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Hitoshi Hojo, Tadatsugu Hatori, Syoichi Miyoshi
1990 Volume 59 Issue 3 Pages
789-791
Published: March 15, 1990
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Potential enhancement due to RF-induced parallel velocity space diffusion in a tandem mirror is studied by using a one-dimensional model based on the linearized Fokker-Plank equation with a quasi-linear RF diffusion term. A modified Boltzmann relation between the plasma density and the confining potential is obtained as a function of the RF diffusion coefficient under the assumption of small deviation from the Maxwellian for distribution function. The relation shows that the confining potential increases with the increase of the RF diffusion coefficient. The confining potential is saturated for the flat distribution function in the limit of strong RF diffusion.
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Kenichi Kojima, Yusuke Nakai, Takashi Suzuki, Hajime Asano, Fujio Izum ...
1990 Volume 59 Issue 3 Pages
792-795
Published: March 15, 1990
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The crystal structure of YbInCu
4 has been refined by the Rietveld analysis of TOF neutron powder diffraction data. This compound has a cubic AuBe
5 (C15b, F\bar43m)-type structure with the lattice constant
a=7.1575(6) Å, and Yb ions are completely ordered at the 4c site. X-ray powder diffraction data have also been taken as a function of temperature. The lattice constant shows an abrupt change of 0.15% at the temperature of Yb valence phase transition (about 40 K) without any change in the crystal symmetry.
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Tetsushoku Tei, Kaoru Kimura, Shin Takeuchi
1990 Volume 59 Issue 3 Pages
796-799
Published: March 15, 1990
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We have constructed a model structure of Frank-Kasper-type icosahedral quasicrystals based on the 3-D Penrose lattice which is decorated according to Henley and Elser (Philos. Mag. B
53 (1986) L59), and relaxed by interatomic potentials. Calculated (partial) pair correlation functions of the model agree well with the experimental ones in literature.
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Yoshihiro Ishibashi
1990 Volume 59 Issue 3 Pages
800-802
Published: March 15, 1990
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The temperature-concentration phase diagram of a high-
Tc superconductor La
2−xBa
xCuO
4 system is reproduced satisfactorily with the use of a Landau-type thermodynamic potential, where a sixth-order term in the transition parameters is taken into account.
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Gendo Oomi, Yoshichika \={O}nuki, Takemi Komatsubara
1990 Volume 59 Issue 3 Pages
803-806
Published: March 15, 1990
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The thermal expansion of single-crystalline CeCu
6 and LaCu
6 has been measured by using the strain gauge method in the temperature range from 6 K to 300 K. A large anisotropy was found in the temperature dependence of thermal expansion (
Δl⁄
l)
i (
i denotes the crystal axis,
i=
a,
b and
c). The contribution of the 4f electron to thermal expansion is very large for the
b-axis and extremely small for the
a-axis. The thermal expansion coefficient α was also estimated from these data. An anomalous enhancement in the α
l⁄
T vs
T2 plot (α
1=1⁄3 (α
a+α
b+α
c)) was found at low temperature below about 20 K, which is considered to correspond to the large enhancement of the
C⁄
T value at low temperatures where
C is the specific heat. These results are discussed in connection with other heavy fermion materials.
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Hidetoshi Fukuyama, Osamu Narikiyo, Kazuhiro Kuboki
1990 Volume 59 Issue 3 Pages
807-810
Published: March 15, 1990
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The extended
t-
J model, which has both transfer integral and exchange interaction between next-nearest neighbors besides those between nearest neighbors, has been investigated by the mean field approximation in the slave-boson scheme. Especially, the staggered flux state and the chiral spin state have been investigated. For the latter state, anyons are derived by use of the result of the Chern-Simons term for the doped case. It is shown that the prefactor of the Chern-Simons term and thus the fractional statistics depend on the degree of doping.
