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Masuo Suzuki
1992 年 61 巻 9 号 p.
3015-3019
発行日: 1992/09/15
公開日: 2007/06/01
ジャーナル
認証あり
A general scheme to realize nonsymmetric higher-order decomposition of exponential operators and symplectic integrators is constructed. This gives a unified theory of the previous symmetric and nonsymmetric decomposition. Ruth’s nonsymmetric third-order real decomposition is shown to be a simple example of the present general theory.
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Yoshifumi Sakamoto
1992 年 61 巻 9 号 p.
3020-3023
発行日: 1992/09/15
公開日: 2007/06/01
ジャーナル
認証あり
A method is presented to carry out molecular dynamics calculations with the optimized electron configuration at each time step and with the conservation of the total energy of the system of atoms. Although an example of calculations within the tight-binding approximation is presented, the method can also be used in
ab initio calculations. A method to obtain each eigenstate of the one-electron hamiltonian by the use of the steepest-descent equation of motion is also presented. Moreover, a feature of the flow of the electron configuration in the configuration space which is governed by the steepest-descent equation of motion is discussed.
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Masanori Aoki
1992 年 61 巻 9 号 p.
3024-3026
発行日: 1992/09/15
公開日: 2007/05/29
ジャーナル
認証あり
Vibrations of a perfect one-dimensional diatomic lattice which has quartic anharmonicity are investigated by computer simulation. We obtain a stationary localized mode which has the s-like symmetry. This self-localized mode appears above the optical band of the corresponding linear lattice.
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Hidenori Hasimoto
1992 年 61 巻 9 号 p.
3027-3029
発行日: 1992/09/15
公開日: 2007/06/01
ジャーナル
認証あり
A theorem is presented which gives the perturbation pressure \ ilde
p(
x) and velocity \ ilde
u(
x) directly when a sphere of unit radius
r=1 with its center at the origin is introduced into an unlimited viscous fluid of viscosity μ obeying the Stokes equation, of which the pressure and the velocity are
p(
x) and
u(
x).
They are
(
Remark: Graphics omitted.)
where
ur is the radial velocity
u·
x⁄
r, ω is the vorticity ∇×
u, and the prime ′ is the radial derivative d⁄d
r=(1⁄
r)(
x·∇), ∇
⁄⁄ is the tangential gradient ∇−(
x⁄
r)(d⁄d
r), and the asterisk
* on
f(
x) denotes the inversion [
f(
x)]
*=
f(
x⁄
r2).
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Shunjiro Shinohara, Ken-ichi Yamagishi, Satoshi Ohdachi, Akira Ejiri, ...
1992 年 61 巻 9 号 p.
3030-3033
発行日: 1992/09/15
公開日: 2007/05/29
ジャーナル
認証あり
The first boronization in a reversed field pinch machine has been carried out and its effects on plasma performance have been studied. From a residual gas analysis, it was found that total and partial pressures were reduced. During the first several tens of discharges, the mean plasma density normalized by a filling pressure became much higher and was nearly constant during a discharge, but these phenomena became weaker shot by shot. Radiated power, plasma resistance, CrI line intensity and high-frequency magnetic oscillations decreased. The ion temperature from Doppler broadening of the CV line changed only slightly, whereas lower temperature from the OV line was found.
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Kunihiro Sato, Hideaki Katayama, Fujio Miyawaki
1992 年 61 巻 9 号 p.
3034-3037
発行日: 1992/09/15
公開日: 2007/06/01
ジャーナル
認証あり
Electrostatic potential formed in a collisionless plasma flow near the magnetic throat is investigated by kinetic analysis under the condition that a particle source in a plasma can be neglected. It is found that the plasma flow is required to satisfy the generalized Bohm criterion at the throat for the formation of a stationary continuous potential, and then the speed of plasma flow must exceed the acoustic speed. A monotonical potential profile falling from the inside of the throat to the wall can build up only if the Bohm criterion is marginally satisfied at the throat.
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Mieko Toida, Tian Xi Zhang, Yukiharu Ohsawa
1992 年 61 巻 9 号 p.
3038-3041
発行日: 1992/09/15
公開日: 2007/06/01
ジャーナル
認証あり
Ion orbits reflected by a magnetosonic wave are theoretically analyzed, and the conditions for ion reflection are derived. In a low beta case, the reflected ions can form a ring distribution in velocity space. The velocity and energy distribution functions of those particles are obtained.
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Hiroyuki Mashiyama, Kousirou Sugimoto, Yasuaki Oohara, Hideki Yoshizaw ...
1992 年 61 巻 9 号 p.
3042-3045
発行日: 1992/09/15
公開日: 2007/06/01
ジャーナル
認証あり
The phase transition at
T3=73.5 K in Rb
2ZnCl
4 is investigated by means of neutron scattering at JRR-3M(4G). In phase 4 below
T3, superlattice reflections appear at the S-point, and their intensity increases continuously with decreasing temperature. The critical index β estimated from the superlattice intensity is 0.37. The extinction rule within the (
h,
k, 0) plane is consistent with the space group
C1
c1. Phonon dispersion of low energy is determined by inelastic scattering. Softening of the phonon branch is observed at the S-point as
T3 is approached.
