Volume 64, Issue 12
Displaying 1-50 of 59 articles from this issue
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Kazuya Hayata
Subject area: Mathematical methods in physics.
1995 Volume 64 Issue 12 Pages
4497-4499
Published: December 01, 1995
Released on J-STAGE: October 01, 1999
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The stability of self-focusing of d-dimensional ion channel densities in cell adhesion is studied theoretically on the basis of Smoluchowski-Kelvin equations in d+1 dimensions. An analysis based upon a method of characteristic scales shows that at least for 0
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Iwao Mogi, Masao Kamiko
Subject area: Mathematical methods in physics.
1995 Volume 64 Issue 12 Pages
4500-4503
Published: December 01, 1995
Released on J-STAGE: October 01, 1999
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The pattern formation of silver electrodeposits was investigated in magnetic fields in connection with the diffusion-limited-aggregation (DLA) perturbed by rotating convection. The electrolysis was performed in a thin-layer solution with a three-electrode system, and the in situ ac impedance was measured simultaneously in order to examine the rate-determining step. It was found that the magnetic field changes a dendritic growth pattern into the DLA-like one with the change of the rate-determining step.
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Shin–ichi Tadaki, Macoto Kikuchi
Subject area: Mathematical methods in physics.
1995 Volume 64 Issue 12 Pages
4504-4508
Published: December 01, 1995
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The jam phases in a two-dimensional cellular automaton model of traffic flow are investigated by computer simulations. Two different types of jam phases are discussed. The low-density jam configurations show fractality and self-organization. The high-density jam configurations show randomness.
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Akiyoshi Kuroda, Seiji Miyashita
Subject area: Structure of liquids and solids; crystallography.
1995 Volume 64 Issue 12 Pages
4509-4512
Published: December 01, 1995
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A phase transition is found in Ising-like Heisenberg antiferromagnets on the kagome lattice. Below the critical temperature, an exotic ferromagnetic order exists. Namely, a twofold symmetry of the system is broken and the system has a nonzero total magnetization, but no a sublattice long-range order.
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Takahito Saito, Yutaka Maniwa, Hitoshi Oda, Kiyoshi Kume, Mayumi Kosak ...
Subject area: Structure of liquids and solids; crystallography.
1995 Volume 64 Issue 12 Pages
4513-4517
Published: December 01, 1995
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Sodium-containing alkali metal fulleride, Na
2CsC
60, was studied by
13C and
23Na NMR below and above the face-centered cubic (fcc) to simple cubic (sc) phase transition temperature, T
m. It is shown that the C
60 molecules rotate faster than the rotational correlation time of 1.6× 10
-5, sec above -- 140, K and 2.4× 10
-9, sec around 300, K. Using
23Na NMR spectra broadened by the second-order quadrupole interaction, the electric field gradient at Na sites, e
2qQ/h, was estimated to be 940± 20, kHz and less than 0.1, kHz below and above T
m, respectively. The detailed analysis suggests that Na atoms in sc phase have a covalent character with C
60 molecules. It is also suggested that Na
2CsC
60 is the first metallic plastic crystal.
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Yoshio Kuramoto, Yusuke Kato
Subject area: Electron states in condensed matter.
1995 Volume 64 Issue 12 Pages
4518-4522
Published: December 01, 1995
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Thermodynamics is derived rigorously for the 1D supersymmetric t-J model and its SU(K, , 1) generalization with inverse-square exchange. The system at low temperature is described in terms of spinons, antispinons, holons and antiholons obeying fractional statistics. They are all free and render the spin susceptibility independent of electron density, and the charge susceptibility independent of magnetization. Thermal spin excitations responsible for the entropy of the SU(K, , 1) model are ascribed to free para-fermions of order K-1.
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Hiori Kino, Hidetoshi Fukuyama
Subject area: Electron states in condensed matter.
1995 Volume 64 Issue 12 Pages
4523-4526
Published: December 01, 1995
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Interrelationship among electronic structures of α -(ET)
2I
3, (ET)
2MHg(SCN)
4 and κ -(ET)
2X is studied theoretically. The effects of on-site Coulomb interaction are investigated at absolute zero within the Hartree-Fock approximation. If Coulomb interaction exceeds some critical value, various kinds of antiferromagnetic states emerge, which depend crucially on the transfer integrals between ET molecules in a unit cell. The above three types of materials are classified on the axes of two transfer integrals, leading to a unified view of the compounds.
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Ren–ichi Yamada, Shun–ichi Kobayashi
Subject area: Electron states in condensed matter.
1995 Volume 64 Issue 12 Pages
4527-4529
Published: December 01, 1995
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We studied the charge and vortex Kosterlitz-Thouless-Berezinskii transitions in random networks of small Josephson junctions. The networks were composed of small tin particles with controlled size and surface oxidation. Competition between the two transitions was clearly seen. The observed phase boundaries agree qualitatively with a theoretical phase diagram.
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Yositake Takane, Katsuhiro Nakamura
Subject area: Electron states in condensed matter.
