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Shozo Takeno
1989 Volume 58 Issue 3 Pages
759-762
Published: March 15, 1989
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Exact anharmonic-localized-mode solutions to the discrete nonlinear Schrödinger (NLS) equation defined in a
d-dimensional version of the simple cubic lattice are obtained in terms of lattice Green’s functions described by the ordinary and modified Bessel functions. A stationary or nonmoving localized mode is shown to be stable, while a moving one disperses, the rate of dispersing being smaller for a smaller moving velocity. For
d≥3 there exists a critical value of the lattice nonlinearity for the appearance of such a localized mode, and its spatial localization becomes pronounced as
d increases. For
d=1 the solution reduces in the continuum limit to the conventional one-soliton solution of the NLS equation. A very brief study is also made on the two-localized-mode problem.
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Masatoshi Shiino, Hidetoshi Nishimori, Masaya Ono
1989 Volume 58 Issue 3 Pages
763-766
Published: March 15, 1989
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Dynamical properties of the Hopfield-Hemmen-type neural networks with asymmetrical synaptic connections are studied using a nonlinear master equation which is obtained in the thermodynamic limit from the Glauber dynamics assumed for the networks. A self-consistent equation is derived for the time evolution of the overlaps of the instantaneous configuration with the built-in patterns of a finite number
p. Two fundamental types of conditions for the occurrence of limit cycle-type oscillation of the pattern overlaps are presented for the case of
p=2.
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Hidezumi Terazawa
1989 Volume 58 Issue 3 Pages
767-770
Published: March 15, 1989
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The electron energy spectrum in nuclear β-decays is affected by the weak neutral current interaction in nuclei to the order of several eV. The effect may present a serious obstacle to future measurements of the neutrino mass within the accuracy of a few eV but, once observed, it may be very useful for measurements of the weak mixing angle and the quark density in nuclei.
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Sadatoshi Taneda
1989 Volume 58 Issue 3 Pages
771-774
Published: March 15, 1989
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The structure of a fully developed turbulent pipe flow is examined using the aluminum flake method at Reynolds numbers between 3000 and 15000. The aluminum flake method enables us to determine the current state of the flow. In the near-wall region there exists an array of small-scale streamwise vortex pairs. The average transverse spacing of the vortex pairs is about 64 ν⁄
Uτ, where ν is the kinematic viscosity and
Uτ the friction velocity. In the central region, however, the existence of coherent structures is not clear.
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Hisataka Takenaka, Kousei Kamigaki, Hikaru Terauchi, Akinori Katsui
1989 Volume 58 Issue 3 Pages
775-778
Published: March 15, 1989
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Low-temperature behaviors of the incommensurate superstructure in the recently discovered new oxide superconductor, Bi
2Sr
2Ca
1Cu
2O
8+δ, are investigated by single-crystal X-ray diffraction. The amplitude of the modulation wave, peak intensities, and widths of the superstructure reflections are independent of temperature in the range from 10 K to room temperature. This implies that the superstructure is not directly associated with the superconductivity.
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Tatsuo Kobayashi, Shinji Wada, Yoshio Kitaoka, Kunisuke Asayama, Kiich ...
1989 Volume 58 Issue 3 Pages
779-782
Published: March 15, 1989
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We measured the temperature dependence of the nuclear spin-lattice relaxation time
T1 of
139La in metallic compounds (La
1−xSr
x)
2CuO
4 with
x=0.045, 0.075, 0.10 (high-
TC superconductors) and
x=0.15 (nonsuperconductor) by NQR experimentation.
T1 for
x=0.15 was found to conform to the Korringa relation (
T1T=const.) sufficiently, while the
T1 for
x=0.075 and 0.10 in the normal state showed slightly stronger temperature dependence and were shorter than that for
x=0.15, in spite of the increase of hole concentration with increasing
x. Fluctuations of Cu d-spins are considered to play an important role for
T1 in superconducting compounds. The relaxation behavior in the compound with
x=0.045 is also discussed.
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Kazuo Saitoh, Satoshi Takada
1989 Volume 58 Issue 3 Pages
783-786
Published: March 15, 1989
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The two-dimensional (2-D) Hubbard model with nearest-neighbor and next-nearest-neighbor (n.n.n.) hopping are studied using the Langevin method. Results of the staggered magnetic susceptibility and the pairing susceptibilities are shown. It is found that the effect of n.n.n. hopping destroys the antiferromagnetic correlation and assists the tendency of pairing. The possibility of superconductivity in the Hubbard model in the presence of n.n.n. hopping is discussed.
