the slave-fermion formalism. In a mean-field approximation the antiferromagnetic long-range order (AFLRO), which is represented by the Bose condensation of the spinon at T=0, persists even for large doping rate. It is shown that the gauge field representing the fluctuations around the mean-field solution works in reducing the AFLRO, making the phase diagram of the ground state closer to that observed experimentally.
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  • Meissner Effect Due to Cooper Pairs between Bloch Electrons: Analysis of Penetration Depth of YBa2Cu3O7
    Fusayoshi J. Ohkawa
    1992 Volume 61 Issue 2 Pages 631-638
    Published: February 15, 1992
    Released on J-STAGE: June 01, 2007
    DOIhttps://doi.org/10.1143/JPSJ.61.631
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    A theory of the Meissner effect due to Cooper pairs between Bloch electrons is presented in the gauge-invariant form by including effects of strong electron correlation. The theory is applied to analyzing observed penetration depth λ(T) of YBa2Cu3O7 with Tc≈90 K. Observed λ(0)≈1400 Å can be explained, if the effective mass of quasiparticles is about ten times as large as the electron mass. By assuming that the superconducting gap is as large as 2εG⁄Tc≈8, as implied by many experiments, it is shown that anisotropic Cooper pairs between heavy electrons in the Mott-transition region can explain the observed λ(T) above 35 K. One of the possible scenarios to explain the data below 35 K is a successive superconducting transition at Tc2≈35 K, as implied by small but sharp anomalies in the transverse nuclear quadrupole relaxation rate. It is argued that the complete gap is open below Tc2≈35 K.
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  • Second Superconducting Transition Driven by Charge Density Wave
    Fusayoshi J. Ohkawa
    1992 Volume 61 Issue 2 Pages 639-648
    Published: February 15, 1992
    Released on J-STAGE: June 01, 2007
    DOIhttps://doi.org/10.1143/JPSJ.61.639
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    Instability of charge density wave can drive successive superconducting transitions. The transition at a lower temperature can be detected by the softening of phonons, whose symmetry is compatible with the symmetry of the product of the two superconducting order parameters. It is argued that the second transition is responsible for tiny anomalies around Tc2≈35 K in high-temperature superconductors YBa2Cu3O7 with superconducting critical temperature Tc≈90 K. It is also argued that the anisotropic Cooper pairing is responsible for high-temperature superconductivity not only in YBa2Cu3O7 but also in the other cuprate oxides.
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  • Charge Fluctuation and Superconductivity in the d-p Model
    Dai S. Hirashima, Yoshiaki \={O}no, Tamifusa Matsuura, Yoshihiro Kurod ...
    1992 Volume 61 Issue 2 Pages 649-665
    Published: February 15, 1992
    Released on J-STAGE: June 01, 2007
    DOIhttps://doi.org/10.1143/JPSJ.61.649
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    We investigate effects of the repulsive interaction Upd between holes on the nearest-neighbor Cu- and O-sites in the d-p model with infinite repulsion on the Cu site using the auxiliary boson technique and the 1⁄N expansion method. It is found that the condition for a metal-insulator (M-I) transition to occur at the half-filled case is modified. We then investigate the charge susceptibility; it is found that the thermodynamic charge susceptibility is enhanced by Upd except for the region around the critical point of the M-I transition. It is found to diverge at a certain value of Upd, which implies an instability toward a phase separation. On the basis of these calculations, we obtain phase diagrams, which consist of the metallic, unstable (phase-separating) and insulating phases. Furthermore, we calculate the quasiparticle interaction and find that the charge fluctuation induces attractive interaction comparable in magnitude to the repulsive interaction originating from the on-site repulsion Ud in both of the s- and d-wave channel; in the immediate vicinity of the instability, the attraction can overcome the repulsion.
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  • In Situ Absorption Spectra and ESR Measurements of Poly(trans-(2,2′-bithiophene-5-yl)-(2,2′:5′,2″-terthiophene-5-yl)ethylene) During Electrochemical Doping
    Toshinori Iwasa, Tsuyoshi Kawai, Mitsuyoshi Onoda, Juzo Nakayama, Hiro ...
