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Tetsuo Nakanishi, Keizo Yamamoto
1992 年 61 巻 10 号 p.
3421-3424
発行日: 1992/10/15
公開日: 2007/06/01
ジャーナル
認証あり
A computational method is introduced for calculating coarse-grained stationary distributions of stochastic systems formulated by the master equation. By coarse-graining the state space, it becomes possible to enlarge the size of systems without increasing the number of calculation procedures. As a result, we will be free from the difficulty of the limitation on the system size. Therefore the method makes it practicable to numerically analyze statistical properties of nonlinear stochastic systems large enough for appraising the state of systems in the thermodynamic limit. Furthermore, it becomes easy to study the spatial structure of fluctuations of stochastic systems.
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Hideaki Ujino, Kazuhiro Hikami, Miki Wadati
1992 年 61 巻 10 号 p.
3425-3427
発行日: 1992/10/15
公開日: 2007/06/01
ジャーナル
認証あり
The integrability of the quantum Calogero-Moser model is proved through the quantum inverse scattering method. By use of the Lax operator
L, a new formula for the conserved operators is found. The formula suggests that Tr
Ln, which are conserved in the classical case, are not necessarily conserved operators. The Hénon-type conserved operators are also presented.
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Masaya Ishida, Hiromu Kato, Naokatu Sano, Hikaru Terauchi
1992 年 61 巻 10 号 p.
3428-3431
発行日: 1992/10/15
公開日: 2007/06/01
ジャーナル
認証あり
Generalized Fibonacci lattices which are generated by the inflation transformation
A→
AmB and
B→
A with integer
m, have been grown by means of molecular beam epitaxy. Many sharp satellite peaks are observed in the diffraction patterns, and the peaks are specified by γ(
m)=[
m+(
m2+4)
1⁄2]⁄2. When the ratio of alternating layer thicknesses (
dA⁄
dB) is equal to γ(
m), the intervals of peaks are indexed by only
q1γ(
m)
s with adequate
q1 and integer
s. When the value of
dA⁄
dB is not equal to γ(
m), the intervals of peaks are indexed by
q2γ(
m)
u and
q3γ(
m)
v with integers
u and
v (
q2≠
q3). The correlation of lattice arrangements becomes weaker with increasing
m, but the correlation is independent of sample size
N of the lattice.
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Masaru Kasahara, Pho Kaung, Toshirou Yagi
1992 年 61 巻 10 号 p.
3432-3435
発行日: 1992/10/15
公開日: 2007/06/01
ジャーナル
認証あり
Raman scattering from single crystals of K
3H(SO
4)
2 and its deuterated analogues has been observed at 295 and 45 K. The spectra do not depend on the scattering geometries. Scarcely any effect of deuteration on frequencies was noted for most of the Raman lines. The Raman lines of the internal modes split into two peaks in the ordered phase of DKHS. The splitting is attributed to the ordering of deuterons.
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Sadamitsu Harada, Makoto Iwata, Yoshihiro Ishibashi
1992 年 61 巻 10 号 p.
3436-3438
発行日: 1992/10/15
公開日: 2007/05/29
ジャーナル
認証あり
The temperature dependence of the elastic constant in [N(CH
3)
4]
2ZnBr
4 single crystal, which undergoes a ferroelastic phase transition at 288 K, was measured above the transition temperature. Results are discussed in terms of a Landau-type free energy.
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Tetsuro Saso
1992 年 61 巻 10 号 p.
3439-3442
発行日: 1992/10/15
公開日: 2007/06/01
ジャーナル
認証あり
The possibility of Kondo singlet state formation of a magnetic impurity in an insulator with a small gap is investigated by 1/
N expansion and the quantum Monte Carlo method. The former gives the criterion
Eg<2
TK for the singlet state formation, where
Eg and
TK denote the gap width and the Kondo temperature in the gapless case, and
Eg>2
TK for the magnetic state. The latter, applied to the Anderson model, demonstrates the crossover between the singlet and the magnetic states at a critical value of
Eg consistent with the above.
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Katsuhiko Takegahara, Yukihiro Shimizu, Osamu Sakai
1992 年 61 巻 10 号 p.
3443-3446
発行日: 1992/10/15
公開日: 2007/06/01
ジャーナル
認証あり
We study magnetic properties of a single-impurity Anderson model in the symmetric case, in which the density of states for conduction electrons vanishes in a finite energy gap containing the Fermi energy. A quantum Monte Carlo simulation at finite temperatures and low-energy excitations calculated by a numerical renormalization group method reveal that at low temperatures the impurity magnetic susceptibility follows Curie’s law. This behavior is consistent that the ground state is a doublet. The low-temperature Curie constant decreases monotonically with decreasing energy gap and the critical point is the zero gap. In the narrow gap limit, the impurity g-value of the doublet state is proportional to the gap width. This situation is due to the special feature of the symmetric case.
