Journal of the Physical Society of Japan
Online ISSN : 1347-4073
Print ISSN : 0031-9015
ISSN-L : 0031-9015
Volume 68, Issue 5
Displaying 1-50 of 54 articles from this issue
  • Hidetsugu Sakaguchi
    Subject area: Statistical physics and thermodynamics.
    1999 Volume 68 Issue 5 Pages 1465-1468
    Published: May 01, 1999
    Released on J-STAGE: October 01, 1999
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    A nonequilibrium state is studied by a Langevin equation with an additional boundary condition. The active transport across the membrane is studied as an example of a nonequilibrium state. The electric potential is normally positive outside the cell membrane owing to the active transport of ions. A probabilistic boundary condition plays a role of pumping for ions in the Langevin simulation.The mathematical model can be solved using an averaged Fokker-Planckequation, and the solution is compared with the Langevin simulation.
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  • Hiroyuki Fujishiro, Tetsuo Fukase, Manabu Ikebe, Tsutomu Kikuchi
    Subject area: Mechanical and acoustical properties of condesed matter.
    1999 Volume 68 Issue 5 Pages 1469-1472
    Published: May 01, 1999
    Released on J-STAGE: October 01, 1999
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    The sound velocity vs(T) of La1-XCaXMnO3 (0.08≤ X≤ 0.30) has been measured and two types of vs(T) anomalies have been observed. One is the vs(T) minimum around the ferromagnetic transition temperature Tc, and the other is the vs(T) upturn below the characteristic temperature T* which is lower than Tc. T*, as a function of the Ca concentration X, shows a maximum at about X=1/8 and may be related to the onset of the charge-ordered phase similar to the vs(T) anomalies in La1-XSrXMnO3.
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  • Mamoru Yamashita, Syozo Takeno
    Subject area: Equations of state, phase equilibria, and phase transitions.
    1999 Volume 68 Issue 5 Pages 1473-1476
    Published: May 01, 1999
    Released on J-STAGE: October 01, 1999
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    The ground state of the XY model with competing interaction, which is reduced to the axial next nearest neighbour Ising model at a limit of infinite value of strength of twofold field, is studied from the viewpoint of solitons. Excitation energies of compressed and stretched solitons at phases with periods 6, 5 and 7 are obtained by numerical analysis of periodic states, from which phase boundaries are determined. Each of these phases is shown to have a finite stable range, which indicates that the ground state of the model has a type of devil's staircase structure.
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  • Takashi Kimura, Hiroki Saito, Masahito Ueda
    Subject area: Quantum fuids and solids: liquid and solid helium.
    1999 Volume 68 Issue 5 Pages 1477-1480
    Published: May 01, 1999
    Released on J-STAGE: October 01, 1999
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    It is found that combining an excitation-energy sum rule with Fetter's trial wave function gives almost exact low-lying collective-mode frequencies of a trapped Bose-Einstein condensate at zero temperature.
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  • Hiori Kino, Hiroshi Kontani
    Subject area: Electron states in condensed matter.
    1999 Volume 68 Issue 5 Pages 1481-1484
    Published: May 01, 1999
    Released on J-STAGE: October 01, 1999
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    We study the electronic states of quasi-one-dimensional organic conductors using the single band Hubbard model at half-filling. We treat the effects of the on-site Coulomb interaction by the fluctuation-exchange (FLEX) method, and calculate the phase diagram and physical properties. The calculated pressure dependence of the Néel temperature coincides well with the experimental one. We also show that a pseudogap is formed in the density of states near the chemical potential and that d-wave superconductivity appears next to the antiferromagnetic state. Moreover the NMR relaxation rate increases on cooling in the low-temperature region
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  • Shin Nakamura, Yoshihiro Tadokoro, Yue Jin Shan, Tetsuro Nakamura
    Subject area: Electronic transport in condensed matter.
    1999 Volume 68 Issue 5 Pages 1485-1487
    Published: May 01, 1999
    Released on J-STAGE: October 01, 1999
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    The perovskite manganites Eu1-xSrxMnO3 are semiconductors although they exhibit ferromagnetic behavior around x=0.40. There is no evidence that charge ordering occurs. In an applied magnetic field of 15, kOe, however, the specimens with x=0.40 and 0.45 become the metallic conductors below their respective Curie temperatures of 75, K and 80, K. This magnetic field-induced insulator-to-metal transition leads a change in the resistivity exceeding 106 at 12, K. The transition is irreversible with respect to the magnetic field. The possibility of a field-induced phase transition having a lower symmetry than that at room temperature (orthorhombic) is in consideration.
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  • Atsushi Kaneko, Tomi Ohtsuki
    Subject area: Electronic transport in condensed matter.
    1999 Volume 68 Issue 5 Pages 1488-1491
    Published: May 01, 1999
    Released on J-STAGE: October 01, 1999
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    Three-dimensional quantum percolation problems are studied by analyzing energy level statistics of electrons on maximally connected percolating clusters. The quantum percolation threshold pq, which is larger than the classical percolation threshold pc, becomes smaller when magnetic fields are applied, i.e., pq(B=0)>pq(B≠ 0)>pc. The critical exponents are found to be consistent with the recently obtained values of the Anderson model, supporting the conjecture that the quantum percolation is classified onto the same universality classes of the Anderson transition. Novel critical level statistics at the percolation threshold is also reported.
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  • Mayumi Kato, Akira Endo, Makoto Sakairi, Shingo Katsumoto, Yasuhiro Iy ...
    Subject area: Electronic transport in condensed matter.