    1992 Volume 61 Issue 2 Pages 666-673
    Published: February 15, 1992
    Released on J-STAGE: June 01, 2007
    DOIhttps://doi.org/10.1143/JPSJ.61.666
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    The electrochemical, optical and magnetic properties of poly(trans-(2,2′-bithiophene-5-yl)-(2,2′:5′,2″-terthiophene-5-yl)ethylene), PBTTTE, during electrochemical p-type doping have been investigated in comparison with those of poly(trans-bis(thiophene-2-yl)ethylene), trans-PTE, by cyclic voltammetry, in situ optical absorption spectra, and electron spin resonance (ESR) measurements. The band gap energy of PBTTTE was evaluated to be 2.0 eV and about 0.1 eV larger than that of trans-PTE. This result can be interpreted in terms of a change in the torsion angle between neighboring thiophene rings. The spin susceptibility determied by ESR measurements increased from 2.4×10−8 to 4.4×10−6 emu/mol upon doping and then decreased slightly. Changes in optical absorption spectra and ESR spectra suggest the formation of polaron and/or bipolaron upon doping. The spin density evaluated from the spin susceptibility was inconsistent with the dopant density. That is, even at lightly doped state the newly developed species turn into p-type spinless bipolarons.
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  • Electrical Resistivity of Ti0.862Al0.102V0.036 Alloy between 4 and 1000 K
    S. J. Tzeng, J. J. Lin, Y. D. Yao, Y. Y. Chen
    1992 Volume 61 Issue 2 Pages 674-678
    Published: February 15, 1992
    Released on J-STAGE: June 01, 2007
    DOIhttps://doi.org/10.1143/JPSJ.61.674
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    We have measured the electrical resistivity ρ of a Ti0.862Al0.102V0.036 alloy in the temperature range 4–1000 K. At temperatures above about 500 K, a saturation behavior of ρ is observed and is ascribed to the breakdown of the Ioffe-Regel criterion. In addition, we observe a considerably weakened temperature dependence of the electron-phonon coupling in the range ≈100–1000 K, compared with that in good metals.
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  • Electrical Resistivity in Oxide Semiconductor BaBi1−xMoxO3
    Ikuyo Shiozaki, Hiroshi Watanabe, Atsushi Hattori
    1992 Volume 61 Issue 2 Pages 679-683
    Published: February 15, 1992
    Released on J-STAGE: May 29, 2007
    DOIhttps://doi.org/10.1143/JPSJ.61.679
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    Single crystals of BaBi1−xMoxO3 were grown with x up to 0.15. The electrical resistivity showed an activation type temperature dependence. The activation energy at room temperature increases from 0.1 to 0.24 (eV) with increasing x to 0.15. Near 0.05 of x transition from monoclinic to orthorhombic structures was observed. The corresponding change in the resistivity was observed in the range of 0.03<x<0.05. The activation energy increases when the crystal symmetry increases with increasing temperature, or with increasing molybdenum concentration. Such results rule out the picture of CDW-gap semiconductor. Instead we suggest the existence of localization gap at the Fermi surface, which comes from the disorder of Bi3+ and Bi5+, from impurities, or from oxygen vacancies.
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  • Superconductivity in Th3Ni3Sn4
    Yuji Aoki, Takashi Suzuki, Toshizo Fujita, Toshiro Takabatake, Shun-ic ...
    1992 Volume 61 Issue 2 Pages 684-691
    Published: February 15, 1992
    Released on J-STAGE: June 01, 2007
    DOIhttps://doi.org/10.1143/JPSJ.61.684
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    Specific heat, resistivity and ac- and dc-magnetic susceptibility measurements revealed that Th3Ni3Sn4 is a new superconductor with the transition temperature Tc=1.38 K. The electronic specific heat coefficient γ is 31.1 mJ/K2 mol-f.u., the Debye temperature ΘD is 255 K and the electron-phonon coupling constant λep is 0.43. The upper critical field Hc2 determined by ac-susceptibility in magnetic fields follows the temperature dependence calculated by Helfand and Werthamer. We conclude that Th3Ni3Sn4 is a BCS-superconductor of type-II with the GL parameter κ=10. Both susceptibility enhancement probably due to spin fluctuation and anomalous temperature dependence of the resistivity suggest that the conduction electrons with d-character play an essential role in the superconductivity.