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Tadao Kasuya, Yoshinori Haga, Takashi Suzuki, Yasunori Kaneta, Osamu S ...
1992 年 61 巻 10 号 p.
3447-3451
発行日: 1992/10/15
公開日: 2007/05/29
ジャーナル
認証あり
On the basis of band calculation, the
p-
f mixing parameters and the spin-orbit splittings in La-monopnictides are evaluated, and temperature and pressure dependence of carrier number in Ce-monopnictides are studied. It is shown that in La-monopnictides the strongly correlated electron-hole pair effect is important, while in Ce-monopnictides the occupied bonding 4
f level near the Fermi level plays the most important role in the pressure effect. However, the electron-hole weak pair effect is dominant for the temperature dependence. Various anomalous properties are explained through the above model.
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Hidetoshi Fukuyama
1992 年 61 巻 10 号 p.
3452-3456
発行日: 1992/10/15
公開日: 2007/05/29
ジャーナル
認証あり
It is indicated that the stability of average valence +4⁄3 of Cu, i.e. Cu
+4⁄3, in various (DCNQI)
2Cu salts is the consequence of strong correlation at Cu sites. It is also discussed that the phase diagram separating metallic and insulating states together with the reentrance on the plane of pressure and temperature can be understood as due to the competition between the three-dimensionality and the Peierls instability associated with charge fluctuation of 4
kF as well as ordinary 2
kF in each chain.
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Haruyoshi Aoki, Shinya Uji, Ariane Keiko Albessard, Yoshichika \={O}nu ...
1992 年 61 巻 10 号 p.
3457-3461
発行日: 1992/10/15
公開日: 2007/05/29
ジャーナル
認証あり
We have observed a new de Haas-van Alphen (dHvA) oscillation in CeRu
2Si
2 of frequency 5.36×10
7 Oe and cyclotron effective mass 120
m0 for magnetic fields along the [100] direction. The new dHvA frequency is thought to arise from the heavy electrons of the large hole surface centered at the
Z point which is predicted by the band structure calculations.
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Hiroshi Kohno, Hideo Yoshioka, Hidetoshi Fukuyama
1992 年 61 巻 10 号 p.
3462-3465
発行日: 1992/10/15
公開日: 2007/06/01
ジャーナル
認証あり
Bismuth has been known to exhibit anomalously large diamagnetism which has been interpreted on the basis of the effective Hamiltonian of the Dirac type including spin-orbit coupling. Here the persistent current in a mesoscopic ring of bismuth is calculated. It is found that the magnetic flux induces persistent currents which have a spatial spread of the order of ξ=2h
v⁄
EG (
v: velocity of the ‘Dirac’ electron;
EG: energy gap), just as in the atomic diamagnetism whose “atomic” size is gigantic and of mesoscopic scale.
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Yositake Takane, Hiromichi Ebisawa
1992 年 61 巻 10 号 p.
3466-3469
発行日: 1992/10/15
公開日: 2007/06/01
ジャーナル
認証あり
Low-bias conductance of impure normal-superconductor contacts is studied theoretically in the limit of the small Andreev reflection probability. Its dependence on both magnetic field and temperature is obtained. In the calculation, we focus our attention on the interference effect between an electron and a hole that is suggested to be significant by van Wees
et al. It is shown that the conductance is sensitively suppressed by a magnetic field or temperature.
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Hiroyuki Deguchi, Masakazu Itoh, Kazuyoshi Takeda
1992 年 61 巻 10 号 p.
3470-3473
発行日: 1992/10/15
公開日: 2007/05/29
ジャーナル
認証あり
The characteristic temperature dependence of heat capacity
C has been observed in a
S=1 Haldane-gap system (CH
3)
4NNi(NO
2)
3 (TMNIN) at low temperatures. In zero external field, the data of
C below 2 K fit the equation
C=
AT−2 exp (−
Δ⁄
kBT), where the gap energy is
Δ⁄
kB=4.2 K. As the external field increases to 30 kOe, the value of the gap energy
Δ becomes smaller and the heat capacity
C comes to depend nearly linearly on the temperature
T. A cooling phenomenon has been found in the process of adiabatic magnetization at low temperatures, which is most enhanced for the applied field just above 33 kOe. These results are consistent with the existence of the Haldane gap.
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Tsukasa Ishii, Mitsugu Matsushita
1992 年 61 巻 10 号 p.
3474-3477
発行日: 1992/10/15
公開日: 2007/06/01
ジャーナル
認証あり
Fragment-size and -mass distributions of long, thin glass rods (1500 mm long and 2 mm diameter) are studied experimentally by dropping horizontal glass rods. At lower falling height (about 1 m drop), they can be described by the lognormal distribution. With increasing falling height, the distributions start to exhibit a power-law form. At falling heights greater than about 4.5 m, the power-law form becomes stable with an almost fixed exponent. The distibutions also show clear crossover to three-dimensional fracture of glass rods around the rod diameter.