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Hisatoshi Yokoyama, Yoshio Kuramoto
1992 年 61 巻 9 号 p.
3046-3049
発行日: 1992/09/15
公開日: 2007/06/01
ジャーナル
認証あり
A set of generalized Gutzwiller-type wave functions with spin and charge currents and/or spin polarization are shown to be exact eigenstates of the supersymmetric
t-
J-type model with long-range interactions. The increment of energy in the presence of currents is proportional to the square of the currents without any higher-order corrections for arbitrary size of the system. The exact excited states are identified by the absence of statistical fluctuations in the variational Monte Carlo calculation. The spin susceptibility is found to be independent of the size, as in the case of the charge susceptibility.
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Hiroaki Yamada, Masaki Goda, Yoji Aizawa, Mitsusada Sano
1992 年 61 巻 9 号 p.
3050-3053
発行日: 1992/09/15
公開日: 2007/05/29
ジャーナル
認証あり
Dynamics of an electron in a tightly binding one-dimensional disordered system is studied numerically. The time evolution of wavepackets is traced by the time-dependent Schrödinger equation. The mean square displacement of the packet scaled by the localization length shows a universal time evolution from the ballistic regime to the localized regime in an ordinary disordered system. The time evolution in the modified Bernoulli systems with long-range structural correlation also shows the same universal diffusion.
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Shigeki Ohsugi, Yoshio Kitaoka, Masafumi Kyogaku, Kenji Ishida, Kunisu ...
1992 年 61 巻 9 号 p.
3054-3057
発行日: 1992/09/15
公開日: 2007/06/01
ジャーナル
認証あり
The nuclear relaxation behavior in
s-
wave superconductors has been investigated as for Chevrel-phase superconductors, TlMo
6Se
7.5 and Sn
1.1Mo
6Se
7.5 with
Tc=12.2 K and 4.2 K, respectively. The nuclear-spin-lattice-relaxation rate, 1⁄
T1, of
119Sn in Sn
1.1Mo
6Se
7.5 reveals a distinct coherence peak just below
Tc, followed by an exponential decrease with the isotropic energy gap of 2
Δ=3.6
kBTc in a
weak coupling regime. By contrast, 1⁄
T1 of
205Tl in TlMo
6Se
7.5 possesses no coherence peak, although the exponential decrease of 1⁄
T1 has also been observed with a somewhat larger value of 2
Δ=4.5
kBTc in a
strong coupling regime. The stronger electron-phonon coupling enhances the superconducting transition temperature and at the same time, opens a decay channel to cause an intense damping of quasiparticles, resulting in the depression of the coherence peak. The comparison with high-
Tc superconductors will be discussed.
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Isao Watanabe, Kenji Kawano, Ken-ichi Kumagai, Kusuo Nishiyama, Kaneta ...
1992 年 61 巻 9 号 p.
3058-3061
発行日: 1992/09/15
公開日: 2007/06/01
ジャーナル
認証あり
Positive muon spin rotation (μ
+SR) is applied to La
2−xBa
xCuO
4 around
x=0.12, where superconductivity is suppressed remarkably. The magnetic ordering of Cu-moments appears below 35 K in the narrow range of 0.11≤
x≤0.135, where the transition from the low-temperature orthorhombic (LTO) to the low-temperature tetragonal (LTT) structure exists. The present study suggests strongly that the magnetic ordering of Cu-moments plays an important role in the suppression of the high-
Tc superconductivity around
x=0.12 in La
2−xBa
xCuO
4.
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Hikaru Kawamura
1992 年 61 巻 9 号 p.
3062-3066
発行日: 1992/09/15
公開日: 2007/05/29
ジャーナル
認証あり
The nearest-neighbor ±
JXY (plane rotator) spin glass in three dimensions is studied by means of a Monte Carlo simulation, with a focus on its chiral ordering. Finite-size scaling analysis indicates that the chiral-glass transition takes place at a finite temperature with the associated exponents ν
c=1.5±0.3 and η
c=−0.4±0.2, whereas the conventional spin-glass ordering occurs only at zero temperature. The obtained chiral-glass exponents are close to the spin-glass exponents of a three-dimensional
Ising spin glass.
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Yuichiro Ishikawa, Koji Shigematsu
1992 年 61 巻 9 号 p.
3067-3069
発行日: 1992/09/15
公開日: 2007/05/29
ジャーナル
認証あり
ESR measurements have been made on a powder sample of Sr
0.60Ca
0.40CuO
2 (the SrCuO
2 structure) at room and liquid nitrogen temperatures. Its ESR spectrum consists of seven hyperfine lines associated with a pair of identical Cu ions. The hyperfine term in the spin Hamiltonian takes the form
AS·(
I1+
I2), where
A is a hyperfine constant;
S the total electronic spin of a pair of Cu ions; and
I1,
I2 the nuclear spins of Cu ions. The spectroscopic splitting factor
g=2.18, and |
A|=72×10
−4 cm
−1. The spectrum indicates that a fine structure contributes to broadening hyperfine lines. At liquid nitrogen temperature, microwave absorption was detected over the complete range of a magnetic field sweep, being accompanied with the ESR absorption due to Cu ion pairs.