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Hisashi Hiramoto
1990 Volume 59 Issue 3 Pages
811-814
Published: March 15, 1990
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The effect of an interelectron interaction (
U) on electronic properties in one-dimensional quasiperiodic systems (the incommensurate Harper model and the Fibonacci model) is studied within the Hartree-Fock (HF) approximation. For the Fibonacci model, the HF one-body spectrum remains singular continuous (critical wave functions) for small |
U|. For the Harper model, on the other hand, the singular continuous spectrum at critical coupling (λ
c=2) disappears as soon as
U is added.
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Yasuhiro Seino, Akio Kotani, Antonio Bianconi
1990 Volume 59 Issue 3 Pages
815-818
Published: March 15, 1990
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We theoretically study the polarization dependence of the Cu 2
p-XAS (X-ray absorption spectrum) in high
Tc superconductors with the use of a simple CuO
4 cluster. We take account of both the Cu 3
d(
x2−
y2) and 3
d(3
z2−
r2) orbitals, and study the effect of a possible rhombic distortion by which the two 3
d orbitals are mixed with each other. The polarized XAS is calculated both in the undoped “Cu
2+” system and the hole-doped “Cu
3+” system. A considerably large intensity ratio between
E⁄⁄
c and
E⊥
c absorption spectra is obtained in the “Cu
3+” system as a result of the rhombic distortion, where
E and
c are directions of the X-ray electric field and the crystalline
c-axis, respectively. These results help to explain the increase in the polarized
E⁄⁄
c Cu 2
p-XAS white line going from the insulating to the hole-doped phases in Bi–Sr–Ca–Cu–O (2212) systems.
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Jun Kondo
1990 Volume 59 Issue 3 Pages
819-821
Published: March 15, 1990
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It is shown that the ordering of oxygen found in the basal plane of YBa
2Cu
3O
6.5 can be explained in terms of the long-range Coulomb interaction between the oxygen ions, the ionization potential of copper and the electron affinity of oxygen. Furthermore, it is shown that the ordering induces self-doping and creates holes in the CuO
2 planes even though the nominal hole content of this substance is zero.
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Yasumasa Hasegawa, Osamu Narikiyo, Kazuhiro Kuboki, Hidetoshi Fukuyama
1990 Volume 59 Issue 3 Pages
822-825
Published: March 15, 1990
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Anyons are constructed in the commensurate flux phases in the
t-
J model using slave boson mean-field theory. Fluctuations of the local constraint and the mean-field order parameters, which couple to both fermions and slave bosons, are treated as the gauge field. The coupling to the fermion creates the Chern-Simons term for the gauge field, which changes the statistics of bosons into semions.
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Masato Nakamura, Toshimichi Yasuda, Kazuo Kitahara, Mahito Kohmoto
1990 Volume 59 Issue 3 Pages
826-828
Published: March 15, 1990
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We calculated the spin depolarization of a quantum particle on a linear chain with Larmor frequencies arranged in a Fibonacci series and compared the result with those for alternating and random arrangements of Larmor frequencies. Though the effects of the thermal bath are not included in this calculation, our result implies that the spin depolarization of a quantum particle such as a muon is a useful probe for local magnetic properties of quasicrystals.
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Atsuko Ito, Eiko Torikai, Setsu Morimoto, Hiroko Aruga, Masae Kikuchi, ...
1990 Volume 59 Issue 3 Pages
829-832
Published: March 15, 1990
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The spin-glass Fe
0.5Mn
0.5TiO
3 (
TSG=21.5 K) has been studied by low-field dc-magnetization, neutron scattering and Mössbauer measurements. The results obtained by the magnetization and neutron scattering measurements indicate that only the longitudinal spin component freezes below
TSG. This fact shows that Fe
0.5Mn
0.5TiO
3 behaves as a typical Ising spin-glass in both of the measurements. However, the hyperfine fields
Hhf at Fe nuclei observed by the Mössbauer measurement point to directions other than the hexagonal
c-axis in the spin-glass state. This indicates that the transverse spin component contributes to
Hhf as does the longitudinal one. Combining the results obtained by the three methods, it is concluded that the transverse spin components fluctuate rather incoherently with one another with characteristic times longer than our Mössbauer time scale of ∼10
−7 s.