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Ken Sato, Setsuo Ichimaru
1989 Volume 58 Issue 3 Pages
787-790
Published: March 15, 1989
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Parameterized expressions for the static local-field corrections, which exactly take into account the second-order exchange-diagram contributions to the correlation energy in 2D and 3D electron liquids, are derived. Spin-dependent correlation analyses predict a possible onset of a spin-density wave instability with
k\simeq2
kF at
rs\simeq1.9 for a 2D system. As the critical conditions are approached, an attractive interaction emerges between nearest-neighbor electrons with antiparallel spins.
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Shingo Katsumoto, Fumio Komori, Naokatsu Sano, Shun-ichi Kobayashi
1989 Volume 58 Issue 3 Pages
791-794
Published: March 15, 1989
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The dielectric constant of Al
0.3Ga
0.7As:Si was measured near the metal-insulator transition (MIT). The effective electron concentration of the system was adjusted by using persistent photoconductivity. The temperature dependence of the dielectric constant is qualitatively explained by the Efros-Shikrovskii model of disordered insulators. The best fitted value of the MIT critical exponent is close to 2.
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Yoshichika \={O}nuki, Isamu Ukon, Takemi Komatsubara, Sigeru Takayanag ...
1989 Volume 58 Issue 3 Pages
795-796
Published: March 15, 1989
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We have found superconductivity in U
5Ge
3 at 0.99 K. The slope of the superconductive upper critical field at
Tc, −d
Hc2⁄d
T is 5.5 kOe/K, and
Hc2(0) is estimated to be 3.8 kOe.
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Fumio Komori, Shingo Katsumoto, Shun-ichi Kobayashi
1989 Volume 58 Issue 3 Pages
797-800
Published: March 15, 1989
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Current-voltage characteristics are studied in highly disordered Josephson networks consisting of small tin particles. For the specimens with a certain range of resistance, notable structures are observed such as negative resistance when the voltage is swept, and voltage steps when the current is swept. The structures are similar to what is expected for resistance quantization. The origin of the structure should be clarified in future.
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Hiroshi Shimahara, Susumu Misawa, Satoshi Takada
1989 Volume 58 Issue 3 Pages
801-804
Published: March 15, 1989
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The ferromagnetic susceptibility χ and the antiferromagnetic transition temperature
TAF of the strong coupling Hubbard model (
t-
J model) are studied in the improved Hubbard III approximation. It is shown that the behaviour changes drastically from the localised-spin-like to the Fermi-liquid-like with increasing the hole concentration
nh from zero, and that
TAF decreases very rapidly. The absence of the Fermi surface due to the damping of quasi-particles is discussed.
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Masahiro Matsumura, Hideki Yamagata, Yoshihiro Yamada, Kenji Ishida, Y ...
1989 Volume 58 Issue 3 Pages
805-808
Published: March 15, 1989
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Temperature dependence of nuclear resonance spectra for the chain Cu(1) and the plane Cu(2) sites was investigated in the oxygen-deficient tetragonal YBa
2Cu
3O
x (6.1≤
x≤6.4). The divergence of the spin-echo decay rate for the NQR at the Cu(1) site was observed at about 20 K, irrespective of the oxygen concentration,
x, in
x≥6.2. Below this critical temperature, only the NQR line broadening becomes significant without any resonance shifts. The spin-echo decay rate for the NMR at the Cu(2) site in the sample with
x=6.2 also increases divergently when the temperature is raised to the critical temperature. These facts directly indicate the
secondary transition associated with the moments on the Cu(2) sites at about 20 K, which is well below the Néel temperature. Some discussions are included for the magnetic structure below the transition temperature.
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Michihiro Kobayashi, Ken-ichi Mizuno, Atsuo Matsui
1989 Volume 58 Issue 3 Pages
809-812
Published: March 15, 1989
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The pressure dependence of absorption and luminescence spectra in anthracene crystals has been studied up to 4.5 GPa at 1.5 K. At ambient pressure, only free exciton luminescence is observed, while coexistence of free exciton luminescence and self-trapped exciton luminescence is observed at pressures higher than 0.16 GPa. The increase of the exciton-phonon coupling constant with pressure is discussed.