1995 Volume 64 Issue 12 Pages
4530-4534
Published: December 01, 1995
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Based on a tunneling Hamiltonian model, the two-electron tunneling current through normal metal-superconductor junctions is studied by incorporating the influence of a dissipative electromagnetic environment with an Ohmic resistor R. We show that at low bias voltages the two-electron tunneling current displays a power-law behavior as I∝ V
4g+1, where g=e
2R/π (h/2π) at zero temperature due to electromagnetic fluctuations. This suggests that suppression of the two-electron tunneling current is more remarkable compared with the usual tunneling current in normal junctions where I∝ V
g+1.
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Masato Hedo, Yoshihiko Inada, Takashi Ishida, Etsuji Yamamoto, Yoshino ...
Subject area: Electron states in condensed matter.
1995 Volume 64 Issue 12 Pages
4535-4539
Published: December 01, 1995
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We have observed the de Haas-van Alphen (dHvA) oscillation in both the normal and superconducting mixed states of CeRu
2. The dHvA amplitude in the mixed state is extremely reduced for the large cyclotron orbit or the carrier with a large cross-sectional area of the Fermi surface compared to the small one. We have detected three dHvA branches, ranging from 6× 10
5, Oe to 2.3× 10
7, Oe. The origin of these branches is well explained by the 4f-itinerant band model.
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Motohiro Matsuura, Masaharu Kawachi, Kiyotaka Miyoshi, Makoto Hagiwara ...
Subject area: Electron states in condensed matter.
1995 Volume 64 Issue 12 Pages
4540-4543
Published: December 01, 1995
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The characteristic of intergrain phase ordering transition in a superconductive ceramic of YBa
2Cu
4O
8 is examined at zero external DC field by AC magnetic measurements. From the nonlinear response at the weak AC field limit, a negative divergence of nonlinear susceptibility χ
2 is concluded at the intergrain transition temperature T
c2 but no remarkable anomaly is found at the intragrain one T
c1. This critical phenomenon may suggest the onset of chiral glass ordering at T
c2 and necessarily a frustration in the intergrain Josephson type coupling network.
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Yasuhiro Seguchi, Takefumi Tsuboi, Toshio Kawahara, Takao Suzuki
Subject area: Electron states in condensed matter.
1995 Volume 64 Issue 12 Pages
4544-4546
Published: December 01, 1995
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A reentrant transition with respect to temperature is observed for superconducting thin films of TiN ranging in thickness from -- 4 to -- 10, nm under high magnetic fields applied parallel to the film plane. A first-order transition follows the reentrant transition at low temperatures for some of these films. These results are similar to those observed in thin Al films and indicate the existence of a high-entropy superconducting state which was predicted for a gapless superconductor under spin paramagnetic limitation.
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Masanori Ichioka, Nobuhiko Hayashi, Naoki Enomoto, Kazushige Machida
Subject area: Electron states in condensed matter.
1995 Volume 64 Issue 12 Pages
4547-4551
Published: December 01, 1995
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The vortex core structure in a d-wave superconductor is analyzed on the basis of the quasi-classical Eilenberger theory beyond the Ginzburg-Landau framework. The current and magnetic field distributions around an isolated vortex break the circular symmetry observed in s-wave pairing and show fourfold symmetry, reflecting the internal degrees of freedom in d-wave pairing, i.e., \hat k
2x-\hat k
2y in reciprocal space through the low lying quasi-particle excitations. The peculiar orientation of the flux line lattice observed recently in a cuprate is discussed in light of the present theory.
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Satoshi Fujimoto, Norio Kawakami, S.–K. Yang
Subject area: Electron states in condensed matter.
1995 Volume 64 Issue 12 Pages
4552-4556
Published: December 01, 1995
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Exact critical exponents of the Green functions for pseudo-fermions and slave bosons in the SU(N) Anderson model with U→ ∞ are obtained by using the Bethe ansatz solution and boundary conformal field theory. They are evaluated exactly for mixed valence systems and Kondo systems with crystalline fields. The results agree with the prediction of Menge and Müller-Hartmann, which coincide with those of the X-ray problem. Some implications of our results in one-dimensional chiral systems are also discussed.
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Atsuko Fukaya, Atsuko Ito, Hiroko Aruga Katori, Tsuneaki Goto
Subject area: Electron states in condensed matter.
1995 Volume 64 Issue 12 Pages
4557-4560
Published: December 01, 1995
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The diluted antiferromagnet Mn
0.80Mg
0.20TiO
3 has been studied by measuring magnetization processes and temperature variations of magnetization, and the magnetic phase diagram in the field-temperature (H-T) plane has been determined. It is demonstrated that the existence of random fields strongly affects the phase transitions. The most noteworthy result is that the H-T phase diagram consists of four phases instead of the generally known three phases: a paramagnetic, an antiferromagnetic and a spin-flop phase. We propose that the fourth phase corresponds to the region in the H-T phase diagram of Mn
0.75Zn
0.25F
2 where the behavior of the spin system is suggested to be anomalous by Cowley et al. (Z. Phys. B 75 (1989) 303).
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Ko–ichi Magishi, Yoshio Kitaoka, Guo–qing Zheng, Kunisuke ...