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Tsutomu Kawata
1992 年 61 巻 10 号 p.
3479-3487
発行日: 1992/10/15
公開日: 2007/06/01
ジャーナル
認証あり
The dressing method (
DM) powerful for the local analysis of some integrable systems and the inverse spectral transform (
IST) are compared for the case of an eigenvalue problem in 2×2-matrix order and 1+1 dimensions. Although the solution method of
DM is reduced to Gel’fand-Levitan type of integral equations (
GLE), that is not excatly equivalent to the one obtained by the
IST. This problem was studied particularly and we found that the principal factorization formula as to the Fredholm type of operators used in the
DM is directly related with the Riemann-Hilbert problem (
RHP) which is important for the
IST.
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Kiyomi Okamoto
1992 年 61 巻 10 号 p.
3488-3493
発行日: 1992/10/15
公開日: 2007/06/01
ジャーナル
認証あり
The effect of bond alternation in the
Sz−
Sz coupling (
z-alternation) on the dimerization in an
S=1⁄2 Heisenberg chain is investigated both analytically and numerically. The spin Hamiltonian is transformed into the phase Hamiltonian, and the variational method is used. An analytical study shows that the
z-alternation plays an important role and brings about the dimerization when there is no bond alternation in the
Sx−
Sx and
Sy−
Sy couplings. The results of numerical diagonalization for finite systems support the above analytical conclusion.
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Tota Nakamura, Naomichi Hatano, Hidetoshi Nishimori
1992 年 61 巻 10 号 p.
3494-3502
発行日: 1992/10/15
公開日: 2007/05/29
ジャーナル
認証あり
We propose a new method for quantum Monte Carlo simulations with the negative-sign problem. In the conventional method, one simulates a virtual system whose Boltzmann factors are the absolute values of the original one, and analyzes the data so that the correct expression for physical quantities may be recovered. We simulate a different virtual system with properties closer to the original system and yet without the negative-sign problem. Comparison between the present method and the conventional one is made for the antiferromagnetic Heisenberg model on the 4×4 square lattice with frustrations (
J1-
J2 model). We conclude that the present method is useful in the low-temperature region where the negative-sign problem becomes serious. It is also shown that the method is considerably efficient on the point that quantities for different parameters can be obtained in a single run.
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Macoto Kikuchi, Yutaka Okabe
1992 年 61 巻 10 号 p.
3503-3510
発行日: 1992/10/15
公開日: 2007/06/01
ジャーナル
認証あり
The order-parameter distribution functions (OPDF) of the ferromagnetic three-state Potts model in
d=2 and 3 are studied by means of the Monte Carlo simulation. We investigate the difference between the behavior of OPDF for the vector order parameter and that for the scalar order parameter. The OPDF for the scalar order parameter show a double-peak structure not only at the first-order phase transition but also at the second-order one. The origin of the above fictitious double-peak structure, which does not appear in OPDF for the vector order parameter at the second-order transition, is discussed in connection with the structure of the order-parameter space.
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Tomoyuki Nagaya, Hideki Hotta, Hiroshi Orihara, Yoshihiro Ishibashi
1992 年 61 巻 10 号 p.
3511-3517
発行日: 1992/10/15
公開日: 2007/06/01
ジャーナル
認証あり
Dynamics of interactive disclinations in a nematic liquid crystal cell, which can be regarded as the two-dimensional XY-system, has been investigated. We made numerous wedge disclinations of the strength ±1 and observed the annihilation process by means of a polarizing microscope. By analyzing the image, it is found that the number of disclinations
N(
t) decreases as
N(
t)∼
t−1 and the dynamical scaling law holds. Furthermore, the correlation function obtained by experiments is discussed by applying the theory of the two-dimensional XY-model.
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G. P. S. Sahota, Harjinder Singh, H. S. Binarh, B. S. Pallah, H. S. Sa ...
1992 年 61 巻 10 号 p.
3518-3523
発行日: 1992/10/15
公開日: 2007/06/01
ジャーナル
認証あり
An X-ray fraction, efficiency and fluorescence yield independent method has been developed for the measurement of
K-capture probabilities to the 437, 384, 161 and 81 keV levels in
133Cs from the EC decay of
133Ba. With errors minimised, the results are more precise compared with earlier works.
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Anita Pandita, H. M. Agrawal
1992 年 61 巻 10 号 p.
3524-3534
発行日: 1992/10/15
公開日: 2007/06/01
ジャーナル
認証あり
The fluctuations of the
s-wave neutron reduced widths for many nuclei have been analyzed with emphasis on recent measurements by a statistical procedure which is based on the method of maximum likelihood. It is shown that the
s-wave neutron reduced widths of nuclei follow single channel Porter Thomas distribution (
x2-distribution with degree of freedom ν=1) for most of the cases. However there are apparent deviations from ν=1 and possible explanation and significance of this deviation is given. These considerations are likely to modify the evaluation of neutron cross section.