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Kazuhiro Hikami, P. P. Kulish, Miki Wadati
1992 年 61 巻 9 号 p.
3071-3076
発行日: 1992/09/15
公開日: 2007/06/01
ジャーナル
認証あり
Presented is a general method to construct quantum spin Hamiltonians with long-range pairwise interactions. The Hamiltonian is given explicitly in terms of the
R-matrices on an inhomogeneous lattice. Applications to spin-1/2 chains, higher spin chains and
Zn models are shown.
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Takeshi Iizuka, Miki Wadati
1992 年 61 巻 9 号 p.
3077-3085
発行日: 1992/09/15
公開日: 2007/06/01
ジャーナル
認証あり
A new approach to nonlinear waves in one-dimensional discontinuous media is presented. As a model a nonlinear lattice which has a discontinuity of the mass distribution is considered. Two kinds of physically interesting waves, slowly varying waves and carrier wave modulations, are investigated. For the former (latter), incident, reflected and transmitted waves are described by Korteweg-de Veries (Nonlinear Schrödinger) equations on different coordinates. The reflected and transmitted waves are constructed from the incident wave analytically. Fission and reflection of a soliton due to the discontinuity are explicitly shown in the lowest order.
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Yôhei Saika, Hidetoshi Nishimori
1992 年 61 巻 9 号 p.
3086-3095
発行日: 1992/09/15
公開日: 2007/06/01
ジャーナル
認証あり
We examine the existence of long-range order in the two-dimensional frustrated
XXZ model with next nearest neighbor interactions using the spin wave theory and the method of infrared bounds. The results show that the
XY-like system may have essentially the same properties as the isotropic Heisenberg case, while the Ising-like system is very unlikely to show non-classical behavior. We also prove the absence of twisted order.
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Junkichi Satsuma, Kenji Kajiwara, Junta Matsukidaira, Jarmo Hietarinta
1992 年 61 巻 9 号 p.
3096-3102
発行日: 1992/09/15
公開日: 2007/06/01
ジャーナル
認証あり
Solutions of the Broer-Kaup system describing one-dimensional shallow water waves are discussed by using its trilinear form. It is shown that the soliton solutions have the interesting properties that (i) their speed is determined by a dispersion relation up to an overall constant, and (ii) there is a possibility of fusion and fission of solitons. These properties reflect the particular structure of the trilinear form.
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R. E. Nettleton
1992 年 61 巻 9 号 p.
3103-3113
発行日: 1992/09/15
公開日: 2007/06/01
ジャーナル
認証あり
With the aid of projection operators \hat
P originally used by Zwanzig, phenomenological equations of irreversible thermodynamics can be derived from the Liouville equation. The phenomenological coefficients are expressed in terms of time correlations
Lc(
t) in which (1−\hat
P)
i\hat
L replaces the Liouville operator \hat
L in the formalism of Mori. Following a procedure of Lee,
Lc is calculated via an expansion of time-dependent functions in orthogonal basis functions which are made finite in number by adjustment of \hat
P. By this adjustment, one obtains a variety of analytical forms for
Lc(
t) which need not decay rapidly in order to yield phenomenological equations in Markovian form. Flexibility in \hat
P can compensate for closure and Markovian approximations.
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Tsuyoshi Horiguchi, Ojiro Nagai, Seiji Miyashita, Yukio Miyatake, Yosh ...
1992 年 61 巻 9 号 p.
3114-3124
発行日: 1992/09/15
公開日: 2007/06/01
ジャーナル
認証あり
We investigate low-temperature behaviors for an antiferromagnetic Ising model of infinite-spin on the triangular lattice. The internal energy, the specific heat, and the spontaneous sublattice-magnetizations are calculated by Monte Carlo simulations at low temperatures. The low-temperature expansions of the internal energy and the specific heat are obtained from a low-temperature expansion of the free energy and show excellent agreements with the results by the Monte Carlo simulations. The zero-temperature value of the specific heat is found to be equal to 2/3. The effects of the misfits of the first order are discussed.
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Kanpathipillai Murukesapillai
1992 年 61 巻 9 号 p.
3125-3133
発行日: 1992/09/15
公開日: 2007/06/01
ジャーナル
認証あり
Minimum thermal and cold neutron source strength necessary for the thermonuclear ignition of D–T fuel using the energy released in exothermic
3He(n, p)T reaction is determined for representative tokamak parameters, when the tokamak inner walls are lined with good thermal neutron reflectors. It is found, that D–T ignition is possible with the help of currently available neutron sources if the particle and energy confinement times exceed tens of seconds. If thermal or cold neutron sources having strength greater than 10
23 s
−1 can be constructed, then D–T ignition is possible even in plasmas having energy and particle confinement times in the range of one tenth of a second. Although the focus here is on tokamak fusion reactors the results are applicable to other type of reactors as well.