Subject area: Electron states in condensed matter.
1995 Volume 64 Issue 12 Pages
4561-4565
Published: December 01, 1995
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The Knight shift, the nuclear spin-lattice relaxation rate, 1/T
1, and the transverse relaxation rate, 1/T
2G, of
63Cu have been separately measured for the square and the pyramidal CuO
2 planes in HgBa
2Ca
2Cu
3O
8+δ (Hg1223) with the highest transition temperature, T
c=133, K to date. From the quantitative analysis of 1/T
1 and 1/T
2G, it is shown that the product of the staggered susceptibility and the characteristic energy of spin fluctuations around a zone boundary, χ
QΓ
Q, for the square CuO
2 plane site is larger than that for YBa
2Cu
3O
7 (YBCO
7), although that for the pyramidal CuO
2 plane site is almost the same. This enhancement of χ
QΓ
Q for the square site is considered to be responsible for the higher T
c in Hg1223 than in YBCO
7.
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Tetsuo Ohama, Hiroshi Yasuoka, Yosikazu Isikawa
Subject area: Electron states in condensed matter.
1995 Volume 64 Issue 12 Pages
4566-4569
Published: December 01, 1995
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The anisotropies of the Knight shift and the nuclear spin-lattice relaxation time (T
1) at the Sn sites have been measured up to 300, K with a magnetically aligned powder sample of CeNiSn. In contrast to the results of previous neutron scattering measurements, the anisotropy of 1/T
1 is weak and almost temperature (T)-independent. This indicates that the substantial spectral weight exists in the higher energy region than the quasielastic magnetic excitation at high T. Above about 60, K, 1/T
1 increases linearly with T, suggesting that the T dependence of the quasielastic line width is weak.
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Shuichi Murakami, Miki Wadati
Subject area: Mathematical methods in physics.
1995 Volume 64 Issue 12 Pages
4571-4582
Published: December 01, 1995
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We study the one-dimensional repulsive δ-function fermion system on an infinite interval. We construct a basis set of the Bethe ansatz eigenstates and show the completeness and the orthonormality of this basis set. We discuss the correspondence between these Bethe ansatz states and the states made by the quantum inverse scattering method. It justifies the method to study thermodynamics by the quantum Gel'fand-Levitan equations. In addition, we evaluate thermodynamic quantities by using the complete set of the Bethe ansatz states and obtain the first two terms of the virial expansions.
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Kailash Kumar
Subject area: Mathematical methods in physics.
1995 Volume 64 Issue 12 Pages
4583-4588
Published: December 01, 1995
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The basic formulation of the flight-time-integral method of Ikuta and coworkers is examined from a physical point of view. It is shown that if all equivalent flights are treated on an equal footing some corrections are needed. The content of the method then becomes the same as that of the path-integral method and therefore connection can also be made with the gradient expansion method. The expression for the drift velocity obtained in the flight-time-integral method is in agreement with that obtained from other methods and after some correction the expression for the diffusion coefficient can also be made to agree.
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Wang Ning
Subject area: Mathematical methods in physics.
1995 Volume 64 Issue 12 Pages
4589-4597
Published: December 01, 1995
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The scattering and inverse scattering problem for coupled 2× 2 matrix second order ODE is considered. An eigenfunction expansion relation is derived, and two methods for inverse scattering were discussed. As a result, the symmetric potential function or coupled coefficients matrix is shown to can be reconstructed from the reflection and transmission coefficients (continuos spectrum) and discrete spectral data.
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Masahiro Shiroishi, Miki Wadati
Subject area: Mathematical methods in physics.
1995 Volume 64 Issue 12 Pages
4598-4608
Published: December 01, 1995
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We present a new example of the tetrahedral Zamolodchikov algebra which is related to the six-vertex free-fermion model. As an application of the tetrahedral Zamolodchikov algebra, we obtain a new solution of the Yang-Baxter equation, which is a generalization of the ]R-matrix of the one-dimensional Hubbard model.
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Takeo Takagi, Mamoru Mekata
Subject area: Mathematical methods in physics.
1995 Volume 64 Issue 12 Pages
4609-4627
Published: December 01, 1995
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We have studied magnetic ordering of frustrated classical Ising spins with S=1/2 on the antiferromagnetic triangular lattice taking into account of the 2nd and the 3rd neighbor interactions by means of Monte Carlo simulations and the mean field approximation. The antiferromagnetic second and third neighbor interactions give rise to the first order phase transitions from the ground state to partially disorder states characterized by quasi-long range order with Kosterlitz-Thouless character due to the spin frustration. These partially disordered phases with 5- and 9-sublattices have commensurate sinusoidal spin density waves and related to 10- and 18-clock XY spin models, respectively.
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Masakazu Ichiyanagi
Subject area: Mathematical methods in physics.
