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Miki Wadati
1990 Volume 59 Issue 12 Pages
4201-4203
Published: December 15, 1990
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A nonlinear partial differential equation which describes wave propagations in random media is presented. Under the assumption of Gaussian white randomness, it is shown that the amplitude of a soliton decreases asymptotically as
x−1⁄2,
x being the distance of the propagation.
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Kazuhiro Satoh
1990 Volume 59 Issue 12 Pages
4204-4207
Published: December 15, 1990
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The behavior of a cellular automaton model for an ecosystem (K. Satoh: J. Phys. Soc. Jpn.
58 (1989) 3842) is reinvestigated on the hexagonal lattice. It is found that a variety of single and multiarmed spiral patterns are self-organized.
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Hideki Iimura, Yoshinori Nakahara, Shin-ichi Ichikawa, Kazuhiro Kotani ...
1990 Volume 59 Issue 12 Pages
4208-4210
Published: December 15, 1990
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The hyperfine structure of the transitions 4
f3(
4Io)5
d 5G2o-4
f3(
4Io)6
p 5H3 (λ=601.94 nm) and 4
f3(
4Io)5
d 5G3o-4
f3(
4Io)6
p 5H3 (λ=604.83 nm) of PrII has been measured by collinear laser-ion-beam spectroscopy. The magnetic-dipole constant
A and the electric-quadrupole constant
B of the levels involved have been determined to be:
(
Remark: Graphics omitted.)
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Daijiro Yoshioka, Allan H. MacDonald
1990 Volume 59 Issue 12 Pages
4211-4214
Published: December 15, 1990
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Two-dimensional electron-hole systems with long excitonic life-times can be realized in double quantum well systems by applying an electric field which localizes electrons and holes in opposite wells. The ground state of such a system is investigated theoretically and numerically in the strong magnetic field limit. It is shown that when the separation between the electron layer and the hole layer,
d, is small, an excitonic condensate state is realized. On the other hand, when
d is large, either independent fractional quantum Hall states for electrons and holes or coupled Wigner crystal (dipole density wave) states may be realized depending on the filling factor. The difference in photoluminescence spectra between these states is discussed.
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Haruhisa Toyoda, Akihiko Sumiyama, Yasukage Oda, Kunisuke Asayama
1990 Volume 59 Issue 12 Pages
4215-4218
Published: December 15, 1990
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The Meissner effect in Cu doped with Fe, Co and Ni, which is induced by the proximity effect of Nb, is first measured down to 40 mK. It is found that the thickness ρ of the Meissner region in Cu increases in proportion to
T−1⁄2, similarly to the normal impurity case. The thickness ρ is determined mainly by the electronic mean free path in Cu and the interface between Cu and Nb. The
T−1⁄2 dependence of ρ suggests that the pair breaking effect due to magnetic impurities weakens linearly with decreasing temperature below 1 K.
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Shun-ichi Kobayashi, Akihiko Nakamura, Fumio Komori
1990 Volume 59 Issue 12 Pages
4219-4222
Published: December 15, 1990
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The temperature and magnetic field dependence of sheet resistance was measured in aluminum granular films which consisted of 10 A grains and thin oxides on grain surfaces. For the samples with normal resistance less than 6 kohm, a superconducting transition was observed, while the others behaved as insulators. The transition between superconductor and insulator was induced also by a magnetic field, and the normal sheet resistance at the boundary was 6.7 kohm. The results are discussed in connection with the theories for the universal critical resistance
RQ (=h/4e
2), and with the results of previous experiments for films of larger grains.
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Kazushige Machida, Masahiro Nakano
1990 Volume 59 Issue 12 Pages
4223-4226
Published: December 15, 1990
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To explain recursive cascades of the field-induced spin density wave phase in organic conductors discovered recently, a standard model or two-dimensional anisotropic Hubbard model under a perpendicular field is investigateed: the SDW ground state is found to be characterized by a set of countable many-order parameters (OP) of the Fourier components of the SDW modulation or by a distribution of these OP’s. Due to interference between the lattice commensurability and magnetic length, the OP distribution differs for every rational field, resulting in a phase diagram with devil’s staircase like infinite cascades.
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Tôru Sakai, Minoru Takahashi
1990 Volume 59 Issue 12 Pages
4227-4230
Published: December 15, 1990
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A 1D
S=1 Heisenberg antiferromagnet in a magnetic field
H(⁄⁄
z-axis) at
T=0 is studied by numerical diagonalizations. It is found that a phase transition exists at
Hc1(=
Δ), where
Δ is the Haldane gap, and the transverse staggered susceptibility χ
stxx diverges and the spin correlation is asymptotically 〈
S0xSrx〉∼(−1)
rr−η between
Hc1 and
Hc2(=4). If the system is quasi-1D, even small interchain interactions can make canting Néel order within a mean field approximation for interchain interactions. This is consistent with a recent NMR measurement for NENP at low temperature.