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Yoshio Tsuji
1992 年 61 巻 9 号 p.
3134-3138
発行日: 1992/09/15
公開日: 2007/05/29
ジャーナル
認証あり
Physical significance of
nτ is studied, where
n is the number density and τ the confinement time of a reaction. By introducing a fundamental parameter, the ideal and the actual ignited combuson criteria for various reactions are compared. The reason why the hurdle of
nτ is very high for nuclear fusion by magnetic confined plasma, while very low for chemical reaction and nuclear fission by thermal neutron, is clarified.
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Mamoru Tanibayashi
1992 年 61 巻 9 号 p.
3139-3145
発行日: 1992/09/15
公開日: 2007/06/01
ジャーナル
認証あり
Diffraction of light by quasi-periodic gratings constructed as Fibonacci series or three other similar series are reported. The observed diffraction patterns show rich structures which are self-similar, and the diffraction angles are related to irrational numbers.
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Rama Shankar, T. V. Singh
1992 年 61 巻 9 号 p.
3146-3152
発行日: 1992/09/15
公開日: 2007/06/01
ジャーナル
認証あり
In this paper, modified Rusanov’s third order difference scheme for quasilinear hyperbolic system of partial differential equation in non-conservative form has been presented. The method is then applied to study the unsteady motion of converging cylindrical shock waves in radiation gas dynamics. It is concluded that a cylindrical shock wave in a radiating gas increases in strength as it is propagating towards the axis. It is also observed that the effect of radiation heat transfer is to decrease the growth rate of shock strength when it is propagating towards the axis. Further, it is concluded that the effect of radiation heat transfer is to delay the shock convergence with axis and thus increase the convergence time. In the process the detailed behaviour near the axis at the time of shock coalescence is studied. The effects of various controlling parameters on the numerical results are also studied.
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Kazuaki Kurihara, Yasuhito Kiwamoto, Teruo Saito, Kiyoshi Yatsu, Syoic ...
1992 年 61 巻 9 号 p.
3153-3165
発行日: 1992/09/15
公開日: 2007/06/01
ジャーナル
認証あり
A theoretical model is developed on the electrostatic potential which is formed during fundamental electron cyclotron resonance heating in an end region of a tandem mirror. The model includes experimental conditions such as expanding magnetic flux tube, multicomponent electron temperature and secondary electrons emitted from an end plate. The axial potential profile of a collisionless plasma is analyzed with non-Maxwellian velocity distribution functions of ions and electrons. The potential profile in the plasma region, where the charge-neutrality holds, depends predominantly on the magnetic field profile. The potential drop in the sheath region in front of the end plate strongly depends on the secondary electrons and the fraction of the higher temperature component of the primary electrons.
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Hideo Sugama, Masahiro Wakatani
1992 年 61 巻 9 号 p.
3166-3177
発行日: 1992/09/15
公開日: 2007/06/01
ジャーナル
認証あり
A new anomalous transport model for resisistive interchange turbulence is derived from statistical analysis applying two-scale direct-interaction approximation to resistive magnetohydrodynamic equations with a gravity term. Our model is similar to the
K-ε model for eddy viscosity of turbulent shear flows in that anomalous transport coefficients are expressed in terms of by the turbulent kinetic energy
K and its dissipation rate ε while
K and ε are determined by transport equations. This anomalous transport model can describe some nonlocal effects such as those from boundary conditions which cannot be treated by conventional models based on the transport coefficients represented by locally determined plasma parameters.
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Naoki Yamamoto, Makoto Kikuchi, Tooru Atake, Akihiro Hamano, Yasutoshi ...
1992 年 61 巻 9 号 p.
3178-3188
発行日: 1992/09/15
公開日: 2007/06/01
ジャーナル
認証あり
BaZnGeO
4 undergoes several successive phase transitions from I to V phase. The modulated structure in the incommensurate phases (III and IV) and the commensurate-incommensurate phase transition between the IV and V phases were studied by electron microscopy. The direction of the modulation wave vector slightly deviates from the
c* direction, and the tilt angle changes with temperature. The modulated structure does not change into the discommensuration (DC) arrays around the III′ phase, but the DC’s appear in the IV phase near the C–IC phase transition temperature. The electron microscope images clearly revealed that the stripples and antistripples composed of the three DC’s were formed and moved in the DC lattice during the C–IC phase transition.
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Kêichiro Aizu
1992 年 61 巻 9 号 p.
3189-3195
発行日: 1992/09/15
公開日: 2007/06/01
ジャーナル
認証あり
It is assumed that the order parameters are two pairs {
Qα,
Qα*} and {
Qβ,
Qβ*}.
Qα is set equal to
qα exp iψ
α, and
Qβ to
qβ exp iψ
β. The ordinary or standard form of a gradient-linear term in the free energy function is
Qα*∂
xQα−
Qα∂
xQα*+
Qβ*∂
yQβ−
Qβ∂
yQβ*, which contains only ∂ψ’s and not ∂
q’s (as is well known). The present paper proposes a new form, which, in contrast to the standard form, contains only ∂
q’s and not ∂ψ’s. This new form is specified as |
Qβ|
2∂
z|
Qα|
2−|
Qα|
2∂
z|
Qβ|
2, appropriate to be called the absolute form. The
P\bar4
b2-(1/2, 0, 0) case is investigated. In this case, several commensurate phases, two incommensurate phases of the standard gradient form and two incommensurate phases of the absolute gradient form are deduced from the free energy function. Centering around the last phases, basic considerations are performed.