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Yasufumi Susuki, Takashi Ito, Kenji Kimura, Michi-hiko Mannami
1992 年 61 巻 10 号 p.
3535-3546
発行日: 1992/10/15
公開日: 2007/06/01
ジャーナル
認証あり
Angular and energy distributions of scattered fragments have been measured at glancing angle incidence of MeV HeH
+ ions on a clean (001) surface of SnTe crystal. The distributions show that the internuclear vectors between fragments tend to align with the beam direction and the kinetic energy of the fragments acquired by the dissociation is smaller than that released at He
2+–H
+ explosion. The alignment of the internuclear vectors is explained in terms of a surface wake potential due to dynamic response of surface electrons to the charges of fragments. The observed kinetic energy indicates that most of the HeH
+ ions are excited to some excited states without loss of electrons and dissociate into pairs of He and H ions on the incoming trajectories and the loss of electrons of the fragments does not occur until the internuclear distance of the pairs becomes a few times of the ground state one.
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Takashi Ishihara, Yukio Kaneda
1992 年 61 巻 10 号 p.
3547-3558
発行日: 1992/10/15
公開日: 2007/06/01
ジャーナル
認証あり
A study is made of the stretching and distortion of material line elements in turbulence both analytically and numerically. Approximations for the statistics of these processes derived by perturbative expansions are tested by comparison with dynamical simulations in two dimensions. An integral time scale associated with the Lagrangian statistics of the velocity gradients plays a key role in the approximations. A rough estimation of the time scale is obtained by a dynamical short-time analysis by making use of the Navier-Stokes equation.
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Hiroaki Ono
1992 年 61 巻 10 号 p.
3559-3565
発行日: 1992/10/15
公開日: 2007/06/01
ジャーナル
認証あり
Taking gravity wave train as an example, the effect of gentle and weak inhomogeneity on nonlinear steady waves governed by the nonlinear Schrödinger equation in homogeneous media is investigated. It is shown that this kind of inhomogeneity causes deformation but neither damping nor amplification of such waves during propagation, which presents a striking contrast to the case of finite inhomogeneity; for instance, the case of finite variation of the water layer depth. Further it is shown that, when the inhomogeneity is stochastic, the center of mass of the nonlinear steady wave performs a random walk and their averaged amplitudes diffuse algebraically and, on the other hand, that the averaged carrier waves diffuse exponentially even due to much weaker inhomogeneity.
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Kazuo Minami, Md. Mortuza Ali, Kazuo Ogura, Wonsop Kim, Tuguhiro Watan ...
1992 年 61 巻 10 号 p.
3566-3575
発行日: 1992/10/15
公開日: 2007/06/01
ジャーナル
認証あり
Starting current conditions for initiating radiation from a backward oscillator with finite structure length and with non-zero end reflections are analyzed numerically. Because of the leak of radiation at both ends, the beam starting current for initiating oscillation cannot be zero. Various models for computing the condition are compared and discussed from the stand point of actual experiments.
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Shigehiko Nonaka
1992 年 61 巻 10 号 p.
3576-3586
発行日: 1992/10/15
公開日: 2007/06/01
ジャーナル
認証あり
Contributions of negative and positive ions to planar radio-frequency (RF) plasmas produced by an even surface wave (SWP) traveling between a pair of semi-infinite two dielectric regions are investigated theoretically by solving a quasistatic Laplace equation. In this theory, the first-order approximation with respect to the wave attenuation is employed to obtain the results; (I) the density of the produced plasma decreases almost linearly with the wave propagation, (II) the produced plasma length extends longer due to the ion contributions, and (III) several fundamental characteristics for the surface wave, such as RF power flow, wave potential and electric fields, were also clarified relating to the ion contributions.
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Mieko Toida, T. X. Zhang, Yukiharu Ohsawa
1992 年 61 巻 10 号 p.
3587-3592
発行日: 1992/10/15
公開日: 2007/05/29
ジャーナル
認証あり
The structure of a nonlinear magnetosonic wave in a multiple-ion-species plasma is analytically investigated, and the elemental composition of ions reflected by the magnetosonic wave is studied. Firstly, stationary solutions of magnetosonic waves propagating perpendicularly to a magnetic field in a plasma consisting of electrons and two-species ions are obtained from a fluid model. Secondly, on the basis of the solitary wave solution, conditions for ion reflection are discussed. Then, the fraction of high-energy ions produced by a magnetosonic wave is expressed in terms of the ion mass, charge, thermal speed, Alfvén speed, and wave amplitude. It rapidly decreases with increasing mass. It is found that most of the light ions can be reflected in a multiple-ion-species plasma even for small-amplitude waves if the masses of the main component ions are sufficiently heavy.