1995 Volume 64 Issue 12 Pages
4628-4645
Published: December 01, 1995
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We investigate another possibility of developing a statistical theory in extended irreversible thermodynamics (EIT). Generalizing the principle of maximum entropy, we derive the time evolution equations of the dissipative fluxes which are second order differential equations in a scaled time. These equations involve two categories, transport coefficients and relaxation times, both of which are expressed in terms of the equal-time correlations of fluctuations of physical quantities. The reciprocal relations between the transport coefficients are proved for a nonequilibrium system undergoing a transient process. It is an aim of the present paper to perform the still missing generalization of the response theory from a different angle.
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Sumiaki Wada, Yositaka Onodera
Subject area: Mathematical methods in physics.
1995 Volume 64 Issue 12 Pages
4646-4652
Published: December 01, 1995
Released on J-STAGE: October 01, 1999
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In the mean-field approximation, the expression for free energy contains the mean field which is to be determined by the self-consistency equation. When the mean field is taken as a free parameter equivalent to the order parameter in the Landau theory, the free energy constructed from the mean-field Hamiltonian possesses the same minimum property as the Landau free energy. Utility of such an ad hoc free energy is studied analytically and numerically in comparison with the Landau free energy, with particular attention to interacting classical anharmonic oscillators.
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M. A. Mahmoud, Y. E. E. Gamal
Subject area: Electronic structure of atoms and molecules: theory.
1995 Volume 64 Issue 12 Pages
4653-4659
Published: December 01, 1995
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The time evolution of the energy distribution of the free electrons created by collisional ionization of sodium vapor resonantly excited with cw laser due to different physical mechanisms have been studied theoretically. The calculations clarified that the distribution of the electron energy tends to become non-Maxwellian for different periods of time. Also the computational model indicated that the major processes in the different stages of the plasma creation are purely collisional for both excitation and ionization. Moreover our calculations of energy spectra of electrons have characteristic peaks corresponding to associative ionization and superelastic collisions. A reasonable agreement with experiments is obtained.
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Yuki Kato, Masayuki Oikawa
Subject area: Electricity and magnetism: fields and charged particles.
1995 Volume 64 Issue 12 Pages
4660-4669
Published: December 01, 1995
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The time evolution of a nonlinear modulated wavetrain is investigated using the Dysthe equation with an additional nonlocal nonlinear damping term. It is found that the additional damping term has no significant effect on qualitative features of the modulational instability of the Stokes wave. Numerical results show that for appropriate values of the coefficient of the damping term, it is practically effective only near the crest of envelope, and causes the wave number downshift. These results suggested that two factors are essential to cause the downshift. The first is the enough nonlinearity to produce the asymmetry in spectral distribution. The second is the nonlinear dissipation that affects especially the higher components only when the wavetrain is strongly modulated.
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Jiro Mizushima, Takahiro Adachi
Subject area: Electricity and magnetism: fields and charged particles.
1995 Volume 64 Issue 12 Pages
4670-4683
Published: December 01, 1995
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Thermal convection in a two-dimensional rectangular cavity heated from below appears as a result of the pitchfork bifurcation of the motionless state when the cavity is placed horizontally. The structural stability of the pitchfork bifurcation to the tilt of the cavity is investigated by the weakly nonlinear stability theory. The four sides of the cavity are assumed to be rigid and perfectly thermal conducting. It is shown that the pitchfork bifurcation is structurally unstable to the tilt of the cavity if the bifurcated flow is anti-symmetric, and is structurally stable if it is symmetric in the horizontal direction. The results obtained from the weakly nonlinear stability theory are compared with the numerical results calculated directly from the basic equations by the Newton-Raphson method.
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Shinji Koide, Ken–Ichi Nishikawa
Subject area: Kinetic and transport theory of fluids; physical properties of gases.
1995 Volume 64 Issue 12 Pages
4684-4692
Published: December 01, 1995
Released on J-STAGE: October 01, 1999
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Turbulence caused by high plasma current in reversed field pinch (RFP) organizes the reversed toroidal magnetic field near the wall. Bessel function model (BFM) provides the clear and elegant explanation of the global feature of the relaxation of the turbulent discharge. BFM is constructed by alpha and beta effects which are familiar in the study of the Earth's magnetic field. Especially, alpha effect is important to cause and sustain the reversed magnetic field. On the other hand, numerical simulation has been advanced to investigate the relaxation process. We check the alpha effect in a three-dimensional resistive magnetohydrodynamical (MHD) simulation of RFP. We found that the helicity of the flow perpendicular to the mean magnetic field dominates the alpha effect rather than the ordinal hydrodynamical helicity for the anisotropic turbulence like RFP. This extension is supported by quasi-linear theory.
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AbouEl Magd A. Mohamed, Abdel Raouf F. Elhefnawy, Yassmen D. Mahmoud
Subject area: Kinetic and transport theory of fluids; physical properties of gases.
1995 Volume 64 Issue 12 Pages
4693-4707
Published: December 01, 1995
Released on J-STAGE: October 01, 1999
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The nonlinear electrohydrodynamic Kelvin-Helmholtz instability of two superposed dielectric fluids with interfacial transfer of mass and heat is presented for two layers of finite thickness. The fluids are subjected to a normal electric field. The method of multiple scale perturbations is used to obtain a dispersion relation for the first-order and a Ginzburg-Landau equation, for the higher-orders, describing the behaviour of the perturbed system. The stability criterion is expressible in terms of various competing parameters representing the equilibrium heat flux, latent heat of evaporation, gravity, surface tension, densities of the fluids, dielectric constants of the fluids, thickness of the layers and thermal properties of the fluids. The stability of this perturbed system is discussed both analytically and numerically near the marginal state and the stability diagrams are obtained.