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Masaru Sugiyama
1990 Volume 59 Issue 3 Pages
833-842
Published: March 15, 1990
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A systematic approximation method for time evolutions of distribution functions of deterministic dynamical systems is developed when the distribution functions are not far from Gaussian. For simplicity and definiteness, the procedure of the method is shown by taking a simple dynamical system, that is, one-dimensional autonomous nonlinear oscillator. An essential point of the method is to replace an original initial value problem of the evolution of a distribution function by an appropriate initial value problem of the evolution of a Gaussian distribution function by using the Kullback-Leibler’s information. Basic properties of an initial value problem posed by the method are also studied.
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K. M. Tamizhmani, P. Punithavathi
1990 Volume 59 Issue 3 Pages
843-847
Published: March 15, 1990
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The infinite-dimensional Lie algebraic structure of a nonlinear higher-dimensional equation is studied and shown to contain a subalgebra of a loop algebra. It is shown that under some cases the equation can be transformed, by the first reduction, to the K-dV equation and the linear wave equation. The second reduction is done for the other cases.
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Miki Yamada
1990 Volume 59 Issue 3 Pages
848-856
Published: March 15, 1990
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The correlation length of the Heisenberg ferromagnetic chain with
S=1⁄2 at sufficiently low temperatures (
Remark: Graphics omitted.) is obtained numerically (
Remark: Graphics omitted.) by the thermal Bethe Ansatz method developed recently by Koma. The numerical result shows directly that the critical exponent ν of the correlation length ξ defined as ξ∼
T−ν is ν=1 and ξ is expanded in \sqrt
T near
T=0. These results coincide with the new spin wave theory in case of no spontaneous magnetization developed by Takahashi quantitatively with the accuracy of 2×10
−3% and 7×10
−2% as for the first and second order terms of a low-temperature expansion respectively.
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Takahiro Yamaguchi, Yoshitaka Yamamoto, Kuninosuke Imaeda
1990 Volume 59 Issue 3 Pages
857-867
Published: March 15, 1990
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We investigate the response of the Oregonator by adding an external periodic force
Aη cos (ω
ητ) to the second component. The order of appearance of a π(
m) band in the mode diagram obtained by changing both the amplitude and frequency of the external force, becomes complex. But we found that the order of appearance of an extension
Π*(
m) band of π(
m) band is regular. We also, investigated the order of appearance of band for
Aη=−10 and π(
m,
m+1,
m+2) band for
Aη=−11 by using a piecewise linear map approximating the strange attractor in the region of ω
η from 4.8 to 6.0. We find that the result of the piecewise linear map concerning the order of appearance of bands, in limited regions of the control parameters
Aη and ω
η agrees qualitatively with that of the forced Oregonator. Furthermore, we investigated the relation between the multiplicity
M and ω
η for bands which appear in the region from 4.4 to 7.2 (
Aη=−10).
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Yoshitaka Yamamoto, Kuninosuke Imaeda
1990 Volume 59 Issue 3 Pages
868-876
Published: March 15, 1990
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The response of the Oregonator exerted a periodic force with a changing frequency and a constant amplitude is studied. We observed a hysteresis phenomenon as in a previous paper when the amplitude is changed with time. We found a new phenomenon which is a transient phenomenon and is induced by the time variation of the frequency of the external periodic force. But we found that the relaxation phenomena observed in the previous case were absent in the present case. The same transient phenomenon is observed when the forced Oregonator is acted on by a pulse of a second external periodic force.
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Makoto Katori, Norio Konno
1990 Volume 59 Issue 3 Pages
877-887
Published: March 15, 1990
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A new formulation is presented to obtain lower bounds for the critical value λ
c of the contact processes. A series of correlation inequalities are derived and combined with a set of correlation identities to estimate an order parameter ρ
λ. A simplified derivation of the Dobrushin and the Harris bound is presented following our formulation. The Griffeath bound is extended to the general dimensions
d≥1. For the one-dimensional system, improved bounds are calculated. These bounds are classified systematically according to the choice of a basic cluster.