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  • Comment on the de Haas-van Alphen Effect in the Superconducting Mixed State of 2H-NbSe2
    Yoshichika \={O}nuki, Izuru Umehara, Takao Ebihara, Nobuyuki Nagai, K& ...
    1992 Volume 61 Issue 2 Pages 692-695
    Published: February 15, 1992
    Released on J-STAGE: June 01, 2007
    DOIhttps://doi.org/10.1143/JPSJ.61.692
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    We present the de Haas-van Alphen (dHvA) effect in the superconducting mixed state of 2H-NbSe2. Our data are consistent with the dHvA results obtained by Graebner and Robbins, which have been the subject of controversy from the viewpoint of experiment and theory. We discuss the reason why the theoretically expected cylindrical Fermi surfaces are not detected in the dHvA experiment and also the mechanism of the dHvA effect in the mixed state.
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  • NMR and Specific Heat Investigations in a Strong Electron-Phonon Coupling Superconductor HfV2*
    Yutaka Kishimoto, Naoya Shibata, Takashi Ohno, Yoshio Kitaoka, Kunisuk ...
    1992 Volume 61 Issue 2 Pages 696-703
    Published: February 15, 1992
    Released on J-STAGE: June 01, 2007
    DOIhttps://doi.org/10.1143/JPSJ.61.696
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    The nuclear spin lattice relaxation rate 1⁄T1 of 51V and specific heat have been measured in a strong electron-phonon coupling superconductor HfV2. The behavior of 1⁄T1T between 9.4 K and 100 K in the normal state can be attributed to a sharp narrow d-band with the half width of about 100 K. In the superconducting state, the 1⁄T1 shows a very small enhancement just below Tc and has the T5 dependence well below Tc. These behaviors are interpreted satisfactorily in terms of the ABM model. The value of the electronic specific heat coefficient is about forty times as large as that for Al. The electronic part of the specific heat is proportional to T3 at low temperatures. These facts mean that the superconducting energy gap of HfV2 is anisotropic and vanishes at points on the Fermi surface.
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  • Spherical Symmetric Spin Wave Theory of Heisenberg Model
    A. F. Barabanov, O. A. Starykh
    1992 Volume 61 Issue 2 Pages 704-708
    Published: February 15, 1992
    Released on J-STAGE: June 01, 2007
    DOIhttps://doi.org/10.1143/JPSJ.61.704
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    We represent simple decoupling scheme for two-time spin Green’s function which leads to the rotational invariant spin wave theory for low dimensional Heisenberg magnetics without broken symmetry and with correct sum rule \hatSr2=S(S+1). For two-dimensional S=1⁄2 antiferromagnet this theory predicts disodered ground state while for S>1⁄2 it possesses long range order at T=0. The dynamic structure factor is calculated.
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  • Band Calculations for MnZn and MnHg Fixing Local Spin Directions
    Shinpei Fujii, Shoji Ishida, Setsuro Asano
    1992 Volume 61 Issue 2 Pages 709-713
    Published: February 15, 1992
    Released on J-STAGE: May 29, 2007
    DOIhttps://doi.org/10.1143/JPSJ.61.709
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    Both of the compounds of MnZn and MnHg have a cubic structure of CsCl type, while the proposed spin alignments are different each other: non-collinear and collinear ones for MnZn and MnHg, respectively. To investigate the mechanism that produces the different spin alignments, total-energy band calculations have been performed by the use of an exchange-correlation potentital that depends on each of local spin directions at atomic spheres. Our calculations give the results consistent with experiment, and suggest that the hybridization between majority- and minority-spin states of the Mn-atom d band benefits the non-collinear alignment.