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Seitaro Mitsudo, Michinobu Mino, Hitoshi Yamazaki
1990 Volume 59 Issue 12 Pages
4231-4234
Published: December 15, 1990
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Transverse pumping at the first-order Suhl instability in YIG has been performed at a pumping frequency of 3.3 GHz at 4.2 K. Above the spin-wave instability threshold, period-doubling cascades and chaotic auto-oscillations are observed. From time-series data, return maps, fractal dimensions, phase space portraits of strange attractors, two-dimensional Poincaré sections, and singularity spectrum
f(α) are obtained. The Poincaré sections of the phase space trajectories exhibit the stretching and folding which are characteristics of strange attractors. At the onset of chaos, the
f(α) spectrum is consistent with the universal one.
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T\={o}ru Ozaki, Tomosuke Yoshida, Eiji Nakamura
1990 Volume 59 Issue 12 Pages
4235-4238
Published: December 15, 1990
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Birefringence for light travelling along the
c axis was observed above the Curie temperature
Tc in the strained regions characteristic of the KH
2PO
4 crystal. The birefringence and the area of the birefringent regions increase as the temperature approaches
Tc. In the strained regions, the crystal is optically biaxial and negative, and the optical indicatrix has the same orientation as that in the ferroelectric phase. It is found that the birefringence is induced by the strain of
x6 type around the lattice imperfections through a photoelastic effect.
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Makoto Iwata, Yoshihiro Ishibashi
1990 Volume 59 Issue 12 Pages
4239-4242
Published: December 15, 1990
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The temperature dependences of dielectric dispersion in (CH
3NH
3)
5Bi
2Cl
11 and (CH
3NH
3)
5Bi
2Br
11 single crystals, which undergo the para-ferroelectric phase transition (I→II) at 307 K and 311.5 K, respectively, were measured near the phase transition point in the frequency range from 1 MHz to 1 GHz. The dielectric dispersion exhibited was found to be of the Debye-type. The critical slowing down was observed near the phase transition point.
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Kazuhiro Kiso
1990 Volume 59 Issue 12 Pages
4243-4244
Published: December 15, 1990
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A relation between certain evolution equations defined by Lax equations is shown. This gives a transformation from the solution space of the Dym hierarchy to the solution space of the modified KdV hierarchy and also gives transformations between the solution spaces of related equations.
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Yuji Nakawaki
1990 Volume 59 Issue 12 Pages
4245-4259
Published: December 15, 1990
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We give an infinite volume formulation of quantum inverse scattering method for Heisenberg
XXZ model, by making use of Jost solutions of difference equations satisfying prescribed asymptotic boundary conditions. We find operator identities among the Jost solutions which enable us to obtain Gel’fand-Levitan equations more easily than any previous formulations. By solving an integral equation, we express scattering data operators in terms of solely reflection coefficient operators, which are creation and annihilation operators of magnons and their bound states. We also see that when expressed in terms of them, Hamiltonian and other integrals of motion are diagonalized in free bosonic forms so that magnon and their bound states constitute a complete set of bases of Fock space.
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Masao Nomura
1990 Volume 59 Issue 12 Pages
4260-4271
Published: December 15, 1990
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Quantum
d-functions
dmkj, which constitute the (2
j+1)-dimensional representation matrix of the quantum group
U[
slq(2)], are investigated to specify them as wave functions of ‘quantum symmetric tops’ in the noncommutative space. It is shown that the
d-functions are solutions to the equation
RTj′ Tj″=
Tj″ Tj′ R, known in the quantum inverse scattering method, where
R is the (2
j′+1)×(2
j″+1) braiding matrix of
U[
slq(2)]. Quantum
d-functions fulfill also Zamolodchikov-Zamolodchikov equation, which affords a new kind of braiding matrix that expresses scattering of a couple of quantum symmetric tops. Explicit forms of quantum
d-functions and several symmetry relations are obtained for them. Differential operations are given which describe space- and body-referred angular momentum operators of the quantum symmetric top. Description of quantum
d-functions in terms of creation and annihilation operators is also discussed.
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Akira Nakamura
1990 Volume 59 Issue 12 Pages
4272-4278
Published: December 15, 1990
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We have obtained the explicit one-soliton solutions of the 1+1 dimensional Toda molecule equation, (∂⁄∂
t)
2log
V(
n,
t)−
V(
n+1,
t)+2
V(
n,
t)−
V(
n−1,
t)=0, consisting of arbitrary number of particles which satisfy the molecule boundary condition
V(
n,
t)=0 at
n=−
M′ and
M″ (
M′,
M″≡arbitrary positive integer constants). It has been shown that for the properly chosen values of arbitrary constant parameters and the large molecule limit, the present Toda molecule one-soliton solutions actually reproduce the well known infinite Toda lattice one-soliton solutions.