    1999 Volume 68 Issue 5 Pages 1492-1495
    Published: May 01, 1999
    Released on J-STAGE: October 01, 1999
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    We have studied the transport phenomenon in two-dimensional electron gas at a GaAs/AlGaAs heterointerface placed in a spatially alternating magnetic field. The effect of the periodic magnetic field is twofold. One is the effective mass renormalization which manifests itself as resistivity enhancement in the T → 0 limit. The other is a T2-dependent relaxation rate which is attributed to the electron-electron Umklapp scattering. A similar phenomenon observed at higher bias current provides additional support to this interpretation and forms a basis for a new method of hot electron thermometry.
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  • Akihiro Ino, Changyoung Kim, Takashi Mizokawa, Zhi–Xun Shen, Ats ...
    Subject area: Superconductivity.
    1999 Volume 68 Issue 5 Pages 1496-1499
    Published: May 01, 1999
    Released on J-STAGE: October 01, 1999
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    Using angle-resolved photoemission spectroscopy (ARPES), we observe the band structure, the Fermi surface and their doping dependences in La2-xSrxCuO4. The results reveal that the Fermi surface undergoes a dramatic change: it is holelike and centered at (π, ,π) in underdoped (x=0.1) and optimally doped (x=0.15) samples as in other cuprates, while it is electronlike and centered at (0, ,0) in heavily overdoped (x=0.3) ones. The peak in the ARPES spectra near (π/2, ,π/2) is broad and weak unlike that in other cuprates. In the underdoped and optimally doped samples, a superconducting gap (Δ = 10--15 ,meV) is observed near (π, ,0).
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  • Hiroshi Kohno, Hidetoshi Fukuyama, Manfred Sigrist
    Subject area: Magnetic properties and materials.
    1999 Volume 68 Issue 5 Pages 1500-1503
    Published: May 01, 1999
    Released on J-STAGE: October 01, 1999
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    Motivated by the observation of unusual magnetism in CexCu2Si2 (x-- 1), we study the effect of disorder, such as Ce vacancy, on the competition between superconductivity (SC) and antiferromagnetism (AF) on the basis of the phenomenological Ginzburg-Landau theory. Assuming that the AF-SC transition is of first order in a clean system, we show that a single impurity in the SC state can induce staggered magnetization by suppressing the SC around it. For finite concentration of impurities, the first-order AF-SC boundary in the clean case is replaced by a finite region where the SC and the induced AF moments coexist microscopically with spatially varying order parameters. We argue that the spin excitation spectrum in the coexistent state has a dual structure of the SC gapped mode and the low-energy spin-wave mode. In accordance with the emergence of AF out of SC ground state, the spectral weight will be transferred from the former mode to the latter one, while keeping the structure of both modes basically unchanged.
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  • Kazuaki Narita
    Subject area: Mathematical methods in physics.
    1999 Volume 68 Issue 5 Pages 1505-1507
    Published: May 01, 1999
    Released on J-STAGE: October 01, 1999
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    Eight types of highly nonlinear difference-differential equations are classified into three doublets and two exceptions. They consist of already-presented seven difference-differential equations and a new difference-differential equation. By reducing the new equation to seven bilinear equations, its multiple shock wave solution is obtained.
  • Xianguo Geng, Hon–Wah Tam
    Subject area: Mathematical methods in physics.
    1999 Volume 68 Issue 5 Pages 1508-1512
    Published: May 01, 1999
    Released on J-STAGE: October 01, 1999
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    A Darboux transformation with multi-parameters for coupled generalized nonlinear Schrödinger equations is derived with the help of a gauge transformation of the spectral problem. As a reduction, a Darboux transformation of the generalized nonlinear Schrödinger equation is obtained, from which soliton solutions of the generalized nonlinear Schrödinger equation are given.
  • Katsuhiko Yoshida, Satoru Saito
    Subject area: Mathematical methods in physics.
    1999 Volume 68 Issue 5 Pages 1513-1525
    Published: May 01, 1999
    Released on J-STAGE: October 01, 1999
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    A coupled system of two generalized logistic maps is studied. In particular influence of the coupling to the behaviour of the Julia set in two dimensional complex space is analyzed. It is proved analytically that the Julia set disappears from the complex plane uniformly as a parameter, which interpolates between chaotic phase and integrable phase, approaches to the critical value as far as the coupling strength satisfies a certain condition.
  • Tomejiro Yamagishi
    Subject area: Mathematical methods in physics.
    1999 Volume 68 Issue 5 Pages 1526-1530
    Published: May 01, 1999
    Released on J-STAGE: October 01, 1999
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    The normal mode expansion method for the Vlasov equation has been developed to multispecies plasmas in an infinite system. The perturbed charge density for the Vlasov-Poisson system in multispecies plasmas is found be the same form as the perturbed distribution function in a single species plasma. The eigenfunctions and adjoint eigenfunctions, and the orthogonality relations between them have been derived. The complete set of eigenfunctions for the charge density is constructed, which has been applied for the initial value problems. The collective discrete mode shows a singularity when the initial beam velocity coincides with the discrete eigenvalue. The continuum contribution consists of the ballistic mode and pure continuum contribution. Scalar potential and each species distribution function are also solved making use of the complete set of eigenfunctions.
  • Takeya Tsurumi, Miki Wadati
    Subject area: Classical and quantum physics: mechanics and fields.