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Tsuyoshi Horiguchi, Tohru Morita
1990 Volume 59 Issue 3 Pages
888-892
Published: March 15, 1990
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An antiferromagnetic classical
XY model with the nearest-neighbor interaction 2
J and the next-nearest-neighbor interaction δ
J on a one-dimensional lattice is investigated in the low temperature limit. We obtain the asymptotic behaviors at long distances, of the two-spin correlation function for δ>1⁄2 and of the chirality-chirality correlation function for δ=1. The behavior of the latter correlation function is shown to be similar to the one of the two-spin correlation function for the Ising model with the nearest-neighbor interaction
J/2 on a one-dimensional lattice.
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Teiichiro Ogawa, Masaharu Taniguchi, Keiji Nakashima, Hirofumi Kawazum ...
1990 Volume 59 Issue 3 Pages
893-897
Published: March 15, 1990
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Dissociation of CH
4 and H
2O induced in collisions with electrons was investigated by measuring decay curves of the intensity of the Balmer emission of the excited hydrogen atom H
*(
n=4). The azimuthal quantum number (
s,
p,
d) distributions of H
*(
n=4) were obtained by a time-resolved single-photon counting method. The distribution (%) for methane is H
*(4
s):H
*(4
p):H
*(4
d)=42±4:4±11:51±11 at the electron energy of 25–300 eV, and that for water is H
*(4
s):H
*(4
p):H
*(4
d)=27±5:15±11:55±11 at 23–300 eV. The emission cross sections of each sublevel were obtained at 35, 50, 100 and 300 eV.
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Atsushi Fukuroda, Nobuo Kobayashi, Yozaburo Kaneko
1990 Volume 59 Issue 3 Pages
898-901
Published: March 15, 1990
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With a high resolution ion energy-loss spectrometer, fine structure transition cross sections for the collision systems of Ar
+ and Ne
+-rare gases have been measured in the incident ion energy range from 100 to 2000 eV. It appears that for each ion, the magnitude of the cross sections can be put in order with the absolute values of the ionization energy differences between the projectiles and targets; |
ΔE|. If σ
0 is the fine structure transition cross section of the symmetric system, that of an asymmetric system becomes σ
0 exp (−|
ΔE|⁄α).
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Atsushi Matsumoto, Atsunori Danjo, Shunsuke Ohtani, Hirosi Suzuki, Hir ...
1990 Volume 59 Issue 3 Pages
902-917
Published: March 15, 1990
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The technique of crossed electron-ion beams has been employed to measure the absolute cross sections for single ionization of Ne
2+, Ar
2+, Kr
2+ and Xe
2+ ions at electron energies ranging from below threshold to 1000 eV. Detailed descriptions of the experimental apparatus and procedures to determine the absolute cross sections are presented, and are discussed check points for reliability and consistency as well as possible contributions of metastable contents in the ion beam. The total systematic error in the cross sections is estimated to be within ±9%. A distinct discrepancy is observed for Ne
2+ between the measured cross section curve and results of semiempirical calculation using the Lotz formula. The cross sections for Ar
2+, Kr
2+ and Xe
2+ reveal significant contributions from excitation-autoionization processes in addition to direct ionization, especially in the near threshold energy regions.
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Yasuhide Fukumoto
1990 Volume 59 Issue 3 Pages
918-926
Published: March 15, 1990
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An exact solution of the Navier-Stokes equations is established for a general initial/boundary-value problem which describes the development of an incompressible circulatory flow outside an infinite circular cylinder with uniform suction or injection. An asymptotic evaluation of the solution, valid after a long time, reveals the effects of suction or injection upon the ultimate flow behavior; for
R>2, the circulation at infinity remains unchanged throughout the process if it is finite initially; for
R≤1, all of the vorticity, even if its amount is infinite, is blown away to infinity and the flow becomes irrotational in the final state; intermediate between them is the case of 1<
R≤2. Here
R=
Va⁄ν, with
V,
a and ν being the suction velocity, radius of the cylinder and the kinematic viscosity, respectively.