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Takashi Nagatani
1992 年 61 巻 9 号 p.
3196-3202
発行日: 1992/09/15
公開日: 2007/06/01
ジャーナル
認証あり
A competing two-species growth model, which is a generalized directed percolation, is presented to study the fractal structure of a self-affine pattern at the phase transition point. The growth model is described in terms of a stochastic cellular automaton. The morphology and the phase transition are investigated by using computer simulation. The phase diagram and the composition ratio in the steady state are found. The fractal structures of self-affine patterns along the phase transition line are investigated. Its fractal dimension
df=1.48±0.02 is found on the transition line. Also, near a singular point, the crossover from the Sierpinski gasket to the homogeneous mixture is found. A mean-field theory is presented.
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Masanori Inui, Shin’ichi Takeda, Tetsuo Uechi
1992 年 61 巻 9 号 p.
3203-3208
発行日: 1992/09/15
公開日: 2007/06/01
ジャーナル
認証あり
The measurement of ultrasonic velocity and sound attenuation, and density has been carried out for several liquid Bi–Ga alloys from the melting points to about 800°C. The ultrasonic velocity and its attenuation were determined by means of an ultrasonic pulse transmission method and the density was determined by a γ-ray absorption method. The adiabatic compressibility and molar volume of this system are obtained by the observed sound velocity and density. The temperature coefficient of the adiabatic compressibility is rather small in the concentration above the miscibility gap region than in the other concentration. The thermodynamic properties of this system are discussed based on the correlation between the structure and the compressibility.
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Shoji Yamamoto, Hideo Fukutome
1992 年 61 巻 9 号 p.
3209-3219
発行日: 1992/09/15
公開日: 2007/05/29
ジャーナル
認証あり
The electronic structure of the strongly correlated one dimensional Hubbard model is calculated by the resonating Hartree-Fock (Res HF) method. In the strong correlation regime with the Coulomb repulsion
U\gtrsim6, SDW solitons localize almost on the central two sites and only one kind of neutral soliton pair has a much smaller energy than the other pairs. As quantum fluctuations in a periodic chain with 12 sites, we consider up to three diradical breathers consisting of the low energy neutral soliton pair. The Res HF ground state can explain 77.8% (
U=6) and 80.1% (
U=8) of the exact correlation energy. This is much better than the Gutzwiller method to use the SDW as the reference state that explains about 50% of the correlation energy. The breather fluctuations explain the rapid decreases in the short distance of the spin and staggered spin correlation functions. Other correlation functions and the excited states due to the quantum fluctuations are studied.
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Arisato Kawabata
1992 年 61 巻 9 号 p.
3220-3229
発行日: 1992/09/15
公開日: 2007/06/01
ジャーナル
認証あり
A theory of electron scattering by potential with slow spatial variation in one-dimensional systems is proposed. It takes into account the perturbation of all order taking advantage of the long range nature of the potential. The theory is extended to the case of random potential and good agreements with the numerical calculation are obtained for wide range of parameters, while the precision of Born approximation becomes rapidly worse if the correlation length of the potential exceeds the wave length of the electron. As an application, the mobility of quantum wires limited by the surface roughness scattering is discussed.
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Morio Suzuki, Kazunori Komorita, Hiroshi Nakano, Leo Rinderer
1992 年 61 巻 9 号 p.
3230-3238
発行日: 1992/09/15
公開日: 2007/05/29
ジャーナル
認証あり
The tunneling spectroscopy was performed for the Ag or Pb–SiO–Ba Pb
0.75Bi
0.25O
3 (referred to BPBO) planer junction. For the junction with the Ag electrode, the superconducting-gap (2
Δ) is equal to 3.2 meV and 2
Δ0⁄
kBTc to 3.6. It was found that when a value of
Δ is determined so that the temperature dependence of
Δ agrees with the one of BCS theory, the temperature dependence of a recombination time of a quasiparticle largely deviates from the one of BCS theory. The deviation is explained by a fact that the
V−d
I⁄d
V characteristic contains a component of a leak-current beside a tunnel one. While, for the junction with the Pb electrode, it was found that 2
Δ at 4.2 K is equal to 9 meV. This large value comes from a zero-bias anomaly. The increase of a slope toward zero-bias in the
V−d
I⁄d
V characteristic suggests that the energy band near the Fermi energy in BPBO is strongly nonparabolic and has a gap caused by the charge density wave.
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Koji Satori, Hiroyuki Shiba, Osamu Sakai, Yukihiro Shimizu
1992 年 61 巻 9 号 p.