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Shuji Kiyokawa
Subject area: Kinetic and transport theory of fluids; physical properties of gases.
1995 Volume 64 Issue 12 Pages
4708-4725
Published: December 01, 1995
Released on J-STAGE: October 01, 1999
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We present a density functional theory for hot dense plasmas, applicable to high Z atom, where electronic structure of atom as microscopic aspect and ionic distribution as macroscopic aspect are determined self-consistently. In this theory, the plasma is regarded as an ensemble of the virtual \lq neutral atom' or, in other words, pseudo neutral atom. We apply our theory to Fe plasmas at temperatures T=100, eV and 1, keV in the density range 0.1ρ
solid-- 200ρ
solid (ρ
solid=8.465× 10
22, cm
-3), neglecting the polarization of continuum electrons, and consequently obtain the result that the interatomic effective potential is almost the same as the bare-Coulomb type potential in one-component plasmas (OCP). From the obtained profile of the potential v
eff(r) which determines bound electron states, we suggest a possibility of resonance states. The obtained internal energy for ion subsystem is lower than the Monte Carlo result for OCP, but the difference is within a few percent.
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Chikako Moriyoshi, Kazuyuki Itoh, Tomoyuki Hikita
Subject area: Structure of liquids and solids; crystallography.
1995 Volume 64 Issue 12 Pages
4726-4732
Published: December 01, 1995
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Crystal structure of K
2Co
2(SO
4)
3 was determined at nine temperatures in the high-temperature cubic phase. In contrast to the early structural study, the split-atom calculation concludes that the SO
4 ion has a number of equilibrium arrangements. Mean-square atomic displacements become large with approaching the phase transition temperature despite no soft mode has been found. Atomic distances between Co and O are fairly shorter than the normal distance in the average structure. We explain these results by assuming that the nuclei of the low-temperature phase have already been generated in the cubic phase.
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Akira Niwata, Kazuyuki Itoh
Subject area: Structure of liquids and solids; crystallography.
1995 Volume 64 Issue 12 Pages
4733-4738
Published: December 01, 1995
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Crystal structure of CsLiSO
4 was determined at five temperatures in the high-temperature phase on the basis of the split-atom method. It turns out that the SO
4 ion executes rotational motion between two equilibrium arrangements with equal probability. It is concluded from the temperature variation of the mean-square thermal displacement that a potential barrier of the two-site SO
4 ion is higher than the thermal energy at the phase transition temperature. This disordered structure is compared with the early reported structures.
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Yasuo Yanagida, Jin Nakamura, Kichizo Asai, Nobuyoshi Yamada, Yoshitak ...
Subject area: Structure of liquids and solids; crystallography.
1995 Volume 64 Issue 12 Pages
4739-4747
Published: December 01, 1995
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Electric field gradients at
117In(←
117Cd) nuclei in BaRu
2/3(M
0.97116Cd
0.03)
1/3O
3 (M=Ca, , Cd, and Sr) were measured in the temperature range between 4 and 773, K by time-differential perturbed-angular-correlation of the 90-345, keV cascade γ -rays. For each oxide, the quadrupole interaction frequency markedly increases below a specific temperature; the temperatures are between 4 and 77, K for M=Ca, and about 300 and 600, K for M=Cd and Sr, respectively. Combined with the results of the X-ray powder diffraction measurements, it is concluded that a hexagonal-monoclinic structural phase transition, associated with a deformation of MO
6 octahedra, takes place at the temperature.
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Tomohiko Ishii, Yoshiyuki Shibayama, Toshiaki Enoki, Syunji Bandow, Ic ...
Subject area: Structure of liquids and solids; crystallography.
1995 Volume 64 Issue 12 Pages
4748-4758
Published: December 01, 1995
Released on J-STAGE: October 01, 1999
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We investigated c-axis compressibility and thermal expansion of the first and the second stage AuCl
3-GICs in order to clarify the c-axis lattice dynamical properties related to the specific structure of AuCl
3 intercalates. The results are explained in terms of not only the (00l) longitudinal acoustic phonons but also the libron mode, in which the libronic motion of planar Au
2Cl
6 molecules plays an important role, in the case of the first stage compound. The acoustic phonon analyzed based on one-dimensional Debye model gives the Debye temperature Θ
1dD=444, K with the Grüneisen constants Γ=2.49, while the contribution of the libron has the characteristic energy of Θ
E=33, K and the Grüneisen constant Γ=0.46. c-axis thermal expansion of the second stage compound is explained in terms of the acoustic and the high energy optic phonon modes which have Θ
1dD=306, K and Θ
E=320, K, respectively, since the c-axis zone folding makes the energy of the optic phonon mode lowered.