    1999 Volume 68 Issue 5 Pages 1531-1536
    Published: May 01, 1999
    Released on J-STAGE: October 01, 1999
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    We investigate the stability of the wavefunction of theD-dimensional nonlinear Schrödinger equation with harmonic potential terms.For the repulsive case, we prove that the wavefunction is absolutely stable.For the attractive case, by extending the Zakharov's theory, we showthe emergence of the singularity of the wavefunction, termed thecollapse, in a finite time. The conditions for the collapse include an extension of Weinstein'sfor the “free” nonlinear Schrödinger field. Further, we estimate an upper bound of the collapse-timewhere the collapse occurs without oscillations.
  • Hiroshi Takasaki, Toshiya Hikihara, Tomotoshi Nishino
    Subject area: Statistical physics and thermodynamics.
    1999 Volume 68 Issue 5 Pages 1537-1540
    Published: May 01, 1999
    Released on J-STAGE: October 01, 1999
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    The density matrix renormalization group (DMRG) is a numerical method that optimizes a variational state expressed by a tensor product. We show that the ground state is not fully optimized as far as we use the standard finite system algorithm, that uses the block structure B · · B. This is because the tensors are not improved directly. We overcome this problem by using the simpler block structure B · B for the final several sweeps in the finite iteration process. It is possible to increase the numerical precision of the finite system algorithm without increasing the computational effort.
  • Sei–ichi Uramoto
    Subject area: Electronic structure of atoms and molecules: theory.
    1999 Volume 68 Issue 5 Pages 1541-1547
    Published: May 01, 1999
    Released on J-STAGE: October 01, 1999
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    The Feshbach operator formalism was used to calculate thirty doubly excited states of the H2 molecule of the symmetries 1Σ+g, u, 1Πg, u, and 1Δg, u for internuclear distances up to 8 a.u. Basis functions involving Sonine polynomials and centered on either nucleus or on the center of nuclear mass allowed accurate inclusion of many one-electron molecular orbitals. Comparison is made with previous results in the literature.
  • Tetsuya Ido, Hideyuki Kunugita
    Subject area: Atomic spectra and interactions of atoms with photons.
    1999 Volume 68 Issue 5 Pages 1548-1555
    Published: May 01, 1999
    Released on J-STAGE: October 01, 1999
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    Ionizing collisional loss rate of the metastable argon and krypton atoms inan optical lattice is compared with the rate of atoms in free space as afunction of lattice laser detuning.Contrary to a simple picture of the isolation of atoms by the latticepotential, our experimental result shows that the collision rate in opticallattice is always larger than that in free space except at a large laserdetuning of -- 103 transition linewidth.Comparing the experimental result with the theoretical values that arederived from the classical trajectory calculation of the atom, we foundthat the optical pumping to non-trapped adiabatic potential surfaceprevents the collision suppression because it keeps the number ofnon-trapped atoms to a finite value even at low excitation rate.
  • Nobuyuki Hasebe, Toshio Atarashiya, Shingo Mitani, Tadayoshi Doke, Jun ...
    Subject area: Atomic and molecular collision processes and interactions.
    1999 Volume 68 Issue 5 Pages 1556-1561
    Published: May 01, 1999
    Released on J-STAGE: October 01, 1999
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    The energy loss distributions of heavy ions (Z ≤ 8) with high energies (2 MeV/u--50 MeV/u) in thick silicon detectors with uniform thickness have been measured in a wide range of fractional energy loss, Δ E/E0, where Δ E is the energy loss and E0 is the initial energy of incident ions. The measured distributions of energetic He, Li, Be, B and C ions are in good agreement with those predicted from Livingston-Bethe's theory when Δ E/E0 < 0.2. However, the distributions for large fractional energy losses Δ E/E0 > 0.2, which are much wider than those expected from the theory, are approximately expressed by Stoquert's method considering the effect of velocity decrease into Livingston-Bethe's theory. In the previous experiment of the energy loss of heavy ions from K to Fe in thick Si detectors, Hasebe et al. obtained consistent results for heavier elements. By conbining the results in the previous and this works, it is concluded that the straggling in energy loss of heavy ions from proton to Fe with energies from about 5 MeV/u to a few hundred MeV/u in thick Si-absorber is explained by Stoquert's method.
  • Hiromi Ezaki
    Subject area: Optics.
    1999 Volume 68 Issue 5 Pages 1562-1566
    Published: May 01, 1999
    Released on J-STAGE: October 01, 1999
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    The amplitude and phase noise spectra of the internal and external field of a microcavity are calculated using the quantum mechanical Langevin equations. We assume that two-photon absorber works inside a cavity, which brings photon-number squeezing in the internal field as well as the external field. The individual frequency components of the output field have strong squeezing at cavity resonance due to the interference between the input and the cavity field, which is similar to the quadrature squeezing in a parametric oscillator and the photon number squeezing in a saturated laser oscillator. However, the degree of the squeezing is not perfect becuase the material fluctuation remains.
  • Jong–Hoon Huh, Yoshiki Hidaka, Shoichi Kai
    Subject area: Fluid dynamics.
    1999 Volume 68 Issue 5 Pages 1567-1577
    Published: May 01, 1999
    Released on J-STAGE: October 01, 1999
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    We report novel scenarios for the transitions from a stationary periodic state to spatio-temporal chaos (STC) for electroconvection in homeotropically aligned nematics, in which a constant magnetic field H is applied perpendicularly to an electric field. Above a characteristic frequency fL (in the normal roll regime), when increasing the applied electric field, stationary periodic roll patterns become unstable, and evolve to STC at a certain electric field. For f > fL we find the second stationary periodic roll pattern (i.e., abnormal rolls) at higher electric fields for H > H* , where H* is a characteristic magnetic intensity. At much higher electric field the reentrant stationary periodic rolls evolve to STC again. Reentrant stationary rolls are not observed for H < H* . Below fL (in the oblique roll regime), on the other hand, with increasing the electric field, stationary periodic rolls also become unstable toward STC. In the oblique roll regime, however, we find no reentrant stationary rolls below and above H* . The abnormal roll instability responsible for the reentrant rolls corresponds to a homogeneous azimuthal rotation of the director and plays important role for the novel scenarios. Based on systematic studies, we have determined phase diagrams in the H - ε plane, where ε is a normalized electric voltage.