3239-3254
発行日: 1992/09/15
公開日: 2007/06/01
ジャーナル
認証あり
A magnetic impurity doped in a superconductor produces a localized excited state within the energy gap. This problem is studied by applying Wilson’s numerical renormalization group method. The ground state and the first excited state are traced by changing the exchange coupling constant relative to the energy gap. Thereby the position of the localized excited state within the energy gap is determined over the whole regime of the magnitude of
TK⁄
Δ (
TK: Kondo temperature,
Δ: superconducting energy gap). A crossing of the lowest doublet and singlet is clearly observed at
TK⁄
Δ\simeq0.3. The ferromagnetic and Ising cases have been studied also. In the ferromagnetic case the localized excited state stays close to the gap edge since the exchange coupling is renormalized to a weak coupling. The case of the Ising-like
sd coupling, which is exactly solvable, can be used to check the reliability of the present approach and the effect of the discretization.
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Tetsuya Takeuchi, Mitsuru Ono, Hidenobu Hori, Taturu Yosida, Akio Yama ...
1992 年 61 巻 9 号 p.
3255-3261
発行日: 1992/09/15
公開日: 2007/05/29
ジャーナル
認証あり
Magnetization measurements have been performed on the single crystal samples of Ni(C
2H
8N
2)
2NO
2(ClO
4), NENP, and Ni(C
3H
10N
2)
2NO
2(ClO
4), NINO in pulsed high magnetic fields. No magnetization appears up to about 10 T reflecting the presence of the Haldane gap and the linear magnetization appears in both compounds above this field. The observed anisotropy of the transition field is explained by the Haldane gap energy
Eg and the crystalline field constants
D and
E in the lowest excited triplet. The parameters are estimated as
Eg=16.8 K,
D=−16.1 K, and
E=−1.3 K and
Eg=14.2 K,
D=−11.5 K and
E=2.1 K for NENP and NINO, respectively.
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Tetsuya Takeuchi, Hidenobu Hori, Taturu Yosida, Akio Yamagishi, Koichi ...
1992 年 61 巻 9 号 p.
3262-3266
発行日: 1992/09/15
公開日: 2007/05/29
ジャーナル
認証あり
Magnetization measurements have been performed on the Haldane gap materials (CH
3)
4NNi(NO
2)
3 (TMNIN) and Ni(C
3H
10N
2)
2N
3(ClO
4) (NINAZ) in pulsed high magnetic fields. TMNIN shows a typical magnetization profile of the Haldane material with the gap energy of 4.1 K. Quenching of the gap appears around 2.7 Tesla(T) and magnetic saturation is obtained above 30 T. In NINAZ, however, the quenching appears at around 30 T reflecting a large Haldane gap energy with the magnitude of 44.3 K.
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Kazuhiko Satoh, Akira Fukada, Izuru Umehara, Yoshichika \={O}nuki, Hid ...
1992 年 61 巻 9 号 p.
3267-3276
発行日: 1992/09/15
公開日: 2007/05/29
ジャーナル
認証あり
We have measured the electrical resistivity, Hall coefficient, thermoelectric power, magnetoresistance, magnetic susceptibility and magnetization of the antiferromagnetic Kondo-lattice compound CeCu
2 using a high-quality single crystal. Anisotropy reflected in the above quantities is explained by the orthorhombic crystalline electric field. We discuss the metamagnetic behavior and the negative magnetoresistance which scales with a square of the magnetization.
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Tsutomu Momoi, Masuo Suzuki
1992 年 61 巻 9 号 p.
3277-3286
発行日: 1992/09/15
公開日: 2007/06/01
ジャーナル
認証あり
The chiral order in the spin 1/2
XXZ antiferromagnet
H=
J∑(σ
ixσ
jx+σ
iyσ
jy+
Δσ
izσ
jz) and especially in the
XY antiferromagnet on a two-dimensional triangular lattice is studied using the super-effective-field theory. In the
XY model the size dependence of the critical temperatures indicates the existence of the long-range chiral-order at sufficiently low temperatures in the infinite system. Phase diagram of the chiral order in the
XXZ antiferromagnet is studied.
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Tatsuichi Hamasaki, Hidenori Kubo
1992 年 61 巻 9 号 p.
3287-3291
発行日: 1992/09/15
公開日: 2007/05/29
ジャーナル
認証あり
In order to clarify the spin structure of mixed antiferromagnets Co
1−xNi
xCl
2·6H
2O, proton NMR spectra are observed in an applied magnetic field along the
b axis perpendicular to each easy axis. The resonance fields shift gradually from their positions in CoCl
2·6H
2O to those in NiCl
2·6H
2O upon increasing Ni concentration,
x. From analyzing the Ni concentration dependence of these resonance fields, it is shown that the spin directions of these mixtures vary smoothly from the
c axis (the easy axis of CoCl
2·6H
2O) to the
a″ axis (the easy axis of NiCl
2·6H
2O) that is in a good agreement with the model proposed by Matsubara
et al. It is confirmed that the oblique antiferromagnetic phase does not occur.
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Hidekazu Tanaka, Tetsuya Kato, Katsunori Iio, Kazukiyo Nagata
1992 年 61 巻 9 号 p.