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Morikazu Toda, Yoshiko Okada, Shinsuke Watanabe
1990 Volume 59 Issue 12 Pages
4279-4285
Published: December 15, 1990
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We derive an exact dual lattice of a nonlinear version by introducing a double exponential lattice, where not only the interaction potential but also the momentum are of the exponential type. This is the first example of the system with duality in nonlinear systems. The double exponential lattice can be extended to multi-component systems where the parameters characterizing the potential and the momentum are not uniform. In a small-amplitude limit, the double exponential lattice is reduced to the usual exponential lattice. It is shown that the exponential lattice composed of different mass particles is dual to that composed of the interaction with different parameter
b in such a limit.
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Kiyomi Okamoto
1990 Volume 59 Issue 12 Pages
4286-4296
Published: December 15, 1990
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The alternating
S=1⁄2
XY chain in the Lorentzian random field in the
z-direction is investigated by the use of the pseudo-Fermion representation. The random-averaged one-particle Green’s functions for the pseudo-Fermions are exactly calculated, which enables us to exactly construct the thermodymanics of this model. The spin correlation function 〈
SizSjz〉 is also studied at
T=0. The dimerized state (which is the ground state in the absence of the random field) is completely destroyed by any small (but finite) amount of the random field.
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Kazuhiro Satoh
1990 Volume 59 Issue 12 Pages
4297-4301
Published: December 15, 1990
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A random neural network model is found to exhibit rhythmic activity which is very similar to that of the brain waves. Dimensional analysis suggests that chaotic attractors reconstructed by the embedding method are high-dimensional ones.
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A. Boushehri, A. Maghari
1990 Volume 59 Issue 12 Pages
4302-4305
Published: December 15, 1990
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Direct inversion method is used to obtain the xenon interaction potential from the extended principle of corresponding states. We have employed the experimentally reduced viscosity collision integrals obtained from the corresponding-states correlation, and performed an INVERT to determine the reduced potential energy curve corresponding to this collision integral. Comparison of this with the potential independently known from molecular-beam scattering shows a good agreement with the Lee potential.
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Rajesh Srivastava
1990 Volume 59 Issue 12 Pages
4306-4312
Published: December 15, 1990
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Distorted wave approximation results for the differential cross section and various angular correlation parameters concerning electron impact excitation of the 3
1P state of magnesium from the ground 3
1S state are presented and compared with recent experimental data and other theoretical calculations. The comparison of the present calculations with the experiment suggests the suitability of the distorted wave approximation to describe the 3
1S-3
1P transition in magnesium at 40 eV.
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Masahiro Nakagawa
1990 Volume 59 Issue 12 Pages
4313-4322
Published: December 15, 1990
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A complete expression of the elastic free energy of biaxial cholesterics is derived in terms of quadratic combinations of a spatial gradient of the biaxial tensor order parameter. As a result of the tensorial description of an isotropic scalar quantity, the elastic free energy is found to consist of 12 bulk elastic constants, 3 chiral terms, and 3 surface terms under
D2 symmetry in the Schoenflies notation and expressed in terms of the microscopic order parameters characterising the biaxial molecular ordering as well as the uniaxial one.
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Shigeo Kida, Youichi Murakami, Koji Ohkitani, Michio Yamada
1990 Volume 59 Issue 12 Pages
4323-4330
Published: December 15, 1990
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Statistical properties of a forced Navier-Stokes turbulence are studied numerically using a high-symmetric flow. A spectral simulation with resolution of 340
3 realizes the
k−5⁄3 power law with Kolmogorov constant of 1.8 in the one-dimensional longitudinal and lateral spectra over one decade of wavenumber. The time-averaged micro-scale Reynolds number is 180. The normalized form of energy spectrum is the same as that for a previously reported freely-decaying turbulence (Kida and Murakami, Phys. Fluids
30 (1987) 2030) in both the inertial and dissipation ranges. The flatness factor of an individual Fourier component of velocity increases monotonically with wavenumber in the inertial range and saturates at about 3.7 in the dissipation range. The flatness factor of vorticity, on the other hand, is about 9. Such a big difference in the magnitude of flatness factor for a physical field quantity and its Fourier component is discussed with regard to the non-local interaction of Fourier components.
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Kenichi Nanbu
1990 Volume 59 Issue 12 Pages
4331-4333
Published: December 15, 1990
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The variable hard-sphere model of Bird, which is used in simulating molecular collisions in pure gas, is extended so that it is applicable to the collisions in gas mixture. The constant in the model is determined from the coefficient of diffusion.