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Satoshi Tanaka, Kozo Okada, Akio Kotani
1989 Volume 58 Issue 3 Pages
813-816
Published: March 15, 1989
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We theoretically study X-ray emission spectra (XES) corresponding to the Cu 3
d→2
p electronic transition in high
Tc-superconductors by using the impurity Anderson model with five filled valence bands, and by applying a formula of a coherent second-order optical process. It is shown that XES can be explained consistently with 2
p-XPS and 2
p-XAS by the same model, and that the many-body effect due to
d-
d Coulomb interaction plays an important role in these compounds.
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A. Roy Chowdhury, Mrityunjoy De
1989 Volume 58 Issue 3 Pages
817-820
Published: March 15, 1989
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We have obtained explicit one and two soliton solutions for the discrete version of the Heisenberg Spin Chain with the help of Riemann-Hilbert approach. The asymptotic form of the two soliton solution have been analysed to obtain the phase shift of soliton scattering. Our result explicitly displays the working of a discrete version of Riemann-Hilbert methodology.
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Shinsuke Watanabe, Kazuyoshi Yoshimura
1989 Volume 58 Issue 3 Pages
821-826
Published: March 15, 1989
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The effect of dissipation on the propagation of an envelope soliton or of solitons in the bound state has been investigated through numerical integration of the nonlinear Schrödinger equation with a dissipation term. The evolution of solitons strongly depends on the strength of dissipation. In the case of one soliton, the damping rate diminishes with time as the amplitude becomes small and the nonlinear or dispersion term becomes comparable to the dissipation term. The bound state of two solitons is destroyed by an intermediate dissipation and breaks into two pulses of equal amplitude. The destruction of the bound state does not occur in the case of weak or strong dissipation.
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Michiaki Matsukawa, Shinsuke Watanabe, Hiroshi Tanaca
1989 Volume 58 Issue 3 Pages
827-830
Published: March 15, 1989
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The soliton solution of the Kadomtsev-Petviashvili and two-dimensional Boussinesq equations with quadratic and cubic nonlinearity is studied using the Hirota bilinear method. It is shown that the former has only a two-soliton solution propagating in parallel, but the latter has a two-soliton solution propagating in different directions under a certain condition. The Bäcklund transformation for the latter equation is also presented.
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Toshihiro Kawakatsu, Akira Ueda
1989 Volume 58 Issue 3 Pages
831-837
Published: March 15, 1989
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The detonation wave propagation phenomena in an exothermically reacting hard disk system are studied using the molecular dynamics method. The model reaction is (
Remark: Graphics omitted.) type exothermic isomerization reaction, where
A* corresponds to an activated complex. The detonation propagation mechanism and the relaxation processes at the wave front are compared with those of the similar reaction system with no activated complex, (
Remark: Graphics omitted.). The existence of the activated complex
A* does not change the essentials of the propagation mechanism but changes the structure of the wave front.
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H. S. Binarh, S. S. Ghumman, V. K. Mittal, H. S. Sahota
1989 Volume 58 Issue 3 Pages
838-842
Published: March 15, 1989
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The low energy weak transitions in gamma band of
160Dy have been investigated. Two new transitions namely 106.72 (4
γ+–3
γ+) and 132.98 keV (4
γ+–2
γ+) have been identified in addition to two already reported in this band. The E2 branching ratios have been calculated experimentally and are compared with IBA theory for intra as well as gamma to ground band transitions. E2/M1 mixing ratios calculated from Alaga rules as well as Greiner’s theory are in good agreement.
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R. K. Shivpuri, Archana Sharma
1989 Volume 58 Issue 3 Pages
843-847
Published: March 15, 1989
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The dependence of rapidity correlations on multiplicity, inelasticity and target mass of the interactions is investigated. The results suggest the predominant contribution of two particle clusters to multiparticle production. The cluster size has been found to be invariant with respect to multiplicity, inelasticity and target mass of the interactions.