3292-3302
発行日: 1992/09/15
公開日: 2007/06/01
ジャーナル
認証あり
The magnetic properties of RbVBr
3 with a deformed CsNiCl
3 structure were investigated by means of the susceptibility and torque measurements. RbVBr
3 undergoes the successive transitions,
TN1=28.0 K and
TN2=21.3 K and 19.0 K on heating and cooling, respectively. A large hysteresis was observed for the transition at
TN2. Metastable states appear between the intermediate phase and low-temperature phase. The intermediate phase has the weak ferromagnetic moment of the order of 10
−5 μ
B perpendicular to the
c-axis, while the low-temperature phase does not. It is compatible with the crystal structure that the weak moment due to the Dzyaloshinsky-Moriya interaction appears in linear chains. It is concluded that in the intermediate phase the spins form a collinear structure, probably ferrimagnetic one in the
c-plane and a triangular one in the low-temperature phase.
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Taichi Terashima, Norimichi Kojima
1992 年 61 巻 9 号 p.
3303-3312
発行日: 1992/09/15
公開日: 2007/05/29
ジャーナル
認証あり
The magnetic susceptibilities and magnetizations of incommensurate layer compounds (CeS)
1.2NbS
2 and (CeS)
0.6NbS
2 are reported. The magnetic susceptibilities in the paramagnetic region of the above two compounds are analyzed taking account of the crystal field acting on Ce
3+ and the molecular field. The crystal field splitting of
2F5⁄2 multiplet (Ce
3+) is estimated at ca. 500 K. The large splitting suggests that the screening of the crystal field by conduction electrons is weak in the CeS layer. The compound (CeS)
1.2NbS
2 orders antiferromagnetically near 3 K accompanied by a weak-ferromagnetic moment, while a magnetic ordering with a spontaneous magnetization is observed near 3 K in (CeS)
0.6NbS
2. Both the two compounds display a metamagnetic transition at 2.3 kOe (
T=2.0 K). Possible magnetic structures are discussed in terms of ferromagnetic CeS layers.
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Masahito Yoshizawa, Hirotaka Seki, Kôki Ikeda, Kaoru Okuno, Mits ...
1992 年 61 巻 9 号 p.
3313-3321
発行日: 1992/09/15
公開日: 2007/06/01
ジャーナル
認証あり
Magnetization and electrical resistivity of chemically analyzed Ni
3Al alloys have been measured. The sample Ni
75.07Al
24.93 shows a ferromagnetic transition at 43.7 K. This result confirms the ferromagnetism of stoichiometric Ni
3Al. The magnetic field effect on the electrical resistivity has been investigated from a viewpoint of quenching of spin fluctuation. The suppression of the coefficient
A of the squared temperature in the resistivity has been observed for both weakly ferromagnetic and strongly paramagnetic samples. Characteristic magnetic field
H0 for the quenching of spin fluctuation was estimated from the resistivity data. The value of
H0 shows a minimum near the boundary between paramagnetic and ferromagnetic compositions.
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Yoshikazu Suzumura, Hidetoshi Fukuyama
1992 年 61 巻 9 号 p.
3322-3330
発行日: 1992/09/15
公開日: 2007/06/01
ジャーナル
認証あり
The insulating state of (R
1, R
2-DCNQI)
2Cu salts showing both the mixed valence of Cu
+ and Cu
++ and the three-fold lattice distortion has been examined by the mean-field theory to the periodic Anderson model where two one-dimensional conduction bands with the electron-phonon interaction are coupled to Cu ions. For the choice of the interaction constant which leads to approximately Cu
+4⁄3 as an average, it is shown that modulations of both charge density and spin density coexist in the ground state and that the phase transition at finite temperature is of the first order.
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Nobuo Furukawa, Masatoshi Imada
1992 年 61 巻 9 号 p.
3331-3354
発行日: 1992/09/15
公開日: 2007/06/01
ジャーナル
認証あり
The Hubbard model on a square lattice in the ground state is investigated. Various aspects of Mott transition at half-filling are clarified from the quantum Monte Carlo study. Critical exponents of the transition for charge and spin correlations are estimated. For the doping concentration δ, the charge susceptibility is proportional to δ
−1 indicating the divergence of charge mass for δ→0, while the spin susceptibility is always finite and not singular near δ=0. Several theoretical consequences of the above results are discussed. Incommensurate peak amplitude of spin correlation scales as (δ−δ
c)
−1 with δ
c<0.01 in disagreement with RPA results ln(δ−δ
c). The antiferromagnetic order at the half-filling also shows strong correlation character and is not sensitive to the shape of the fermi surface, while the incommensurate peak observed away from the half-filling is sensitively suppressed by the loss of partial nesting consistently with the weak coupling picture. Comparisons with experimental indications of high-
Tc oxides are made.
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Kenji Nakajima, Kazuhisa Kakurai, Haruhiro Hiraka, Hidekazu Tanaka, Ka ...
1992 年 61 巻 9 号 p.