  • Kazunori Koga, Hiroshi Naitou, Yoshinobu Kawai
    Subject area: The physics of plasmas and electric discharges.
    1999 Volume 68 Issue 5 Pages 1578-1584
    Published: May 01, 1999
    Released on J-STAGE: October 01, 1999
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    Local structures of the potentialand ion saturation current profile are found in an asymmetric ion sheathunder which the ion sheath instability is excited.In the high density region, the local structureof the ion saturation current profilewas observed near the sheath edge for the first time.The formation of the sheath structure is confirmedby the numerical simulation using the particle-in-cell code.In this simulation, it was observed thatthe space potential oscillates in the both two regionsdevided by the asymmetric ion sheathand, the potential swell like as the virtual anode oscillatenear the sheath edge in the driver region.It was concluded that the oscillation of the space potentialsand the ion bounce motion inside the sheathlead to excite and suppress the grid current fluctuationfrom these experimental and numerical results.
  • Maria V. A. P. Heller, Zoezer A. Brasilio, Iberê L. Caldas, Raul ...
    Subject area: The physics of plasmas and electric discharges.
    1999 Volume 68 Issue 5 Pages 1585-1591
    Published: May 01, 1999
    Released on J-STAGE: October 01, 1999
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    Wavelet spectrum and bispectrum techniques were applied to study nonstationary turbulence at the plasma edge of the TBR tokamak. Evidence of nonlinear phase coupling is more significant for magnetic than for electrostatic fluctuations. On a single discharge basis, the data also exhibit intermittent episodes of linear and nonlinear coupling between electrostatic and magnetic field oscillations. Furthermore, application of resonant perturbing magnetic fields reduces the amplitude of low frequency fluctuations and shift the frequency range of the maximum quadratic intermittent coupling to larger scales. These alterations, observed not only for magnetic but also for electrostatic oscillations, support the possibility of roughly altering electrostatic oscillations, therefore transport, through controlling oscillating magnetic fields.
  • Kazunari Hagiwara, Masayuki Kanazawa, Kazuhiro Horie, Jun Kokubun, Koh ...
    Subject area: Structure of liquids and solids; crystallography.
    1999 Volume 68 Issue 5 Pages 1592-1597
    Published: May 01, 1999
    Released on J-STAGE: October 01, 1999
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    X-ray resonant scattering, due to the anisotropic tensor of susceptibility (ATS), from magnetite, Fe3O4, near the Fe K-absorption edge, was measured from room temperature to 80, K. The energy dependence of the 002 “forbidden” reflection intensity showed two sharp peaks just above and below the edge. The azimuthal dependence of both peaks was well described by an anisotropic second rank tensor of an iron atom at the B-site (octahedral site) of the spinel lattice. The energy dependence of the reflection at 80, K was almost the same as that at room temperature except for an additional intensity enhancement due to the structural transition. The temperature hysterisis of the intensity through the transition was observed for both the allowed 004 and “forbidden” 002 reflections.
  • Meng Hau Kuok, Ser Choon Ng, Tie Liu, Zhenlin Rang, Makoto Iwata, Yosh ...
    Subject area: Equations of state, phase equilibria, and phase transitions.
    1999 Volume 68 Issue 5 Pages 1598-1601
    Published: May 01, 1999
    Released on J-STAGE: October 01, 1999
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    The temperature dependence of the elastic stiffness constant c55 in [N(CH3)4]2ZnBr4 single crystals has been measured using Brillouin scattering and the ultrasonic pulse echo overlap technique. The elastic constant c55 was found to soften strongly in both the paraelastic and ferroelastic phases. Despite the ferroelastic transition being an order-disorder type, no elastic dispersion was observed in the frequency range below -- 2, GHz. Hence the frequency of the susceptibility of the order parameter, inducing this transition, is expected to be above -- 2, GHz.
  • Jun Takeda, Junko Sakurai, Akira Nakamura, Masaya Kato, Yoshiaki Kobay ...
    Subject area: Thermal properties of condensed matter.
    1999 Volume 68 Issue 5 Pages 1602-1606
    Published: May 01, 1999
    Released on J-STAGE: October 01, 1999
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    Thermal Conductivity κ of BaCo1-xNixS2, which has quasi two-dimensional electronic nature and exhibits the Mott transition with varying x, has been measured by using polycrystalline samples. From the detailed consideration of the observed x and temperature dependence of κ, it is found that the phonon system mainly contributes to the heat conduction. The κ -x curve exhibits a significant dip structure at the insulator-metal phase boundary, where strong phonon scattering by the electron system is expected.
  • Akira Yanase, Noriaki Hamada
    Subject area: Electron states in condensed matter.