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Hideki Kawaguchi, Shigeaki Murata
1989 Volume 58 Issue 3 Pages
848-855
Published: March 15, 1989
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Authors present a new representation of the Lienard-Wiechert potential. This representation is obtained from the study of retarded time on a heuristic point of view. It is indicated from this representation that if a motion of a charged particle is specified, the Hertzian tensor potential can be expressed by using it. From this, a multipole expansion of the field produced a moving charge is obtained in accordance with Bouwkamp and Casimir’s procdure. Moreover, as an example, synchrotron radiation will be expanded in multipole radiation.
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Zensho Yoshida, Takaaki Fujita, Yasutaka Fuke
1989 Volume 58 Issue 3 Pages
856-859
Published: March 15, 1989
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A simplified model has been given for toroidal equilibrium of a tokamak-type plasma with high-current concentrated electron beam. The plasma has a thermal pressure, and the electron beam has effective inertial pressure. Strong deformations of tokamak equilibria have been simulated by numerical calculations. Toroidal equilibria with relatively large vertical field are obtained when we consider high-energy intense electron beam. The beam orbit, which is shifted outward from the magnetic axis of the plasma, is closed by the sum of the externally applied relatively large vertical field and the poloidal magnetic field of the plasma.
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Kiyomasa Watanabe, Masahiro Wakatani
1989 Volume 58 Issue 3 Pages
860-870
Published: March 15, 1989
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Lower hybrid (LH) wave propagation and absorption caused by ion Landau damping and electron Landau damping in the heliotron/torsatron were studied for ion heating, electron heating and current drive. The analyses are based on the ray tracing method using the electromagnetic plasma dispersion relation, including warm plasma effects. In the heliotron/torsatron, the magnetic field has large ripples along the magnetic field line produced by external helical coils. This property changes the cross-sectional shape of the LH resonance layer from a circular shape in tokamaks. The refractive indices
N⊥ and
N⁄⁄, perpendicular and parallel to the magnetic field line, respectively, also change in oscillation along the ray trajectory. LH waves are absorbed at the places where the refractive index is large or at the high-field side near the helical coils.
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Shinji Tokuda, Tatsuoki Takeda, Masao Okamoto
1989 Volume 58 Issue 3 Pages
871-886
Published: March 15, 1989
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MHD equilibria of tokamak plasmas with neoclassical current effects (neoclassical conductivity and bootstrap current) were calculated self-consistently. Neoclassical effects on JFT-2M tokamak plasmas, sustained by ohmic currents, were studied. Bootstrap currents flow little for L-mode type equilibria because of low attainable values of poloidal beta, β
J. H-mode type equilibria give bootstrap currents of 30% ohmic currents for β
J attained by JFT-2M and 100% for β
J≥1.5, both of which are sufficient to change the current profiles and the resultant MHD equilibria. Neoclassical conductivity which has roughly half value of the classical Spitzer conductivity brings peaked ohmic current profiles to yield low safety factor at the magnetic axis. Neoclassical conductivity reduces the value of effective
Z(
Zeff) which is necessary to give the observed one-turn voltage but it needs impurities accumulating at the center when such peaked current profiles are not observed.
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Yoshiomi Kondoh, Nobunao Takeuchi, Satarou Yamaguchi, Yasuyuki Yagi, T ...
1989 Volume 58 Issue 3 Pages
887-893
Published: March 15, 1989
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Numerical study on the transition point of the relaxed mode for the β=0 reversed field pinch plasma is presented, where the relaxed state is expressed by μ
0j=λ
0g(
Ψ)
B with various profiles of
g(
Ψ). It is shown that the smallest positive eigenvalue in the first order approximation, which gives the transition point, increases gradually as the
g(
Ψ) profile deviates further from
g(
Ψ)≡1 for the idealized model by Taylor [J. B. Taylor: Rev. Mod. Phys.
58 (1986) 741]. It is shown that the present numerical results on the transition point become closer to the relevant experimental data compared with the idealized case obtained by Taylor. The numerical results are also shown to offer a mechanism which yields a profile consistency on the experimental
g(
Ψ) profile.
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Toshio Nasu, Kunio Nagaoka, Fumitake Itoh, Kenji Suzuki
1989 Volume 58 Issue 3 Pages
894-897
Published: March 15, 1989
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The positron life time and the angular correlation of positron annihilation radiation (ACPAR) from a plastically deformed Ni–P amorphous alloys were measured. The counting rate around θ=0 increased, the counting rate around θ=10 mrad decreased and the life time of positron increased, as a result of plastic deformation. It is interpreted that a slight growth of the free volume in the specimen by plastic deformation was detected. “Work softening” behaviour of the amorphous alloy is interpreted by this growth of the free volume.