3355-3360
発行日: 1992/09/15
公開日: 2007/05/29
ジャーナル
認証あり
Quasielastic and inelastic neutron scattering experiments on
S=1 quasi 1-D Heisenberg antiferromagnet, RbNiCl
3 were performed. The temperature dependence of the spin correlation length suggests a finite 1-D correlation even at
T=0 (K). The dispersion relation in the 3-D ordered phase can be well described by the phenomenological theory of a quasi 1-D Heisenberg antiferromagnet including the Haldane effect. Our results support early works on CsNiCl
3 suggesting the influence of the novel quantum effect even in 3-D ordered phase of the quasi 1-D,
S=1 Heisenberg antiferromagnet.
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Masayuki Kawakami, Jiro Watarizaki
1992 年 61 巻 9 号 p.
3361-3369
発行日: 1992/09/15
公開日: 2007/06/01
ジャーナル
認証あり
NMR measurements have been made for Y
2Co
14B and Gd
2Co
14B by the steady-state and spin-echo methods in zero external field as a function of temperature. By the steady-state method, the
59Co domain signals with quadrupole splittings which originate from six non-equivalent Co sites have been observed together with wall signals for the two compounds. It is found that the spin echo peaks generally correspond to wall signals but not to domain signals in these compounds. The hyperfine field at Co nuclei in domains and the spacing between the quadrupole-split component lines for the domain signals are derived. The effect of substitution of Gd for Y on the Co hyperfine field and the magnetic exchange interaction between Co magnetic moments in the compounds is discussed.
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Hitoshi Ohta, Nobuyasu Yamauchi, Mitsuhiro Motokawa, Masaki Azuma, Mik ...
1992 年 61 巻 9 号 p.
3370-3376
発行日: 1992/09/15
公開日: 2007/05/29
ジャーナル
認証あり
ESR experiments on powder samples of SrCuO
2 and Sr
2CuO
3 have been tried in the submillimeter wave region. No resonance absorption has been observed on freshly prepared samples at the temperatures from 86 K to 265 K, while the samples left in the air for a few months have revealed distinct magnetic resonance signals around
g=2. Especially the complicated line shape of Sr
2CuO
3 suggests the overlap of two kinds of EPR, one of which is related to the EPR observed in SrCuO
2. From the results of H
2O gas exposed samples, the effect of H
2O to these samples is discussed.
抄録全体を表示
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Yoshihiro Ishibashi
1992 年 61 巻 9 号 p.
3377-3384
発行日: 1992/09/15
公開日: 2007/06/01
ジャーナル
認証あり
Domain walls between the incommensurate and commensurate regions are considered on the basis of a thermodynamic potential. It has turned out that there is a unique wall structure which minimizes the wall energy. By utilizing the results obtained, a mechanism of the transient processes between the incommensurate and the commensurate states is discussed, criticizing a previously proposed transient mechanism based upon a “particular” thermodynamic potential.
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Eisuke Iguchi, Keisuke Akashi
1992 年 61 巻 9 号 p.
3385-3393
発行日: 1992/09/15
公開日: 2007/05/29
ジャーナル
認証あり
Dielectric properties and dc-conductivities in p-type NiO doped with Li (1∼10 atomic%) were investigated below 300 K. Around 40 K, a dielectric relaxation peak appeared with an activation energy of 0.051 eV and the intensity of this peak was found to be thermally activated, the activation energy being 0.01 eV. There was a linear relation between log (σ
T3⁄2) and 1⁄
T in the range of ∼45 to ∼90 K and the activation energy was 0.057 eV. These behaviours have been discussed in terms of hopping process of nonadiabatic small polarons. The theoretical estimates of electron-phonon-coupling constants, λ, and the changes in spacings between ions,
x, associated with formation of a polaron have been carried out. The calculations yield λ and
x between Ni
3+ and Ni
2+ in 〈110〉 directions are −3.48 eV/Å and −9.6×10
−3 Å and these between Ni
3+ and O
2− in 〈100〉 directions are 0.42 eV/Å and 5.12×10
−2 Å. This theoretical calculation provides an evidence on stability of nonadiabatic small polarons in p-type NiO.
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Kazuo Gesi
1992 年 61 巻 9 号 p.
3394-3399
発行日: 1992/09/15
公開日: 2007/05/29
ジャーナル
認証あり
Dielectric properties of deuterated dicalcium double propionates, Ca
2Pb-(C
2D
5COO)
6 (DDLP) and Ca
2Pb(C
2D
5COO)
6 (DDBP), have been studied. The I–II (the Curie temperature) and II–III transition temperatures of annealed DDLP crystal are 313.1 K and 172 K, respectively. They are 14∼20 K depressed by deuteration. The isotope effect on DLP is much conspicuous in comparison with that of Ca
2Sr(C
2H
5COO)
6 (DSP). The temperature dependence of spontaneous polarization in DDLP is measured and compared with that of Ca
2Pb(C
2H
5COO)
6 (DLP). The I–II and II–III transition temperatures of DDBP are 275 K and 204.5 K, respectively. The deuteration causes an increase of about 8 K in the I–II transition temperature, but does not change virtually the II–III one.
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