    1999 Volume 68 Issue 5 Pages 1607-1613
    Published: May 01, 1999
    Released on J-STAGE: October 01, 1999
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    Band structure of the ferrimagnetic Fe3O4 was calculated in the high temperature cubic phase by means of the full-potential linearized augmented-plane-wave method with the local spin density approximation. In the majority spin bands, the Fermi level stays in the band gap and 3d states of A site Fe are unoccupied while 3d states of B site Fe are completely occupied. In the minority spin bands, 3d states of A site are occupied and the Fermi level stays in dε bands of B site Fe. The obtained Fermi surfaces well explain the mechanism of the structural phase transition in Fe3O4. The calculated charge density has good correspondence to the recent experimental results.
  • Kazuki Kanki, Hiroshi Kontani
    Subject area: Electronic transport in condensed matter.
    1999 Volume 68 Issue 5 Pages 1614-1624
    Published: May 01, 1999
    Released on J-STAGE: October 01, 1999
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    In the normal state of high-Tc cuprates, the Hall coefficient shows remarkable temperature dependence, and its absolute value is enhanced in comparison with that value simply estimated on the basis of band structure. It has been recognized that this temperature dependence of the Hall coefficient is due to highly anisotropic quasiparticle damping rate on the Fermi surface. In this paper we further take account of the vertex correction to the current vertex arising from quasiparticle interactions. Then the transport current is transformed to a large extent from the quasiparticle velocity, and is no longer proportional to the latter. As a consequence some pieces of the Fermi surface outside of the antiferromagnetic Brillouin zone make negative contribution to the Hall conductivity, even if the curvature of the Fermi surface is hole-like.The Hall coefficient is much larger at low temperatures than the estimate made without the vertex correction. Temperature dependence of the antiferromagnetic spin correlation length is also crucial to cause remarkable temperature dependence of the Hall coefficient. In our treatment the Hall coefficient of the electron-doped cuprates can be negative despite hole-like curvature of the Fermi surface.
  • Morio Miyazawa, Hiroshi Kontani, Kosaku Yamada
    Subject area: Electronic transport in condensed matter.
    1999 Volume 68 Issue 5 Pages 1625-1631
    Published: May 01, 1999
    Released on J-STAGE: October 01, 1999
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    We present a theory of anomalous Hall effect in Sr2RuO4, which can be treated as a 2-dimensional Fermi liquid system at low temperatures. According to the recent experimental result on the Hall effect, the Hall coefficient shows strong temperature dependence at low temperatures. We try to explain the sharp increase of the Hall coefficient RH as the anomalous Hall effect, and show that the temterature dependence of RH can be plotted as ρ2, ρ being the electrical resistivity, in accordance with our theoretical prediction.However, to confirm this conclusion the data for more clean sample are highly expected.Further we show also that the orbital degeneracy plays an essential role in the anomalous Hall effect.
  • Hiroyoshi Itoh, Akinori Shibata, Takao Kumazaki, Jun–ichiro Inou ...
    Subject area: Electronic transport in condensed matter.
    1999 Volume 68 Issue 5 Pages 1632-1639
    Published: May 01, 1999
    Released on J-STAGE: October 01, 1999
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    The effects of randomness on the tunnel conductance and the tunnel magnetoresistance (TMR) are studied theoretically for ferromagnetic tunnel junctions. An emphasis is put on a combined effects of the interfacial randomness and the electronic structures of the metallic leads. The conductance is formulated by taking the randomness into account at T=0 K and zero bias limit by using the Kubo formula and the coherent potential approximation in a single orbital tight-binding model. The vertex correction to the conductance is calculated so as to satisfy the current conservation law. The tunnel conductance and the TMR with and without randomness are found to depend on the Fermi energy EF and the shape of the Fermi surface. The TMR is affected by the randomness in such a way that it can be increased by the randomness when EF is close to the band bottom, while it is decreased when EF is higher. The variation of the TMR with the barrier height and thickness is also calculated.
  • Osamu Sakai, Shunya Suzuki, Wataru Izumida, Akira Oguri
    Subject area: Electronic structure and electrical properties of surfaces, interfaces and thin films.
    1999 Volume 68 Issue 5 Pages 1640-1650
    Published: May 01, 1999
    Released on J-STAGE: October 01, 1999
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    Based on the Quantum Monte Carlo (QMC) technique, we developed a method to calculate the tunneling conductance of the quantum dot systems for which the Kondo effect becomes important.The method computes the conductance directly from the current correlation function, and is applicable to the cases in which the calculation is not reduced to the computation of single particle Green's function. We compare the calculated conductance with experiments, and found good qualitative agreement.The temperature in experiments seems to be not low enough compared withthe Kondo temperature in the mid region of the two paired Coulomb oscillation peaks.We studied the Zeeman field effect, and showed that the conductance is strongly suppressed when it has been enhanced by the Kondo effect.The conductance of an Aharonov-Bhom circuit including dots was also studied.
  • Takashi Ando, Takashi Akima, Yasumitsu Mori, Yoshiteru Maeno
    Subject area: Superconductivity.
    1999 Volume 68 Issue 5 Pages 1651-1656
    Published: May 01, 1999
    Released on J-STAGE: October 01, 1999
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    We have investigated the normal-state and superconducting properties of the 3-K superconducting phase of Sr2RuO4 with the enhanced transition temperature Tc by lamellae of ruthenium metal. In contrast to the dimensional crossover in the metallic conduction in pure Sr2RuO4 with Tc = 1.5 K, the 3-K phase retains metallic interlayer conduction at least up to 300 K. We attribute this behavior to the interlayer metallic paths through the Ru lamellae, connected by in-plane current paths. For the superconducting properties, the phase diagram of the anisotropic upper critical fields Hc2(T) indicates that Hc2//ab is strongly suppressed in the low-temperature region. The measurements of the out-of-plane resistivity ρc under magnetic fields show that the finite residual resistivity recovers above Hc2(T) of pure Sr2RuO4. This result confirms the spatial coexistence of the enhanced superconductivity with the Tc = 1.5-K region in the 3-K superconductor. In addition, we have also observed hysteresis in ρc, which appear only in the 3-K phase at low temperatures and in high fields parallel to the RuO2 plane.