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  • 35Cl Nuclear Quadrupole Resonance in Tantalum Pentachloride
    Noriaki Okubo, Yoshihito Abe
    1992 Volume 61 Issue 2 Pages 714-721
    Published: February 15, 1992
    Released on J-STAGE: May 29, 2007
    DOIhttps://doi.org/10.1143/JPSJ.61.714
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    35Cl NQR spectrum and its temperature dependence in tantalum pentachloride are reported and compared with those in the related compounds. The temperature dependence is discussed in detail in relation with π-bond character.
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  • Low-Field NMR Line Shape Due to Anisotropic Local Fields
    Yoshio Aoyama, Motoyuki Tanaka
    1992 Volume 61 Issue 2 Pages 722-726
    Published: February 15, 1992
    Released on J-STAGE: June 01, 2007
    DOIhttps://doi.org/10.1143/JPSJ.61.722
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    The NMR line shape in a weak external field is investigated for the nuclear spin system with anisotropic distribution of the local magnetic fields by extending the Kubo-Toyabe model. It is shown that the line shape for a highly anisotropic system exhibits characteristic features and the peak position of the main line deviates considerably from the Larmor frequency of the applied field. A brief comment is also given on the line shape of the rotary resonance examined previously by Redfield, which may be useful to investigate the low-field NMR line shape.
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  • Transformation of Phonon Mode Behaviour in the AgClxBr1−x System
    Shoji Mimotogi, Taizo Masumi
    1992 Volume 61 Issue 2 Pages 727-734
    Published: February 15, 1992
    Released on J-STAGE: May 29, 2007
    DOIhttps://doi.org/10.1143/JPSJ.61.727
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    Systematic studies of far infrared reflection spectra and photoluminescence spectra of free excitons have been performed in AgClxBr1−x mixed crystals at low temperatures in the composition range x=0 to 1 and between x=0.10 and 0.39, respectively. Reflection spectra exhibit the existence of two TO-phonon modes for 0.03≤x≤0.50, whereas only one TO-phonon mode is recognized for x>0.87. Variation of reflection bands with the composition x indicates the transformation of phonon mode behaviour from the two-mode type to the one-mode type with increasing x. Photoluminescence spectra also exhibit the existence of two LO-phonon modes in AgBr-rich crystals, 0.12≤x≤0.27.
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  • Pattern Formation of Synaptic Connections in a Generalized Hebb-Type Learning Model
    Yoshiyuki Usami
    1992 Volume 61 Issue 2 Pages 735-743
    Published: February 15, 1992
    Released on J-STAGE: June 01, 2007
    DOIhttps://doi.org/10.1143/JPSJ.61.735
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    On the basis of a generalized Hebb-type learning model we discuss pattern formation of synapses in neural network system. We propose a generalized Hebb-type learning equation in which connection weight of synapse has an arbitrary potential function. Especially much attention is paid for the case where potential has double stable points. Computer simulation is performed upon this model and it is found that this neural network model has a merit that system keeps learned patterns after input signals are stopped. The correspondence of our model with physiological observations is discussed.
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  • Hidden Symmetry of Relativistic Particles
    Takayuki Hori
    1992 Volume 61 Issue 2 Pages 744-745
    Published: February 15, 1992
    Released on J-STAGE: June 01, 2007
    DOIhttps://doi.org/10.1143/JPSJ.61.744
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  • Monopole Drift-Wave Vortices in a Nonuniform Electric Field
    Koichi Saeki
    1992 Volume 61 Issue 2 Pages 746-747
    Published: February 15, 1992
    Released on J-STAGE: June 01, 2007
    DOIhttps://doi.org/10.1143/JPSJ.61.746
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  • Phase Diagram of CuBrTe–CuXTe (X=Cl, I) System
    Takashi Sakuma, Tadahiro Kaneko, Haruyuki Takahashi, K\={o}ji Honma
    1992 Volume 61 Issue 2 Pages 748-749
    Published: February 15, 1992
    Released on J-STAGE: May 29, 2007
    DOIhttps://doi.org/10.1143/JPSJ.61.748
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