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Susumu Shimomura, Yasuhiko Fujii, Nozomu Hamaya
Subject area: Structure of liquids and solids; crystallography.
1995 Volume 64 Issue 12 Pages
4759-4765
Published: December 01, 1995
Released on J-STAGE: October 01, 1999
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The deviation of the monoclinic angle from 90°, Δβ, in the ferroelastic phase (space group P12
1/c1) of [N(CH
3)
4]
2MCl
4 (M=Fe, , Zn) has been measured as a function of hydrostatic pressure by X-ray diffraction method. The contour lines of the equal Δβ in the pressure-temperature phase diagram converge on the boundary between the normal (Pmcn) and ferroelastic phases, drawing arcs. Systematic feature among the isostructural [N(CH
3)
4]
2MX
4 (X=Cl and Br) compounds is discussed on the universality of the pressure-temperature phase diagrams.
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Yoshinori Ohmasa, Itsuro Yamamoto, Makoto Yao, Hirohisa Endo
Subject area: Structure of liquids and solids; crystallography.
1995 Volume 64 Issue 12 Pages
4766-4789
Published: December 01, 1995
Released on J-STAGE: October 01, 1999
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X-ray diffraction and electrical resistance have been measured for amorphous and crystalline Te
1-xSe
x mixtures (0≤ x≤ 1) under high pressure up to 30, GPa, and four high pressure phases of Te-Se mixtures have been observed: a monoclinic phase with 6 atoms per unit cell (M-I phase); a monoclinic phase with 4 atoms per unit cell (M-II phase); an orthorhombic phase; a β-Po-type phase. It was found for the first time that the M-II phase containing -- 60, at.\diffraction, EXAFS (extended X-ray absorption fine structure) and optical reflectivity have been measured for the pressure-quenched Te
0.4Se
0.6 specimens. Pressure-quenched Te
0.4Se
0.6 belongs to the space group Cm and has a puckered layer structure containing planer zigzag chains with period 3. Moreover, the superlattice structure with a unit cell size of 9 lattice constants along the b-axis was found. The EXAFS results suggest the existence of chemical short range order. We discuss the correlation between the structure and the electronic states in the high-pressure phases of Te-Se mixtures.
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Kazuhide Tanaka, Kenichiro Furui, Masaaki Yamada
Subject area: Electron states in condensed matter.
1995 Volume 64 Issue 12 Pages
4790-4798
Published: December 01, 1995
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The Pd
xSi
100-x system forms a homogeneous amorphous phase over a wide range of composition (0≤ x≤ 91, excluding regions near PdSi and Pd
2Si) when the alloy is deposited on a substrate by sputtering at ambient temperature. The electrical conductivity of the amorphous alloy changes characteristically with Pd concentration from a semiconductor to a metal, the transition taking place at x
c≈ 12. UPS valence band spectra show that the density of states at the Fermi level is minimal for x
c, but emerges abruptly for x≥ xc. AES SiL2, 3VV spectra show that covalent Si-Si bonding is gradually reduced and replaced by metallic Pd-Si bonding as the concentration increases beyond the transition region. Relationships between the conducting properties and electronic structure of the amorphous alloys are discussed in three characteristic ranges of Pd concentration.
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Tetsuya Mutou, Dai S. Hirashima
Subject area: Electron states in condensed matter.
1995 Volume 64 Issue 12 Pages
4799-4812
Published: December 01, 1995
Released on J-STAGE: October 01, 1999
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We study dymanical properties of the symmetric periodic Anderson model in infinite dimensions by applying the quantum Monte Carlo method and the maximum entropy method. It is found that at low temperatures a gap is developed in the density of states, in the local spin excitation spectrum and in the local charge excitation spectrum. We clarify the effects of the strong electron correlation on structure of these dynamical quantities. As the strength of interaction increases, a sharp peak evolves at a low frequency region in the spin excitation spectrum while a broad shoulder appears at a higher frequency. On the other hand, as the interaction gets strong, the charge excitation spectrum splits into a low-frequency part and a high-frequency part; the low frequency part is severely suppressed by the interaction. The reliability and the limitation of the maximum entropy method are also discussed in detail.
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Tsuyoshi Ueta
Subject area: Electron states in condensed matter.
1995 Volume 64 Issue 12 Pages
4813-4823
Published: December 01, 1995
Released on J-STAGE: October 01, 1999
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The electron focusing spectrum (EFS) is studied by solving the Schrödinger equation of electrons in an electron focusing geometry. The boundary element method (BEM) has been employed to solve the equation. The magnetic field dependence of the transmission probability from the emitter to the collector is computed and discussed, since it is considered to be proportional to EFS. It is found that the substructure of EFS is attributed to the diffraction of higher mode components in the incident wave. A modified billiard model is also proposed, in which quantization of electron waves in the emitter is included. It is confirmed that the model is useful and sufficient to study EFS.
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Naoki Shirakawa, Keizo Murata, Hisao Makino, Fumitoshi Iga, Yoshikazu ...
Subject area: Electron states in condensed matter.