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Takahisa Ozeki, Masafumi Azumi
1990 Volume 59 Issue 3 Pages
927-933
Published: March 15, 1990
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Access to the second stability regime of the ballooning modes is realized near the plasma surface in a nearly circular tokamak. It is shown that the plasma with a high safety factor and low shear near the plasma surface can access to the second regime without the effect of X-point, even if the safety factor at the magnetic axis is low (\lesssim1). The scaling of the second stability boundary as a function of the safety factor, the shear, aspect ratio, elongation and triangularity has been numerically calculated by using the pressure profile optimization technique. Results show that the accessibility to the second stability regime is high in a low aspect ratio and a positive triangularity (δ>0) regime. By the effect of a pedestal current profile, the global shear near the plasma surface is reduced, and the accessibility is improved.
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Reiji Sugaya
1990 Volume 59 Issue 3 Pages
934-938
Published: March 15, 1990
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The velocity space diffusion equation which describes a distortion of the velocity distribution function due to nonlinear Landau damping of electrostatic waves in a plasma without magnetic field is derived from the Vlasov-Maxwell equations by perturbation theory. The conservation laws for total energy and momentum densities of waves and particles are verified, and the time evolutions for energy and momentum densities of particles are given by means of nonlinear wave-particle coupling coefficient in kinetic wave equation. The obtained equations can be also available for analysis of energy transfer between waves and particles caused by nonlinear Landau damping due to non-magnetized particles in a magnetized plasma.
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Yushi Kato, Norio Satomi, Masahiro Nishikawa, Kenji Watanabe
1990 Volume 59 Issue 3 Pages
939-953
Published: March 15, 1990
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In CTCC spheromak experiment, a coaxial gun produces initial plasma and ejects it into a confinement region surrounded by metal wall where magnetic flux is conserved, i.e. Flux Conserver (FC). A time of production is only about 0.1 ms and a extinction time of the plasma is about 1.5 ms. There is no supply of energy to spheromak during this duration, and there is scarcely any occurrence of ruinously global instabilities, except for a intermittent instability (stepwise instability). Then spheromak is gradually decaying due to its own resistivity. The present plasma have been studied experimentally from view point of impurity behavior and the physical process about the temporal behavior of the spheromak have been also clarified by the use of zero dimensional energy balance model.
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Akira Hamada, Seishi Yamamoto, Yasuhiro Shinnaka
1990 Volume 59 Issue 3 Pages
954-958
Published: March 15, 1990
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The crystal structures of NH
4SCN are determined in the tetragonal phase I (122°C) and the orthorhombic phase II (100°C, 110°C and 115°C) from X-ray diffraction data. In phase I, SCN
− ion is in disordered state taking two equivalent configurations. In phase II, the ordering of SCN
− ion correlates to the spontaneous displacement of NH
4+ ion. X-ray critical diffuse scattering is observed at the
Z-point of the Brillouin-zone boundary in phase I and critical temperature is determined to be 117°C. The I–II phase transition is explained by a coupling system between the orientational disorder and the phonon.
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Teruyuki Tamaki, Nobuyoshi Wakabayashi
1990 Volume 59 Issue 3 Pages
959-964
Published: March 15, 1990
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The X-ray diffuse scattering intensity was measured for a highly oriented pyrolytic graphite (HOPG) sample as well as for a single crystal kish graphite sample. The measurements were carried out both at 10 K and at room temperature. The HOPG sample gives rise to a temperature independent diffuse scattering along the
c*-direction. This scattering was analyzed as that due to the crystallite boundaries. The thermal diffuse scattering exhibits unusual features which could be interpreted to be a result of the coupling of low frequency phonons with an excitation mode which is yet to be identified.
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Hideki Seto, Yukio Noda, Yasusada Yamada
1990 Volume 59 Issue 3 Pages
965-977
Published: March 15, 1990
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Precise X-ray diffraction study has been carried out in the vicinity of fcc-fct transition in Fe–Pd alloys in order to investigate the pretransitional phenomena at martensite transformations. Using a high-resolution X-ray spectrometer with fine temperature control unit, the temperature variation of the profiles of Bragg reflections were measured. A new intermediate phase was discovered in a narrow temperature range between the austenite (fcc) and the martensite (fct) phase. Its structure is characterized by a “two-tetragonal-mixed” phase, and interpreted as a coherent mixture of two tetragonal lattices with different tetragonalities. The origin of the stability of this intermediate phase has been investigated. It may be interpreted in terms of the previously postulated “crest-riding-periodon” phase.