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Ruibao Tao, Xiao Hu, Masuo Suzuki
1989 Volume 58 Issue 3 Pages
898-904
Published: March 15, 1989
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The stability of a continuous phase transition is studied. Some higher order criteria are obtained and their character formulae are also given. If a phase transition satisfies only the usual Landau’s and Lifshitz’s criteria and it violates some higher order one, then inhomogeneous fluctuation is shown here to force it to be weakly discontinuous.
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Kenkichi Okada
1989 Volume 58 Issue 3 Pages
905-913
Published: March 15, 1989
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An application of the catastrophe theory to a phenomenological description of a two-critical-point system with a special reference to rochelle salt has been developed. A suitable diffeomorphism from the butterfly potential is proposed in order to represent known dielectric and thermal properties of rochelle salt, as well as pressure effects and mixing effects with NH
4 ion to it. Some properties expected experimentally are predicted by the theory.
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Yoshihiro Ishibashi, Vladimir Dvorák
1989 Volume 58 Issue 3 Pages
914-917
Published: March 15, 1989
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The model for the reentrant phase transition, including an incommensurate phase as the sandwiched phase, is substantiated for the phase transition sequence in the perovskite-type layer compound bis-n-propylammonium tetrachloromanganate (C
3H
7NH
3)
2MnCl
4 (PAMC). By detailed considerations of the symmetry aspect of the phase transitions concerned, a thermodynamic potential functional is obtained to reproduce the phase sequence, where the pseudo-Lifshitz invariant plays an important role.
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Ryuzo Abe
1989 Volume 58 Issue 3 Pages
918-923
Published: March 15, 1989
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Critical phenomena of fluid metals are studied by observing the potential range of effective ion-ion interaction in their liquid phases. This is done by two different methods. First, the Fourier transform of March’s potential with a cutoff is calculated. Secondly, by means of quantum mechanical perturbation theory, the effective potential is derived and discussed within the lowest order approximation for the electronic dielectric function. Both methods yield the result that the effective potential is of short-range from a viewpoint of critical phenomena. On the basis of ion-ion interaction obtained by the second method, a scaling form for the critical temperature is derived and examined by the use of existent experimental data.
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Koichi Shindo, Taizo Sasaki, Nozomi Orita
1989 Volume 58 Issue 3 Pages
924-929
Published: March 15, 1989
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For two group-5B elements, arsenic and antimony, the total energies of the simple cubic (sc) and body centered cubic (bcc) structures are calculated within the local density functional formalism using
ab initio pseudopotentials. Calculated equations of state for the high pressure phase, the sc arsenic and the bcc antimony, are in excellent agreement with the experimental ones. In order to see the difference between the phase transitions for both elements, the total energies are also calculated for hypothetical pseudopotentials, which are so constructed as to have an
s (or
p) level between arsenic’s and antimony’s ones. It is shown that the difference is mainly due to the
p level.
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Yukikuni Akishige, Gendo Oomi, Taizo Yamaoto, Etsuro Sawaguchi
1989 Volume 58 Issue 3 Pages
930-939
Published: March 15, 1989
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Dielectric properties of hexagonal BaTiO
3 have been studied under a variety of conditions. Anomalies are found in the dielectric constant ε
c′ along the hexagonal
c-axis: a cusp-like anomaly at
T0=222 K and a peak at the ferroelectric Curie point of
Tc=74 K. After a dc field cooling treatment applied along the
c-axis below
T0, the ε
c′ increases appreciably at
Tc, and even in the non-ferroelectric intermediate phase (
Tc<
T<
T0) some increase of ε
c′ is found. The Curie-Weiss law ε
c′=ε
c′(∞)+
C⁄(
T−
Tp) holds above
Tc with
C=1.9×10
4 K,
Tp=70 K and ε
c′(∞)=280. The estimated spontaneous polarization at 50 K is about 2×10
−2 C/m
2. The dielectric anomaly at
Tc disappears if the sample is mechanically clamped. A complex twin configuration appears below
T0 and a rearrangement of twins occur if an intense dc biasis applied. A ferroelastic nature of the 74 K ferroelectric transition and effects of bias field on the twin configuration are discussed.