1995 Volume 64 Issue 12 Pages
4824-4833
Published: December 01, 1995
Released on J-STAGE: October 01, 1999
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We have investigated the detailed temperature- and magnetic field dependence of magnetoresistance and Hall resistance in single-crystal CaVO
3-δ (δ -- 0.2). We have found that the low-temperature magnetoresistance and extraordinary contribution to the Hall resistance are both expressed well in terms of a Brillouin function B
J[gJμ
BH/k
B(T-Θ)], Θ=-2, K. From the magnetization vs magnetic field data, it may be deduced that 4$S=1. However a resistance minimum (the Kondo effect) was not observed in this system and its possible reasons are discussed.
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Go Nakamoto, Toshiro Takabatake, Hironobu Fujii, Asao Minami, Kunihiko ...
Subject area: Electron states in condensed matter.
1995 Volume 64 Issue 12 Pages
4834-4840
Published: December 01, 1995
Released on J-STAGE: October 01, 1999
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Several single crystals of CeNiSn and CeNi
0.95T
0.05Sn (T=Co and Cu) were grown and characterized by metallographic examination, electron-probe microanalysis and the measurements of resistivity, magnetoresistance, magnetic susceptibility and specific heat. Below 10, K, the semiconductor-like behavior found for dirty or substituted crystals is suppressed with decreasing impurities. For a crystal purified by the solid-state electrotransport technique, the resistivity along the orthorhombic a axis is metallic with the T
2 dependence, whereas those along the b and c axes increase below 3, K and pass through weak maxima at 0.8, K. These results suggest that the ground state of CeNiSn is not semiconducting but semimetallic with a pseudogap which closes along the a axis.
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Katsuhiko Suzuki, Tomomichi Nihei, Anju Sawada
Subject area: Electron states in condensed matter.
1995 Volume 64 Issue 12 Pages
4841-4848
Published: December 01, 1995
Released on J-STAGE: October 01, 1999
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The tunnel current of Al tunnel junctions (Al-Al
2O
3-Al) has been first measured up to ± 1200, mV at 4.2, K. It has been found that the current had the rectification property and was approximately proportional to V, V
2 and V
3. The experimental results are in good agreement with the numerical calculations introducing the bias dependence of the effective mass to the WKB approximation with trapezoidal potential. The potential values used in the calculations are consistent with the expected values from the photoemission measurement. The experimental data are also compared with the numerical calculations by the WKB approximation without the bias dependence of the effective mass and the two-band model.
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Hitoshi Sugawara, Hideyuki Sato, Tsuyoshi Yamazaki, Noriaki Kimura, Ri ...
Subject area: Electron states in condensed matter.
1995 Volume 64 Issue 12 Pages
4849-4855
Published: December 01, 1995
Released on J-STAGE: October 01, 1999
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We have grown single crystals of superconductor CeRu
2 by a zone melting method, on which we have measured the lower and upper superconducting critical fields. They are estimated as 250-400, Oe and 74, kOe at 0, K, respectively. The upper critical field H
c2 is slightly anisotropic, 64.8, kOe for the field along the ‹ 100› direction and 65.6, kOe for ‹ 110› at 1.5, K. We have also observed a characteristic feature in the superconducting mixed state.
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Katsurou Hanzawa
Subject area: Electron states in condensed matter.
1995 Volume 64 Issue 12 Pages
4856-4866
Published: December 01, 1995
Released on J-STAGE: October 01, 1999
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It is shown that isotope effects observed in the high-T
c cuprates are compatible with unconventional d-wave superconductivity due to a nonphonon mechanism. Because of the high-T
c, a considerable amount of quasi-particle damping exists at T
c, thereby giving rise to pair-breaking effect. The electron-phonon interaction is assumed to contribute only to the pair-breaking effect. The oxygen isotope effects in YBa
2Cu
3O
7 and Bi
2Sr
2CaCu
2O
8 are consistently explained by a moderate amount of the phonon contribution to the pair breaking. Using the parameters determined for these compounds, we obtain the isotope exponents comparable with the experimental results for the oxygen and copper isotope exchange in La
1.85Sr
0.15CuO
4. The increase of isotope exponent α with decreasing T
c by impurity-substitution to YBa
2Cu
3O
7 is also explained qualitatively. The oxygen isotope effect on the antiferromagnetic transition temperature in La
2CuO
4 is shown to be related with the tilting of CuO
6 octahedra and have nothing to do with the isotope effect on T
c.
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Masashige Matsumoto, Hiroyuki Shiba
Subject area: Electron states in condensed matter.
1995 Volume 64 Issue 12 Pages
4867-4881
Published: December 01, 1995
Released on J-STAGE: October 01, 1999
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In a previous paper a possibility of coexistence of two superconducting order parameters was discussed for the (1, , 1, , 0) surface of d
x2-y2-wave superconductors. In the present report physical properties are examined particularly for the time-reversal-breaking state (s± id) near the (1, , 1, , 0) surface. The nature of coexisting order parameters shows up in the local density of states. It is also shown that the superconducting current flows along the surface due to the time reversal breaking and induces the magnetic field. The induced magnetic field can be used to detect the time-reversal-breaking states experimentally.