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Hideki Seto, Yukio Noda, Yasusada Yamada
1990 Volume 59 Issue 3 Pages
978-986
Published: March 15, 1990
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Neutron and X-ray scattering studies were carried out in the temperature region above the “two-tetragonal-mixed” phase discussed in part I of this series of paper. Quasi-elastic scattering were observed to increase as the temperature was decreased toward the transition point from fcc to the intermediate phase. The results were interpreted as due to random distribution of micro-regions of the low temperature structure (embryonic fluctuations) whose density increasing with decreasing temperature. Together with the results discussed in part I, the process of the first order phase transition in Fe–Pd was inferred by dividing the temperature region into the four regimes as follows; cubic phase (regime (I))→random distribution of tetragonal ernbryos (regime (II))→two-tetragonal-mixed phase (regime (III))→tetragonal phase with variants separated by sharp domain boundaries (regime (IV)).
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Tomio Iwasaki
1990 Volume 59 Issue 3 Pages
987-992
Published: March 15, 1990
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The mean-field properties for the low- and high-field phase of the bcc solid
3He are calculated including the two-, three-, four-, six-particle exchange processes. Using these exchange processes, we develop the spin wave theory for the U
2D
2 phase. We investigate the effects of the six-particle exchange process. The specific heat strongly depends on the six-particle exchange process at temperatures near
T=0.
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Kiyomi Okamoto, Kaoru Yasumura
1990 Volume 59 Issue 3 Pages
993-1001
Published: March 15, 1990
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We investigate the ground state of the alternating spin-1/2
XY chain with the anisotropy
(
Remark: Graphics omitted.),
where 0≤γ≤1 and 0≤δ≤1. From the exact results of the ground state energy calculation, the ground state is found to be either one of the following three states: the spin fluid state (γ=δ=0), the effective singlet pair state (ES state; δ>γ) and the Néel state (γ>δ). We also exactly calculate the asymptotic form of the longitudinal spin correlation 〈
SizSjz〉 in the long distance limit. Both its functional form and the parameter dependence of the correlation length are quite consistent with our picture for the ES state and the Néel state.
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Atsushi Ikawa, Hideo Fukutome
1990 Volume 59 Issue 3 Pages
1002-1016
Published: March 15, 1990
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Electronic and lattice structures of terminal and internal defects in a Se chain are systematically studied with the semi-empirical model developed previously. Structures of the defects are as follows: negative ion
1C
1−, a little altered helix; neutral radical
2C
10, and positive singlet ion
1C
1+, planer structures with four atoms; positive triplet ion
3C
1+, an acute triangle; n-type polaron
2P
−, locally relaxed helix; p-type polaron
2P
+ and self-trapped triplet exciton
3Ex, planer zig-zag structures with five atoms; intimate valence alternation pair (IVAP), a ramification of a Se atom. The IVAP is of C
3+−C
1− type. Interactions of a Se chain with Li, H and O are studied as a model of the effects of the wall on a Se chain enclosed in a mordenite channel (M–Se). A Se chain makes unusual charge transfer complexes with Li. Hydrogen binds to an internal Se making it C
3+ type or blocks a terminal Se. Based on these calculations we propose a model for photo-induced events in M–Se.
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Ichiro Terasaki, Shin-ichi Uchida, Setsuko Tajima, Kunimitsu Uchinokur ...
1990 Volume 59 Issue 3 Pages
1017-1024
Published: March 15, 1990
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Thin films of LaB
6 were prepared on sapphire, Si and GaAs by electron-beam deposition. Superconductivity was not observed above 1.6 K, and the anomalous magnetoresistance, associated with the weak localization effects, indicated that the spin-orbit scattering rather than the magnetic impurity scattering is strong in this film. From the detailed analysis of the magnetoresistance, we estimated the superconducting transition temperature of our sample is, if it exists, less than 40 mK. It turned out that the parallel magnetoresistance is larger in magnitude than the perpendicular one. This large parallel magnetoresistance is beyond the localization theory, and has never been observed in other materials.