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Daizo Endoh, Terutaka Goto, Akira Tamaki, Bo Liu, Mitsuo Kasaya, Tadao ...
1989 Volume 58 Issue 3 Pages
940-948
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The elastic properties of the samarium intermetallic compounds, SmX
3 (X=Pd, In, Sn, Tl, Pb), with the AuCu
3-type structure have been investigated by means of the ultrasonic measurements. The characteristic softenings in the elastic constants reflecting the
Γ8 ground state have been found and analyzed in terms of the strain susceptibility. The rotational invariance effect of the C
44 mode in SmPd
3 is also presented.
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Katsuyasu Kawano, Jun’ichi Takahashi, Ryouhei Nakata, Minoru Sum ...
1989 Volume 58 Issue 3 Pages
949-955
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The electrical resistivities of a layered dichalcogenide TiS
2 and its Cu-intercalate were investigated in the temperature range 100 K to 350 K. The
a-axis resistivity of the Cu-intercalate showed a linear temperature dependence rather than the
T2-dependence reported in TiS
2. With increasing
x in Ti
1+xS
2 and Cu
xTiS
2, both resistivities and their slopes decrease with temperature, while the carrier concentrations enlarge up to metallike orders of 10
22 cm
−3. This origin is discussed on a common basis of the slow transition from electron-electron to electron-phonon scatterings which is due to the increase of conduction electrons of the intercalated Cu metal as well as the self-intercalated Ti metal.
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Tomi Ohtsuki, Yoshiyuki Ono
1989 Volume 58 Issue 3 Pages
956-968
Published: March 15, 1989
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The two-dimensional electronic states and the quantum Hall conductivity on the cylinder surface with finite width are analyzed numerically. A parameter θ characterizing the generalized boundary condition in the
y-direction is introduced. For each θ the sum of the
x-component of the center of mass
xνν(θ) over the states ν involved in the lowest Landau subband is shown to satisfy a sum rule and to be stable against randomness. Through different interpretations of θ, the numerical data for
xνν(θ) can be used to discuss the Hall conductivity in two different cases. One is an infinitely long strip system with finite periodicity
Ly in the
y-direction; θ is the generalized Bloch momentum in this case. The other is a real cylinder with the Aharonov-Bohm flux penetrating the cylinder along the axis, where θ represents the flux. In the latter case we can discuss the fluctuation of the Hall conductivity with respect to the flux.
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Taketoshi Kawai, Ichiro Akai, Tsutomu Karasawa
1989 Volume 58 Issue 3 Pages
969-977
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The study of exciton transfer along the stacking fault interface in BiI
3 crystals is presented by using a newly designed space-resolved spectroscopy method. The resonant luminescence lines of the excitons with exact zero Stokes shift were observed in the space-resolved spectra at a point of more than 300 μm away from the exciting laser spot. Analyzing the spatial distribution of the resonant luminescence intensities on the assumption of exciton diffusion, we obtained unusually large diffusion coefficients of more than 10
5 cm
2/sec at 4.2 K. This result indicates the existence of highly mobile excitons. The spatial distribution of the resonant luminescence intensities becomes smaller with decreasing temperature. The temperature dependence is discussed based on the weakly bound exciton model.
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Naoto Nagaosa, Yasuhiro Hatsugai, Masatoshi Imada
1989 Volume 58 Issue 3 Pages
978-997
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The spin wave theory of the two-dimensional Heisenberg antiferromagnet on a square lattice coupled with localized holes, i.e., extra spins, is investigated. This model is a limiting case of the coupled spin-fermion model presented recently to investigate the magnetic mechanism of high-
Tc superconductivity. Two schemes of the spin wave theory are proposed according to the relative magnitude of
JK (coupling between the extra and the substrate spins) to
JS (coupling between the substrate spins). The following conclusions are obtained. (1) Small antiferromagnetic (AF)
JK as well as ferromagnetic (F)
JK enhances the AF long-range order suppressing the quantum fluctuations. Large AF
JK, however, reduces the AF long-range order and enhances the quantum fluctuations. We obtain the large attractive interaction only in the latter case. (2) The susceptibility χ
⊥ perpendicular to the staggered magnetization is logarithmically divergent with respect to the external frequency ω when one extra spin is introduced.