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Kazuyuki Itoh, Akira Niwata, Wataru Abe, Hirofumi Kasatani, Eiji Nakam ...
1992 年 61 巻 10 号 p.
3593-3600
発行日: 1992/10/15
公開日: 2007/06/01
ジャーナル
認証あり
Ferroelectric phase transition in DLP crystals is studied on the basis of the crystal structure determined at various temperatures above and below the phase transition temperature. Temperature variation of the atomic order parameter of methyl groups is determined. In contrast to the disordered character in the CH
3 groups, the ionic atoms; Pb, Ca and O, which bear the major part of spontaneous polarization, exhibit no disordered character in both phases. It is pointed out that the disordering in the CH
3 groups is by no means strongly correlated with motions of ionic atoms in view of quite a special atomic arrangement of DLP. We discuss that this weak coupling between two structural parts leads to the well known peculiar nature of the DSP-type crystals.
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Yoichi Kawase, Sin-ichi Uehara, Saburo Nasu
1992 年 61 巻 10 号 p.
3601-3605
発行日: 1992/10/15
公開日: 2007/05/29
ジャーナル
認証あり
The time-differential perturbed angular correlation(TDPAC) technique has been applied to study the microcrystalline structure of indium metal near the melting point with
111In radioactive probes. The TDPAC function observed at 155°C just below the melting point (156.4°C) indicates the formation of a partially oriented matrix in a polycrystalline lattice.
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Hideshi Fujishita
1992 年 61 巻 10 号 p.
3606-3612
発行日: 1992/10/15
公開日: 2007/06/01
ジャーナル
認証あり
Crystal structure of intermediate phase of PbZrO
3 was analyzed by neutron powder diffraction. Superlattice reflections of our sample appeared at
M and
R points. Intensities of fundamental reflections also changed in the phase. The structural modulations were associated with modes either
Γ15+
M3+
R25 or
Γ15+
M5′+
R25. The modulation associated with the
R25 mode of our sample might be caused by an extrinsic origin. Dielectric constant was also measured and a mechanism of the phase transitions is discussed briefly.
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Junichi Aoyama, Shigeo Suzuki, Mieko Takagi
1992 年 61 巻 10 号 p.
3613-3624
発行日: 1992/10/15
公開日: 2007/06/01
ジャーナル
認証あり
Antiparallel domain walls of ferroelectric thiourea have been observed on X-ray diffraction topographs. These domain walls are (001) planes with thicknesses less than 1 μm. Contrast of the images of the walls on the topographs depends on the kind of Bragg reflections used for the topographs. This dependence indicates that the structure of the domain walls is similar to the intermediate phase with modulated long period structures (phase II′ and phase IV) observed between the high temperature paraelectric phase and low temperature ferroelectric phase. A Bragg reflection from the domain walls accompanies satellite reflections. The period of the modulated structure of the walls is estimated to be 300∼500 times the length of the
c-axis of the ferroelectric phase.
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Kazuaki Iwasa, Nobuyoshi Wakabayashi, Masamichi Sakai, Noritaka Kuroda ...
1992 年 61 巻 10 号 p.
3625-3630
発行日: 1992/10/15
公開日: 2007/06/01
ジャーナル
認証あり
The halogen-bridged transition metal complex [Pt(en)
2][PtCl
2(en)
2](ClO
4)
4 has a quasi-one dimensional structure with Pt ions forming chains along the
b-axis. The valence of the Pt ions can have two possible values, II and IV, and is disordered. Diffuse X-ray scattering was found for wavevectors around (0 2
n+1 0). The intensity distribution along the (0 1 0) was very narrow, while that for wavevectors perpendicular to (0 2
n+1 0) showed clearly the existence of a short range order between the valence sequences of neighboring chains. A strong correlation has been found between the chain at the origin and one at the second neighbor position along the
c-axis. The results were analyzed in terms of interchain interactions.
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Minoru Takeda, Kazu Nishigaki
1992 年 61 巻 10 号 p.
3631-3635
発行日: 1992/10/15
公開日: 2007/06/01
ジャーナル
認証あり
Using a capillarity method and a split type superconducting magnet, the surface tension of liquid oxygen has been measured in various magnetic fields up to 5 T at 65.3 K and 77.1 K. Experimental data are compared with the numerical calculations obtained on the basis of the theory of surface tension. It is found that the dependence of surface tension on magnetic field is so small that it can not be the main cause of the shape deformation of the meniscus.
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Tadeusz Luty
1992 年 61 巻 10 号 p.