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Hiroshi Ueyama
1990 Volume 59 Issue 3 Pages
1025-1028
Published: March 15, 1990
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An application of the method of quantum Langevin equation to a many-body system far from equilibrium is considered. A coupled set of Langevin equations is derived exactly. By approximate reductions of variables, the generalized Langevin equation of the center of mass of electrons in solid is derived, that has previously been derived on heuristic grounds.
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Takashi Nakayama
1990 Volume 59 Issue 3 Pages
1029-1038
Published: March 15, 1990
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The crystal structures and the band structures of ultrathin layered ZnSe/ZnS superlattices are calculated by the Valence Force Field model and the self-consistent pseudopotential method. The resulting crystal structures show that the macroscopic elastic theory simulates strained structures of the present superlattices well. It is shown that some energy levels oscillate due to the symmetry with changing the layer thickness while strain causes another level splitting. The possibility that the ZnSe/ZnS superlattice on the GaAs substrate becomes the strain-induced light-hole gap material with decreasing the layer thickness is suggested. The structural stability and the band offset are also discussed.
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Bunjyu Shinozaki, Takasi Kawaguti, Yasunobu Fujimori
1990 Volume 59 Issue 3 Pages
1039-1046
Published: March 15, 1990
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The relation between the pair breaking parameter δ and the inelastic scattering rate 1⁄τ
in has been studied for Al(sheet resistance (
Remark: Graphics omitted.)), Sn(<70 Ω) and Pb(<3 Ω) films. The δ
IIIF agrees well with δ
M independent of materials and dirtiness: The δ
IIIF is determined by the analysis of the excess conductance with adding the correction term to the Maki-Thompson term and δ
M is obtained from the relation δ=πh⁄8
kBTτ
in, where the τ
in is determined by the analysis of the magnetoconductance. The (
Remark: Graphics omitted.) dependence of δ
fluc,e-eM for Al and also Sn films, where the electron-phonon inelastic scattering contribution is subtracted experimentally, is in quantitative agreement with theories independent of materials. This implies that the material dependence of coefficients δ
0 and
a in the experimental expression (
Remark: Graphics omitted.) is caused by e-p in-elastic scattering depending on materials and dirtiness of films.
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Masaru Kato, Kazushige Machida, Hiizu Nakanishi, Mitsutaka Fujita
1990 Volume 59 Issue 3 Pages
1047-1058
Published: March 15, 1990
Released on J-STAGE: June 01, 2007
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Spatially modulated magnetic phases are investigated within the mean field theory for an itinerant electron model, i.e. the Hubbard model on a two-dimensional square lattice. By numerically diagonalizing the Hamiltonian for finite-size systems under a periodic boundary condition, we examine relative stability and physical properties of several possible magnetic states. When the electron fillings are nearly half-full, the diagonally or vertically modulated spin density wave (SDW) state is stabilized over the uniform antiferromagnetic state and a crossover from the vertical to the diagonal states appears. The diagonal or vertical stripe state is characterized by the presence of the midgap band due to the soliton lattice formation inside the main SDW gap, being an insulator. The wave length λ
SDW is linearly proportional to the excess carrier concentration. Excess carriers are accommodated in the form of the soliton lattice, forming a charge density wave whose wave length is λ
SDW⁄2.
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Shuichiro Anzai, Hiroshi Sakamoto, Kazuo Hatakeyama, Satoru Ohta, Sato ...
1990 Volume 59 Issue 3 Pages
1059-1070
Published: March 15, 1990
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Magnetization σ, susceptibility χ and electrical resistivity ρ are investigated on (Cr
1−xTi
x)
5S
6 (
x≤0.60). As
x increases,
Tt (the transition temperature between the helico-canted antiferromagnetic and the collinear ferrimagnetic states) decreases more steeply than as the Curie temperature
Tc. The ferrimagnetic magnetization decreases up to a compensation concentration at
x\simeq0.30. It increases as
x further increases; a revived ferrimagnetic state (RFS) appears. The Curie temperature
Tf for RFS decreases with
x. Immediately below RFS, a reentrant spin-glass like state is found over the very wide range of
x, which shows an anomaly in ρ. This state exhibits a spontaneous magnetization in a narrow range of
x. One discusses these features on the view point of the mean field and the local atomic situations, by using the exchange parameters evaluated from the paramagnetic χ through the Néel law.