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Nguyen Van Hieu, Ha Vinh Tan, Nguyen Toan Thang, Nguyen Ai Viet
1989 Volume 58 Issue 3 Pages
998-1002
Published: March 15, 1989
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The Green functions of the electrons in the two-band Hubbard model with the strong on-site Coulomb repulsion were calculated by means of the perturbation theory with respect to the hopping term of the Hamiltonian. It was shown that in the slave boson technique we obtain the expressions different from the results of the calculations involving directly electron operators without using slave bosons. The physical meaning of this discrepancy was discussed.
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Shoichi Nagata, Eiji Fujita, Hidemi Yamamura, Satoshi Taniguchi
1989 Volume 58 Issue 3 Pages
1003-1011
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Low temperature magnetization of amorphous ferromagnetic alloys of Fe
78B
13Si
9 has been measured in the temperature range of 4.2–310 K. The present investigation has focused on a discussion of a possible evaluation of a quantitative atomic percentage of Fe-atom in a stable α-Fe phase which nucleates and grows in a progressive annealing stage. This new attempt will be performed on the basis of magnetic properties in connection with an X-ray analysis. A mean magnetic moment of Fe atom can be deduced from the amount of the magnetization, and the analysis has been carried out with special emphasis on the spin-wave excitations. Electron diffraction and the X-ray study can identify materials precipitated by the annealing, however, it is quite difficult to give accurately quantitative amount of these materials in the crystallization process. Our new attempt leads to a fruitful discussion.
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Kazuhiko Satoh, Toshizo Fujita, Yoshiteru Maeno, Yoshichika \={O}nuki, ...
1989 Volume 58 Issue 3 Pages
1012-1020
Published: March 15, 1989
Released on J-STAGE: May 29, 2007
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Specific heat of a dense-Kondo system Ce
xLa
1−xCu
6(
x=0.0, 0.1, 0.3, 0.5, 0.9 and 1.0) has been measured systematically down to 0.1 K in various magnetic fields up to 5 T in order to clarify the transition from dilute- to dense-Kondo behavior and the nature of the heavy-fermion ground state. In zero field, the magnetic specific heat per molar Ce,
Cm, increases as the Ce concentration decreases. This tendency is attributed to the decrease of the Kondo temperature caused by the ‘chemical expansion’ effect. In a magnetic field applied along the
c-axis,
Cm⁄
T is strongly suppressed. The observed behavior of
Cm⁄
T is interpreted by using a ‘resonance model’ with the Lorentzian density of states at the Fermi level, and for the dense system, CeCu
6 the experiments suggest the development of the ‘dense’ effect below 2 T.
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Yoshitami Ajiro, Hikomitsu Kikuchi, Toshiya Inami, Toshiro Sakakibara, ...
1989 Volume 58 Issue 3 Pages
1021-1026
Published: March 15, 1989
Released on J-STAGE: June 01, 2007
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High field magnetization measurements were performed up to 40 T in the multilevel singlet ground state systems, Cs
3Cr
2X
9 (X=Cl, Br), having hierarchical higher excited magnetic states. Characteristic stair structure with three steps was observed, for the first time, in the magnetization curve of Cs
3Cr
2Cl
9 and analysed in terms of exchange-coupled Cr
3+ dimer model with the total spin
S=3. Field-induced magnetic ordering due to weak interdimer interactions is discussed and a novel type of the phase diagram composed of multiple restricted regions of magnetic ordering around the successive level-crossing fields is suggested.
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Hidetoshi Nishimori, Yukiyasu Ozeki
1989 Volume 58 Issue 3 Pages
1027-1030
Published: March 15, 1989
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We prove the existence of Néel-type long-range order in the ground state of the spin-1⁄2
XXZ model with
Δ(exchange anisotropy)>1.67 on the square lattice. We further show the existence of long-range order for
Δ>1.10 and 0≤
Δ<0.59 by assuming monotonicity of nearest neighbor correlations as functions of the system size. The assumption of monotonicity is supported by numerical calculations.
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Shigeru Takayanagi, Yoshichika \={O}nuki, Katsuyoshi Ina, Takemi Komat ...