  • Soh Koike, Kunihiko Yamaji, Takashi Yanagisawa
    Subject area: Superconductivity.
    1999 Volume 68 Issue 5 Pages 1657-1663
    Published: May 01, 1999
    Released on J-STAGE: October 01, 1999
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    We investigate the two-chain Hubbard model including the next nearest-neighbor transfer energies both in the interchain and intrachain directions by use of the exact-diagonalization and the variational Monte Carlo methods. We find that superconducting correlation functions are enhanced in such a situation where the density of states of the antibonding band in the neighborhood of the Fermi level enlarges due to the above-mentioned transfer energies, especially, in the situation where the Fermi level is located a little above the bottom of the antibonding band. In such a situation we find from the calculated momentum distribution function that this system is in almost one-band situation close to the two-band one. The relevance to ladder-type superconductor Sr14-xCaxCu24O41 is asserted.
  • Masafumi Sera, Shinichirou Kobayashi
    Subject area: Magnetic properties and materials.
    1999 Volume 68 Issue 5 Pages 1664-1678
    Published: May 01, 1999
    Released on J-STAGE: October 01, 1999
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    The inconsistency between the results of NMR and neutron scattering in antiferro-quadrupolar (AFQ) ordered phase II of CeB6 which remained to be solved over 15 years was explained recently by Sakai et al. by considering the Oxy type AFQ ordering where the Txyz AF octupolar interaction plays an essential role. However, various unusual magnetic properties of the AF magnetic phase III and also phase II at low magnetic fields have remained to be explained. As a first step to understand these unusual properties of CeB6, we have carried out the mean field calculation for the 4 sublattice model where the sites are divided into two Oxy quadrupolar sublattices dominated by the Txyz AF octupolar interaction and each of them is divided into two spin sublattices. Regardless of the simple 4 sublattice model, the calculated results could reproduce most of the unusual magnetic properties of CeB6. This strongly suggests that the Oxy type AFQ ordering is realized in CeB6 where both Txyz AF octupolar and AF exchange interactions play essential roles.
  • Ashis Bhattacharjee, Ralf Feyerherm, Michael Steiner
    Subject area: Magnetic properties and materials.
    1999 Volume 68 Issue 5 Pages 1679-1683
    Published: May 01, 1999
    Released on J-STAGE: October 01, 1999
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    Temperature and magnetic field dependent magnetization studies of ferrimagnetic NBu4[FeIIFeIII(ox)3] are presented, which demonstrate that the negative magnetization phenomenon in the field-cooled mode, observed only in magnetic fields lower than 5, kOe and at temperatures below 30, K. The absolute value of the ferrimagnetic saturation magnetization is 0.07μ B, estimated from the field dependence of the field-cooled magnetization at 5, K, which is only the 7%.compensation temperature as well as a temperature dependence of compensating magnetic field are observed. The hysteresis curve at 5, K under field-cooled mode under 1, kOe magnetic field shows a negative center off-set indicating the presence of large anisotropy in the material at low temperatures. The memory of the field-cooling procedure cannot be destroyed by a magnetic field of 55, kOe.
  • Norikazu Tanaka, Masakatsu Suzuki, Kazuko Motizuki
    Subject area: Magnetic properties and materials.
    1999 Volume 68 Issue 5 Pages 1684-1692
    Published: May 01, 1999
    Released on J-STAGE: October 01, 1999
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    Magnetic properties of Li2CuO2 are investigated from the both sides of localized electron picture and of itinerant electron picture. First, the anisotropy of g-factor of Cu2+ ion is studied by calculating the orbital level splitting of Cu2+ ion due to the electric crystalline field. The magnetic anisotropy energy caused by the magnetic dipole-dipole and anisotropic exchange interactions are also studied. Next, in order to make clear an effect of the hybridization between Cu-d state and the surrounding oxygen p-states, the electronic band structure is calculated for non-magnetic and antiferromagnetic states by using the full-potential linearlized augmented plane wave method. The results obtained by the band calculation are discussed in connection with the Cu-d state obtained by the localized electron model.
  • Keiichi Koyama, Tsuneaki Goto, Takeshi Kanomata, Ryunosuke Note
    Subject area: Magnetic properties and materials.
    1999 Volume 68 Issue 5 Pages 1693-1698
    Published: May 01, 1999
    Released on J-STAGE: October 01, 1999
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    Magnetization process and susceptibility measurements at high pressures up to P=12, kbar have been performed on single-crystalline FeSi in the temperature range from T=5, K to 300, K using a SQUID magnetometer with a miniature high-pressure clamp cell. From the analyses of these data, the volume dependence of the susceptibility χ for T=300, K is estimated to be d ln χ /d ln V=10.3. Using an exchange enhanced semiconductor model, the energy gap for T=0, K, Eg0, and the volume dependence of Eg0, d ln Eg0/d ln V, are evaluated to be 62, meV for P=0, kbar and -10.8, respectively.
  • H. Q. Lin, W. Y. Chen
    Subject area: Magnetic properties and materials.