3636-3642
発行日: 1992/10/15
公開日: 2007/06/01
ジャーナル
認証あり
The neutral-ionic transformation in mixed-stack organic charge-transfer (CT) crystals has been analysed within a phenomenological theory. The theory uses two parameters: lattice distortion (the stack dimerization) which breaks inversion symmetry and molecular deformation (related to molecular ionicity) which preserves site symmetry. A coupling of totally symmetric molecular vibrations with a charge-transfer between donor and acceptor molecules allows to introduce the concept of molecular compressibility which includes both elastic and electronic contributions. The concept helps to understand discontinuity of the neutral-ionic transformation and can be usefull in the theory of solid state chemistry.
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Takashi Odagaki
1992 年 61 巻 10 号 p.
3643-3650
発行日: 1992/10/15
公開日: 2007/06/01
ジャーナル
認証あり
The hyperinflation technique is shown to be an efficient way to obtain the energy bands, the density and integrated density of states for a tight-binding electron in one-dimensional quasicrystals and their approximants. Within the semiclassical treatment of a carrier dynamics, the approximant crystals are shown to exhibit negative differential conductivity for sufficiently strong fields.
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Tomotoshi Nishino
1992 年 61 巻 10 号 p.
3651-3657
発行日: 1992/10/15
公開日: 2007/06/01
ジャーナル
認証あり
The author investigates the one-dimensional extended Hubbard model, i.e. the Hubbard model with additional nearest neighbor Coulomb repulsion
V. The charge excitation gap at half-filling is obtained numerically. The calculated gap is smaller than that given by the Hartree-Fock approximation, especially near the phase boundary. The gap is finite at the boundary when
U=12, the result which gives an upper bound for the position of the tricritical point.
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Tsuyoshi Yamaguchi
1992 年 61 巻 10 号 p.
3658-3677
発行日: 1992/10/15
公開日: 2007/05/29
ジャーナル
認証あり
Electronic states of the 2×1 terrace, the unreconstructed S
a, buckled S
a, reconstructed S
b and unreconstructed S
b steps under electric fields parallel to the Si(001) surface are calculated by the DV–Xα–LCAO method. If an electric field is applied in parallel and perpendicular to dimers, electron transfer between neighboring atoms of two dimers is larger and smaller, respectively. For both S
a and S
b steps, electric field induces large electron transfers between dimers on the higher and lower terraces near the step edge. Furthermore, it changes the charge density of valence bonds between surface and subsurface atoms near the step edge. For the S
a steps, electric field applied in the step-down (-up) direction induces a large shift of energy levels to the lower (higher) energy side. For the S
b steps, electric field induces a shift of energy levels in opposite direction to that of the S
a steps.
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Bunjyu Shinozaki, Takasi Kawaguti, Yasunobu Fujimori
1992 年 61 巻 10 号 p.
3678-3688
発行日: 1992/10/15
公開日: 2007/06/01
ジャーナル
認証あり
In order to investigate the pair-breaking mechanism in superconducting films superposed with thin normal metal (Au, Ag, or Cu), the inelastic electron scattering rate 1/τ
in and the spin-orbit scattering rate 1/τ
so have been studied for aluminum films. The rate 1/τ
in has been expressed as a sum of three rates 1/τ
fluc (electron-fluctuation), 1/τ
e-e (electron-electron) and 1/τ
e-ph (electron-phonon). It has been found that 1) the effect of superposition on each rate depends on the superposed metals and on preparation conditions of Al film; 2) the rate 1/τ
in determines essentially the pair-breaking parameter δ in the Maki-Thompson term for excess conductance, although 1/τ
so increases more strongly with heavier superposed metal; and 3) the increment of δ observed in Al/Au films is caused by the enhancement of 1/τ
fluc.
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Kunihiko Yamaji, Kikuo Harigaya, Takashi Yanagisawa, Yukihiro Shimoi
1992 年 61 巻 10 号 p.
3689-3698
発行日: 1992/10/15
公開日: 2007/06/01
ジャーナル
認証あり
By means of the exact-diagonalization method we have studied the finite-size two-band model with the interband pair-transfer interaction by calculating the superconducting (SC) correlation function
Ps etc. in the ground state. Occurrence of SC was clearly indicated by the increase of
Ps. The diagram of the observed SC region was constructed in the plane of the relative position of the second band versus on-site Coulomb energy
U. In the low-density limit it proved close to the region where a negative-
U situation is realized by the pair-transfer interaction. On the high-density side, the SC region was found to be more extended than the latter in accord with the previous interband-ladder-diagram results. Inclusion of the exchange interaction was found to reduce the SC region in a restricted region where two bands substantially share electrons. The two-band situations in cuprates are argued to be relevant to the high
Tc through the present mechanism.
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Shigeyuki Murayama, Hironori Inaba, Kensuke Hoshi, Yoshihisa Obi
1992 年 61 巻 10 号 p.