1989 Volume 58 Issue 3 Pages
1031-1034
Published: March 15, 1989
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We report magnetic susceptibility, high-field magnetization, specific heat and electrical resistivity measurements on the orthorhombic single crystal GdCu
6. These results show GdCu
6 to be antiferromagnet which exhibits plane-type anisotropy below 16 K. The specific heat data show evidence of a low-temperature multiple phase below 16 K.
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Hideki Watanabe
1989 Volume 58 Issue 3 Pages
1035-1047
Published: March 15, 1989
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Electron spin resonance has been studied at various frequencies (6–24 GHz) on B-20 Fe
0.8Co
0.2Si single crystal, which has a long-period helical spin structure (HSS) with a cone-ferromagnetic transition at a critical field
Hc. Three resonance absorptions have been observed clearly: (a) behaving like a ferromagnetic resonance, (b) occuring around
Hc and (c) assigned to be a helical spin resonance. The resonance frequency of (c) decreases with increasing the magnetic field. Such dependence does not agree with the resonance theory for a HSS resulting from a competition between symmetric exchange interactions (SEI’s), but it agrees well with that for a HSS resulting from a competition between the SEI and the antisymmetric exchange interaction. The present results together with our previous ones give the evidence that the HSS in Fe
0.8Co
0.2Si is of the latter type.
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Yutaka Maniwa, Toshihiro Takahashi, Masashi Takigawa, Hiroshi Yasuoka, ...
1989 Volume 58 Issue 3 Pages
1048-1053
Published: March 15, 1989
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Anomalous behavior of
1H spin-lattice relaxation time
T1 in the superconducting state of β-(BEDT–TTF)
2I
3 is reported. A large enhancement of
T1−1 was observed in the high-
Tc state under pressure. The enhancement starts to appear around the transition temperature,
Tc, and forms a peak well below
Tc. The possibility of superconducting glass, which is expected in granular superconductors, is suggested. Partial disorders in the orientations of ethylene groups may be responsible for the glassy behavior.
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Tsuyoshi Murao
1989 Volume 58 Issue 3 Pages
1054-1057
Published: March 15, 1989
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The antiferromagnetic resonance in hyperfine-enhanced nuclear magnets of the singlet ground state systems is investigated by setting up the coupled equations of motion of the nuclear and the induced electronic magnetic moments. There are electron-like and nuclear-like resonances and the latter interpretes the observed feature of the antiferromagnetic resonance in Cs
2HoNaCl
6.
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Yoshihiro Ishibashi, Masatoshi Tomatsu
1989 Volume 58 Issue 3 Pages
1058-1062
Published: March 15, 1989
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A Landau-type thermodynamic theory of the successive phase transitions in the hexagonal BaTiO
3 is presented on the basis of the reported experimental data, which seem to suggest that the lowest temperature phase is of the orthorhombic point group mm2 (not 2) and ferroelectric, where the spontaneous polarization is along the
c-direction of the hexagonal phase.
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Fumihiro Aikawa, Jun Hatano, Munehiro Date, Takeo Furukawa, Hideo Futa ...
1989 Volume 58 Issue 3 Pages
1063-1069
Published: March 15, 1989
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Ferroelectric domain patterns of guanidine aluminum sulfate hexahydrate (GASH) were examined by a pyroelectric probe technique, in which the laser beam scanning and data storing were controlled by a microcomputer. It was confirmed that the averaged polarity and the magnitude of pyroelectric signal on the (0001) growth region are equal to those of either (10\bar10) or (01\bar10) growth regions, which are connected by 3-fold inversion symmetry of the crystal. The standard deviation of the pyroelectric signal intensity spectrum in the (0001) region is larger than that in the other regions. The spatial fluctuation of the pyroelectric constant in the (0001) region is larger than 25 μm, which is consistent with the inhomogeneous distribution of the polar region on the spiral patterns revealed by the powder deposition technique.
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Michiko Inoue
1989 Volume 58 Issue 3 Pages
1070-1079
Published: March 15, 1989
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The dielectric properties of the binary phase mixture have been investigated theoretically in the effective medium approximation with applications to porous glasses and Mg-PSZ. It is shown that the static dielectric constant of porous glass depends very little upon the pore geometry and size, but can be used for estimating the porosity of the material. In the far-infrared absorption of Mg-PSZ, we show that the calculated effects of the microstructure of the constituent phase are significant on the excitation spectra of the surface polaritons.
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