    1999 Volume 68 Issue 5 Pages 1699-1702
    Published: May 01, 1999
    Released on J-STAGE: October 01, 1999
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    Using a solvable quantum mechanical model, we study the staggered magnetic ordering of the two-dimensional antiferromagnetic Heisenberg model in the ground state.
  • Takashi Kunimoto, Keigo Nagasaka, Hiroyuki Nojiri, Sebastian Luther, M ...
    Subject area: Magnetics resonances and relaxations in condensed matter; MÖssbauer effect.
    1999 Volume 68 Issue 5 Pages 1703-1710
    Published: May 01, 1999
    Released on J-STAGE: October 01, 1999
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    Magnetic excitations in the Ising ferromagnetic chain CoNb2O6 have been studied by submillimeter wave electron spin resonance in strong transverse magnetic fields. A distinct non-linear field dependence of the resonance branches and also zero field splittings have been observed. A large residual intensity of the spin-cluster resonance was found which was caused by the strong mixing among the different n-fold spin-clusters. In addition to a series of n-fold spin-cluster excitations, we also discovered a new set of spin-cluster excitation which can be attributed to non-integer n such as n-- 1.5 or n-- 2.5 for the first time. This effect is explained by the change of the quantization axis of the system in strong transverse magnetic fields. These new aspects of spin-cluster excitation show the significant effect of transverse magnetic fields on the magnetic excitation in an Ising ferromagnetic chain.
  • Chihiro Itoh, Takafumi Kondoh, Katsumi Tanimura
    Subject area: Optical properties and condensedmatter spectroscopy and other interactions of matter with particles and radiation.
    1999 Volume 68 Issue 5 Pages 1711-1715
    Published: May 01, 1999
    Released on J-STAGE: October 01, 1999
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    Optical absorption changes induced by 308-nm laser pulses and by electron pulses at low temperatures were studied for crystalline 5, 7-dodecadiyne-1, 12-diol bis[phenylcarbamate](TCDU; R-C≡C-C≡C-R, R=(CH2)4O(CO)C6H5). The dimer diradical which shows an absorption band at 3.05 eV is not formed by the electron-pulse irradiation, but is formed efficiently by irradiation with the 308-nm laser pulses. By exciting crystals with an electron pulse and a laser pulse sequentially, it is shown that the collision of excited species with the lowest triplet state is a crucial step in generating the dimer diradical. The mechanism of the formation of the dimer diradical is discussed.
  • Takeshi Iwasaki, Shigemasa Suga, Shin Imada, Akira Sekiyama, Takayuki ...
    Subject area: Optical properties and condensedmatter spectroscopy and other interactions of matter with particles and radiation.
    1999 Volume 68 Issue 5 Pages 1716-1724
    Published: May 01, 1999
    Released on J-STAGE: October 01, 1999
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    We have studied the electronic structures of ternary Ce compounds CePdX (X=As, , Sb) by means of high resolution 4d-4f resonance photoemission spectroscopy. In the Ce 4f spectra, the relative intensity ratios between the well- and poorly-screened peaks are appreciably different between these materials, while the spectra in the vicinity of the Fermi level have similar features with two shoulders split by the spin-orbit splitting. We have analyzed the experimental line-shapes of the Ce 4f spectra with using the non-crossing approximation calculation within the Anderson impurity model. It is found that the spectral difference originates from the differences of the energy positions of the valence-band and the bare Ce 4f level as well as their mutual hybridization strength.
  • Saiji Shinohara, Jun Takeda, Tomoyuki Ooike, Susumu Kurita
    Subject area: Optical properties and condensedmatter spectroscopy and other interactions of matter with particles and radiation.
    1999 Volume 68 Issue 5 Pages 1725-1730
    Published: May 01, 1999
    Released on J-STAGE: October 01, 1999
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    Both absorption and luminescence spectra of a 2-(2, 4-dinitrobenzyl)pyridine dispersed in polymer films were measured in steady state at low temperature in order to elucidate the electronic states as well as the photochromic reaction accompanied with a proton transfer. Three absorption bands due to the photoproduct were observed in a visible region after the UV photolysis. Judging from the thermal behavior of these bands, the photoproduct consists of two different kinds of species (NH and OH forms), and the OH form thermally changes to the NH form. We also found that both the NH and OH forms optically return back to the colorless form (CH2 form) on the photolysis of visible light. The luminescence spectra due to the NH and OH forms were observed for the first time. The luminescence from the OH form has vibronic structures, while that from the NH form is broad without any vibronic structures. The shorter decay time of the luminescence in comparison with the estimated radiative lifetime suggests that the non-radiative relaxation process is responsible for the decay.
  • Minoru Itoh, Yoshitoshi Bokumoto, Hisashi Yoshida
    Subject area: Optical properties and condensedmatter spectroscopy and other interactions of matter with particles and radiation.
    1999 Volume 68 Issue 5 Pages 1731-1736
    Published: May 01, 1999
    Released on J-STAGE: October 01, 1999
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    Luminescence spectra of excitons localized at iodine or bromine ions in CsCl have been studied in the temperature range 10--300 K. Two bands appear at 3.96 and 5.13 eV in CsCl:I, while three bands are observed at 3.84, 4.34 and 5.27 eV in CsCl:Br. The decay behaviors of these bands are measured under the single-bunch operation of synchrotron radiation. It is found that the 4.34-eV luminescence in CsCl:Br has a rise component around 1 ns just after the pulse excitation. In addition, time-resolved luminescence spectra are investigated through two different time windows. For the 3.96-eV luminescence in CsCl:I, the slow-component peak is located about 40 meV lower than the fast-component peak. For the 4.34-eV luminescence in CsCl:Br, the slow-component peak is located 210 meV lower than the fast one. These results suggest that an adiabatic potential energy surface has some local minima for the localized excitons in CsCl. The difference in the relaxation process of excitons between NaCl- and CsCl-type structures is discussed.