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Shinji Sasaki, Naoyuki Narita, Isao Yamada
Subject area: Electron states in condensed matter.
1995 Volume 64 Issue 12 Pages
4882-4888
Published: December 01, 1995
Released on J-STAGE: October 01, 1999
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The exact spin-structure of KCuF
3 has been puzzling for a long time. However, recent electron paramagnetic and antiferromagneic resonance (AFMR) studies made on high-quality single crystals revealed that this compound has an eight-sublattice magnetic structure and the substantial easy direction is along [110]
p and its equivalent axes. This structure is due to the ∑
nd
nn+1· (S
n× S
n+1) interaction between nearest-neighbor spins on the c-axis; the directions of d
nn+1 are parallel to [100]
p and its equivalent axes, and are therefore orthogonal to each other in the c-plane. The analysis of the AFMR data suggested a spin flop from the [110]
p to [1\bar 10]
p at H~= 696, Oe. To confirm the spin flop, the magnetization process is investigated, and it is observed at 550, Oe. As a result, the substantial easy direction of spins suggested by the AFMR study is confirmed. In addition, the parallel and perpendicular susceptibilities, χ
// and χ
⊥ , are reexamined and are discussed on the basis of a recent improved theory for a one-dimensional Heisenberg antiferromagnet.
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Hitoshi Sugawara, Pavel Svoboda, Yuji Aoki, Hideyuki Sato, Rikio Setta ...
Subject area: Electron states in condensed matter.
1995 Volume 64 Issue 12 Pages
4889-4895
Published: December 01, 1995
Released on J-STAGE: October 01, 1999
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We have measured the electrical resistivity, specific heat, magnetic susceptibility, magnetization, magnetoresistance and de Haas-van Alphen effect to clarify the magnetic and elecrtical properties of NdCu
2. The magnetic phase diagram is presented for the field along the b-axis, which consists of five or more magnetic phases. The Fermi surface of NdCu
2 is not similar to that of YCu
2 nor to that of CeCu
2. Cyclotron masses of NdCu
2 range from 0.4 to 1.5, m
0, which are larger than 0.1-0.7, m
0 in YCu
2, but smaller than 0.5-5.3, m
0 in CeCu
2.
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Kazuo Hida
Subject area: Electron states in condensed matter.
1995 Volume 64 Issue 12 Pages
4896-4900
Published: December 01, 1995
Released on J-STAGE: October 01, 1999
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The ground state and low lying excitation of the spin 1/2 Heisenberg ladder with antiferromagnetic leg (J) and ferromagnetic rung (-λ J, , λ >0) interaction is studied by means of the density matrix renormalization group method. It is found that the state remains in the Haldane phase even for small λ -- 0.02 suggesting the continuous transition to the gapless phase at λ =0. The critical behavior for small λ is studied by the finite size scaling analysis. The result is consistent with the recent field theoretical prediction.
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Kazuko Inoue, Yoji Nakamura, Yasunori Ikeda, Yoshichika Bando, A. V. ...
Subject area: Electron states in condensed matter.
1995 Volume 64 Issue 12 Pages
4901-4905
Published: December 01, 1995
Released on J-STAGE: October 01, 1999
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The temperature dependence of lattice spacing of metastable C14-Laves phase RMn
2 (R=Y, , Gd, , Dy and Yb) has been measured up to 300, K by X-ray diffraction. Large thermal expansion was observed especially for R=Y and Dy. GdMn
2 shows a structural transition from hexagonal to orthorhombic below 80, K accompanied with a volume expansion. This indicates the appearance of a local magnetic moment of Mn 3d electrons with an antiferromagnetic order. The results are discussed together with the data on other stable C14-RMn
2 and metastable C14-TbMn
2. It is shown that the appearance of local magnetic moment of itinerant Mn 3d electrons of C14-RMn
2 at low temperatures is mainly determined by the Mn-Mn distance. C14-YMn
2, TbMn
2 and DyMn
2 are the critical substances for the onset of Mn moment.
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Shinji Yuasa, Hideki Miyajima, Yoshichika Otani, Akimasa Sakuma
Subject area: Electron states in condensed matter.
1995 Volume 64 Issue 12 Pages
4906-4913
Published: December 01, 1995
Released on J-STAGE: October 01, 1999
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Crystalline structures and magnetic properties of the FeRh
1-xPd
x system were investigated. Substitution of Pd for Rh stabilized body-centered tetragonal (bct) structure of the ordered CuAu-type with increasing axial ratio c/a from 1.18 to 1.36. The bctalloys in the range x=0.530-- 0.61 exhibited a first-order phase transition from antiferromagnetic to ferromagnetic state, while the bct alloys with x<0.530 exhibited a first-order phase transition from antiferromagnetic to Curie paramagnetic state. Both the axial ratio and the volume increased abruptly at the transitions. A new ferromagnetic phase with orthorhombic structure with the space group C
mmm was found in the bct alloys with x=0.525-- 0.61 below room temperature. This ferromagnetic phase possesses a larger magnetic moment than that of the bct phase. Reduction of the crystalline symmetry may have enhanced the magnetic moment.
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