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Hiroyuki Deguchi, Keita Takahashi, Hidenori Kubo, Kazuyoshi Takeda
1990 Volume 59 Issue 3 Pages
1071-1078
Published: March 15, 1990
Released on J-STAGE: May 29, 2007
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Magnetic and thermal properties of Co
1−xMn
xCl
2·2H
2O with competing exchange interactions have been studied experimentally, For the system with
x∼0.5, the magnetic heat capacity have revealed only a broad maximum around 5 K, which is quite different from the heat capacity peak of λ-type for the pure systems and similar to that observed in metallic spin-glasses. The hysteresis in the magnetic susceptibility and thermoremanent magnetization have been observed in the mixtures with
x≤0.5, reflecting the frustration of magnetic interactions, while normal antiferromagnetic behavior has been seen in the region
x>0.5. The magnetic phase diagram of this system is given, which contains four states: paramagnetic, antiferromagnetic, frustrated antiferromagnetic and anisotropic spin-glass states.
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Hideaki Sakata, Katsumi Hamano, Xiaoqing Pan, H.-G. Unruh
1990 Volume 59 Issue 3 Pages
1079-1092
Published: March 15, 1990
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The processes of nucleation and annihilation of discommensurations (DC’s) in the first-order C-IC transition in K
2ZnCl
4 have been studied by the measurement of the time evolution of the dielectric constant during the transition and by the observation of domain structure by etching, powder, replica and TEM techniques. In the C-to-IC transition, stripples are first nucleated at crystal defects and clusters of DC’s expand from them one-dimensionally in the
c-direction. The growth of the clusters results from the nucleation and growth of stripples along the boundaries of the clusters. The IC-to-C transition proceeds through the formation and growth of antistripples. Several stages of the domain pattern coarsening process have been revealed. A very complicated domain pattern with vortices is finally realized.
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Kunitsugu Soda
1990 Volume 59 Issue 3 Pages
1093-1103
Published: March 15, 1990
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Hydration structure of nonpolar spherical solutes with various radii has been analyzed using an integral equation method. Radial distribution functions of solvent water molecules have been evaluated assuming a wide range of values for the radii of O and H atoms. Strikingly different from hard-sphere solvents and the single-site model water, the three-site model water has radial distribution functions of O and H atoms strongly dependent on solute size, and each of their contact densities changes oscillatively with increase in solute size. Repulsive interactions of not only O atoms but also H atoms with solute are essential to the formation of such solvation structure. From these results, a physical mechanism for the hydration structure formation is proposed as some network structure due to the H-bonding capability of water is supported by the cooperation of repulsive forces between solute and each of O and H atoms.
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Yasuyo Hatano, Toshiaki Kakitani, Akira Yoshimori, Minoru Saito, Nobor ...
1990 Volume 59 Issue 3 Pages
1104-1116
Published: March 15, 1990
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By using a spherical hard core model, Monte Carlo simulation study has been made on physico-chemical properties of the dielectric saturation taking place in polar solvents surrounding a charged molecule. The strength of the dielectric saturation has been evaluated by the magnitude of the free energy curvature as a function of the polarization in the radial direction. Detailed analysis is made on the problem how the dielectric saturation shell-width and its strength change, depending on the valency (magnitude of the charge) of the solute molecule and on the dipole moment of the solvent molecule as well as on the radii of solute and solvent molecules. Based on these results, we conclude that the dielectric saturation is a considerably universal phenomenon which occurs in various molecular systems.
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Kazuo Gesi
1990 Volume 59 Issue 3 Pages
1117-1118
Published: March 15, 1990
Released on J-STAGE: May 29, 2007
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