  • Dong–Seok Yang, Deok–Sin Kil, Seung–Ki Joo
    Subject area: Materials science.
    1999 Volume 68 Issue 5 Pages 1737-1739
    Published: May 01, 1999
    Released on J-STAGE: October 01, 1999
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    The local order of oxygen atoms around a titanium atom in (Ba, Sr) TiO3 (BST) thin films fabricated by the single step and the double step processes was studied by the extended X-ray absorption fine structure (EXAFS). This study shows that the double step process enhanced significantly the local order of oxygen around the titanium atom. The increase of the local order reduced the leakage current density and increased the breakdown field of the film.
  • Toshiaki Miura, Kohzo Ito, Reinosuke Hayakawa
    Subject area: Physical chemistry.
    1999 Volume 68 Issue 5 Pages 1740-1745
    Published: May 01, 1999
    Released on J-STAGE: October 01, 1999
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    The dynamical behaviors of the inclusion-dissociation transition between molecular nanotubes and flexible polymer chains have been studied by the Monte Carlo simulations. In the case of flexible polymer chains, there is large difference in time evolution curves between the inclusion processes and the dissociation processes. It is also found that the relaxation time of the inclusion or dissociation processes increases with the polymer length like a power law. This scaling exponent shows anomalous behavior near the inclusion-dissociation transition point. The simulation results indicate that the dynamical aspects of inclusion-dissociation transition in the solutions of molecular nanotubes and flexible polymer chains have many unique features, due to the disentanglement processes of polymer chains and the specific geometrical structures that forces the sequential association or dissociation of polymer segments.
  • Shûji Harada
    Subject area: Physical chemistry.
    1999 Volume 68 Issue 5 Pages 1746-1750
    Published: May 01, 1999
    Released on J-STAGE: October 01, 1999
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    Dynamical property of the desorption process of hydrogen on platinum (100 and 111) surfaces has been investigated by an electrochemical method.In the method, the desorption process of hydrogen has been measured by the recovery process of the electromotive force (EMF) after breaking the short circuit of H2 H+ electrolyte | Pt single crystal cells.These recovery process and their temperature dependence have been analyzed by a random adsorpton site distribution model. The experimental result of Pt(100)-H system was in good agreement with the present model. An unusual result of Pt(111)-H system was interpreted by surface relaxation.From the above new analysis of the desorption process, the mean stay time of hydrogen on the Pt surface was evaluated.The activation energy of the process was obtained from their Arrhenius' analyses of the mean stay time, which was correspond to the adsorption energy of hydrogen.
  • Yuishi Iwasaki, Fumiko Yonezawa
    Subject area: Biophysics.
    1999 Volume 68 Issue 5 Pages 1751-1759
    Published: May 01, 1999
    Released on J-STAGE: October 01, 1999
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    We study an error catastrophe of a self-replicating system, in which a number of bit strings with variable mutation rate compete to survive in a given rugged fitness landscape. The error catastrophe is known as a phase transition from an ordered state to a disordered state when a mutation rate increases. As a control parameter, we choose a selection pressure rather than a mutation rate. We find that our system shows the error catastrophe when the selection pressure decreases. An order parameter is introduced and the error catastrophe is studied for three types of mutant; (a) each bit has a fixed mutation rate, (b) each bit has a common variable mutation rate, and (c) each bit has a variable mutation rate. We also analyze stability of the system on the basis of the eigenvalue and the eigenvector of the transition matrix.
  • Ryota Morikawa, Yukio Saito, Hiroyuki Hyuga
    Subject area: Biophysics.
    1999 Volume 68 Issue 5 Pages 1760-1768
    Published: May 01, 1999
    Released on J-STAGE: October 01, 1999
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    Shape transformations of a vesicle during the polymerization ofan encapsulated microtubule is studied by the Monte Carlo simulations, and the morphology phase diagram is obtained in the phase space of the osmotic pressure p and the microtubule length L0.The lollipop-like shape with a spherical main body and a protrusionat one end is obtained at a negative p and a moderateL0. The φ-shape with symmetric two protrusions canbe realized only as a transient shape under a rapid polymerizationof the microtubule at low temperatures.
  • Osamu Sano
    Subject area: Other areas of research of general interest to physicists.
    1999 Volume 68 Issue 5 Pages 1769-1777
    Published: May 01, 1999
    Released on J-STAGE: October 01, 1999
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    An experimental study of the motion of a marked particle on the vertically vibrated thin granular layer forming standing waves with square cells was made under atmospheric pressure. The trajectory of the test particle whose diameter D is larger than that of the medium d is characterized by a fractional Brownian motion, reflecting the advection due to wave motion. In the range of time τ shorter than about 10 times of the period of oscillation, the relation between the variance of particle displacements and time VD(τ ) ∝ τ2h is found, where the Holder exponent 2h changes slightly from 1.88 to 1.84 as D/d decreases from 12 to 6, while it decreases drastically toward 1 as D/d decreases from 4 to 1.A simple numerical model is proposed to simulate the irregular motion of the marked particle on thin vibrating granular layer, which qualitatively explains the experimental results.
  • Sung G. Chung
    Subject area: Electronic transport in condensed matter.
    1999 Volume 68 Issue 5 Pages 1778-1779
    Published: May 01, 1999
    Released on J-STAGE: October 01, 1999
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