3699-3707
発行日: 1992/10/15
公開日: 2007/06/01
ジャーナル
認証あり
We have measured the magnetization and Mössbauer effect on vapor-quenched amorphous Hf
1−xTa
xFe
2 alloys prepared by sputtering for
x=0, 0.3, 0.5, 0.7, 0.9 and 1 from 4.2 to 300 K. We observed the spontaneous magnetization for all the present samples except for
x=1, where the ferromagnetic moment and Curie temperature monotonically decrease with increasing Ta concentration. A comparison between the ferromagnetic and paramagnetic moments suggests that the alloys are an itinerant-electron ferromagnet. The reduced low-temperature magnetization falls characteristically below that of crystalline HfFe
2 and follows a
T3⁄2 law. From the broad Mössbauer spectrum below the Curie temperature we estimate the average hyperfine field. Ta-concentration and temperature dependence of the average hyperfine field agrees with that of the magnetization.
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Hiroshi Shimahara
1992 年 61 巻 10 号 p.
3708-3720
発行日: 1992/10/15
公開日: 2007/06/01
ジャーナル
認証あり
The spin-fermion model on the CuO
2 lattice of the high temperature superconducting oxides (high-
Tc oxides) is studied by a perturbation theory. We require in our formulation that the sum rule of the spin correlation functions is satisfied, and that the rotational symmetry in the spin space are not broken. It is found that the spin wave velocity decreases with increasing hole concentration
nh. We find that the antiferromagnetic (AF) long-range-order (LRO) at zero temperature decreases linearly with doping holes near
nh=0 and finally vanishes with the infinite slope at critical hole concentration
nhc. An expression of the AF LRO for
nh≠0 and that of
nhc are obtained. The
nh dependence of the AF LRO is found to be very similar to those obtained in the two and three dimensional
t-
J models. We obtain semi-quantitative agreement with experimental results of the high-
Tc oxides as well as qualitative one. Validity of the perturbation approximation is discussed.
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K\={o}ki Takanashi, Yuzo Kamiguchi, Hiroyasu Fujimori, Mitsuhiro Motok ...
1992 年 61 巻 10 号 p.
3721-3731
発行日: 1992/10/15
公開日: 2007/06/01
ジャーナル
認証あり
Spin-flop and compensation phenomena of the magnetization in ferrimagnetic Fe/Gd multilayer films have extensively been investigated. It turns out that experimental results of the field and temperature dependence of magnetization agree fairly well with the calculated ones based on the molecular field model. In the calculation, we have obtained the magnetic structure, assuming that the composition is modulated stepwise, and that the exchange interactions in Fe and Gd layers are the same values as those in bulk Fe and Gd metals, respectively. Both longitudinal and transverse magnetoresistances show a crossover near the spin flop field due to the change in the magnetic structure. This crossover behavior is qualitatively well simulated by the calculation on the assumption of the parallel current flow in each atomic layer.
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Tsutomu Momoi, Masuo Suzuki
1992 年 61 巻 10 号 p.
3732-3744
発行日: 1992/10/15
公開日: 2007/06/01
ジャーナル
認証あり
Long-range order, especially chiral order, in the two-dimensional spin 1/2
XXZ antiferromagnet
H=
JΣ(
SixSjx+
SiySjy+
ΔSizSjz) on a triangular lattice is studied, partially by showing exact ground states and partially using the spin-wave theory. Exact ground states in the region
Δ≤−0.5 are found. These states are not disordered by quantum fluctuation. Most of the ground states at
Δ=−0.5 have a so-called 120° structure. Ground-state properties in the region −0.5≤
Δ≤1 are studied using the spin-wave theory. It is shown that quantum fluctuations are enhanced in the ground states as
Δ is increased. The phase diagram of the relevant system at low temperatures is also discussed using the spin-wave theory.
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Minoru Takahashi, Minoru Kinoshita, Masayasu Ishikawa
1992 年 61 巻 10 号 p.
3745-3751
発行日: 1992/10/15
公開日: 2007/06/01
ジャーナル
認証あり
Low-temperature magnetic properties of the γ-phase of
p-NPNN are analyzed by the mean-field theory based on the Bethe-ansatz solution of the one-dimensional ferromagnetic Heisenberg model. This substance consists of weakly interacting ferromagnetic chains with the intrachain coupling of 4.3 K. Using the low-temperature data we found that the interchain couplings are not purely ferromagnetic nor antiferromagnetic;
J′=0.224 K and
J″=−0.176 K. It is shown that the present theory reproduces the experimental results of this substance very well.
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Keiichi Ikegami, Shin-ichi Kuroda, Michio Sugi, Takayoshi Nakamura, Hi ...
1992 年 61 巻 10 号 p.
3752-3765
発行日: 1992/10/15
公開日: 2007/06/01
ジャーナル
認証あり
The ESR spectra of conductive Langmuir-Blodgett (LB) films of N-docosylpyridinium-(TCNQ)
2 are observed at the
X and
K bands. The spectrum simulation method is adopted to analyze these spectra, which show clear out-of-plane anisotropy, in order to obtain information concerning the magnetic and structural properties of the system. The analysis reveals that the linewidth anisotropy is dominated by the exchange-narrowed secular dipolar width peculiar to quasi one-dimensional spin systems. This result is consistent with the temperature dependent spin susceptibility data of the system, which has been found to be explained by the random-exchange Heisenberg antiferromagnetic chain model. These facts indicate the development of one-dimensional spin chains in the LB films. In addition, the orientation of TCNQ molecule is estimated from the spectrum analysis.
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Saburo Nasu, Marcel Miglierini, Keiichi N. Ishihara, Paul H. Shingu
1992 年 61 巻 10 号 p.
3766-3772
発行日: 1992/10/15
公開日: 2007/06/01
ジャーナル
認証あり
Mechanical grinding (MG) of icosahedral Al
65Cu
20Fe
15 quasicrystal has been performed by ball milling for up to 200 hours. Specimens, taken after different milling times, were examined by X-ray diffraction and transmission
57Fe Mössbauer spectroscopy. It is found that MG led to structural changes from quasicrystalline to amorphous phase. Two possible transformation mechanisms with the corresponding fitting models for evaluation of the Mössbauer spectra are proposed. The model consisting of two blocks of the P(
Δ) distributions of the electric quadrupole interaction is superior to that one which assumes only one P(
Δ) suggesting a creation of an amorphous phase and its gradual increase in the specimen’s volume during the ball milling of icosahedral quasicrystal.
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Makoto Honda, Makoto Morita, Muneyuki Date
1992 年 61 巻 10 号 p.
3773-3785
発行日: 1992/10/15
公開日: 2007/06/01
ジャーナル
認証あり
Electron spin resonance (ESR) and magnetic susceptibility of two chromium trimer complexes are investigated. Temperature dependence of magnetic susceptibility is well explained by antiferromagnetically coupled trimer model with two kinds of isosceles trimers in Cr-acetate and one isosceles trimer in Cr-propionate. A weak intertrimer exchange interaction is found in Cr-propionate. The angular dependences of ESR signals are satisfactorily explained by the trimer model. Anomalous negative
g-shift is observed in the field direction parallel to the trimer plane, which is attributed to the Dzyaloshinsky-Moriya interaction. A hybrid resonance of two doublets is found in Cr-acetate which is explained also by the Dzyaloshinsky-Moriya interaction.
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Hideaki Sakata, Katsumi Hamano
1992 年 61 巻 10 号 p.
3786-3793
発行日: 1992/10/15
公開日: 2007/05/29
ジャーナル
認証あり
Nematic liquid crystal technique, etching technique and powder technique have been applied to the study of the polarization reversal process in the commensurate-ferroelectric phase of K
2ZnCl
4. A single domain crystal undergoes polarization reversal through the sidewise expansion of domains nucleated at the predetermined locations in the bulk or at the crystal edges. The phase of the primary order parameters differs by π between the switched and unswitched regions, and the whole crystal is finally switched to a single domain. The polarization reversal process in a multidomain crystal is very complicated. The crystal can hardly be changed into a single domain state by the application of a dc field.
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Tomoyuki Hikita, Yasuhiro Ono, Akihiro Bungo
1992 年 61 巻 10 号 p.
3794-3798
発行日: 1992/10/15
公開日: 2007/06/01
ジャーナル
認証あり
Effect of hydrostatic pressure on the ferroelectric phase transition in KH
2AsO
4 is studied by dielectric measurements. The temperature at which the dielectric constant ε
C takes a peak value decreases with increasing pressure, and no peak is observed at 15.0 kbar. The anomaly of ε
C becomes broader with pressure. The transition temperature determined from the peak of ε
C is well represented by the equation
TC=
B(
pC−
p)
1⁄2 which is one of the manifestation of quantum ferroelectricity. Here, the critical pressure
pC is determined to be 14.8 kbar. Another critical behavior for the quantum ferroelectricity near the critical pressure (ε
C−ε
C∞)
−1=
DT2 is examined. It is found that ε
C at 14.5 kbar well represents this relationship.
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Eiji Hashimoto, Yoshitake Ueda, Nobuyuki Uematsu, Masayuki Iwami, Taka ...
1992 年 61 巻 10 号 p.
3799-3802
発行日: 1992/10/15
公開日: 2007/05/29
ジャーナル
認証あり
The experimental determination has been made on the specific trapping rate μ
d of a positron into dislocations in deformed aluminum (99.999% purity) at room temperature. A good linear relationship between the trapping rate and the dislocation density yields a value of (1.7±0.2)×10
−4 m
2 s
−1 for μ
d. A comparison with published values suggests that impurities may reduce the trapping rate even in trace amounts.
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