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R. A. Clemente
1990 Volume 59 Issue 12 Pages
4334-4337
Published: December 15, 1990
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Using a model based on simple resistive MHD equations, where thermal conductivity, radiation losses and inertial effects are neglected, it is shown that for systems with
j·
B=0 and
j along an ignorable coordinate, plasma evolution can be described through the evolution of some proper parameter. This is possible thanks to the fact that an initial uniform temperature profile remains uniform during diffusion. A subtle balance between plasma flow and ohmic dissipation is responsible for the temperature uniformity. An example of application, for the special case of an elliptical plasma column in an external quadrupole magnetic field, is shown.
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Takahisa Ozeki, Masafumi Azumi
1990 Volume 59 Issue 12 Pages
4338-4345
Published: December 15, 1990
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The stability of the
n=1 internal kink mode in a tokamak is numerically analyzed for plasmas with a centrally peaked pressure profile. The effect of pressure profile is studied by the comparison of a strongly peaked pressure inside the
q=1 surface with a parabolic pressure profile. The effects of shaping, i.e., elongation and triangularity, are also studied for the both pressure profiles. The plasma with the strongly peaked pressure profile has higher limiting value of poloidal beta defined within the
q=1 surface than that of the parabolic pressure profile. Though the beta limit reduces with the increase of the elongation, the plasma with the peaked pressure profile has larger improvement due to the triangularity than that with the parabolic pressure profile. However, to enter the second stability region of the
n=1 internal kink mode, the plasma with a flat pressure profile and the large minor radius of the
q=1 surface is effective.
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Sizuka Kurioka, Kazuyosi Ikeda
1990 Volume 59 Issue 12 Pages
4346-4361
Published: December 15, 1990
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The detailed behaviour of isotherms is investigated for the one-dimensional gas model proposed and discussed by Ikeda in paper I; the model consists of molecules with hard cores, short-range (square-potential) repulsions and infinitely-long-range attractions (given by the potential −2
a⁄
L,
a=positive constant,
L=length of the gas). On the basis of
R (region of negative pressure coefficient), the intersection and inversion of isotherms in the
P′-
l′ plane (
P′=reduced pressure,
l′=reduced specific volume) are studied, in connection with the phase transitions. The interaction constants σ′ and
a′ are so chosen as to represent the features of water. Correspondence between diagrams in the
T′-
l′,
P′-
T′ and
P′-
l′ planes (
T′=reduced temperature), including
R and
R′ (region of negative thermal expansivity), is discussed. The behaviour of isotherms in the liquid phase for this model explains the anomalies of liquid water.
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Yoshiko H. Ohashi, Tomokazu Umezawa, Mitsuru Fukuchi, Kazutoshi Ohashi ...
1990 Volume 59 Issue 12 Pages
4362-4365
Published: December 15, 1990
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Thermal diffusivities of sputtered SiC thin films were measured by using ac-calorimetric method. X-ray diffractions showed that the as-sputtered samples were in amorphous state and the thermal diffusivity of the SiC thin film was 0.40 cm
2/s. After heat-treatment at 400°C for 5 hours in argon gas, there occured recrystallization and then the thermal diffusivity increased to be 0.62 cm
2/s. Furthermore, the effect of SiO
2 impurity on thermal diffusivity was investigated. The impurity acting as a source of oxygen supply decreased the heat conductivity.
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Shinji Nambu, Masaki Oiji
1990 Volume 59 Issue 12 Pages
4366-4375
Published: December 15, 1990
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A microscopic calculation is carried out for thermal properties of ionic crystals on the basis of the thermodynamic variational principle. Self-consistent Einstein approximation is used to obtain effective force constants between constituent ions. Thermal expansion, temperature dependencies of the elastic constants and dielectric constants of ionic crystals are evaluated in terms of interatomic potentials. The results of numerical calculations for alkali halide crystals are in good agreement with experimental data.
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Tomotoshi Nishino
1990 Volume 59 Issue 12 Pages
4376-4383
Published: December 15, 1990
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Spectra of Cu 2
p XPS, XAS, valence band XPS and BIS of the high-
Tc compounds are calculated for Cu
nO
m (
n>1) clusters. Effects of the hole itinerancy as well as those of the hole correlation on these spectra are investigated. Size dependence of the spectra including the valence band XPS and BIS as well is examined by extending the calculation to linear clusters containing up to seven Cu atoms. It is concluded that the Cu 2
p XPS spectra consist generally of three groups of peaks which are assigned to |
cd10L〉, |
cd9〉 and |
cd10L2〉 final states. The last one which was not obtained by use of either a single Cu atom cluster or the impurity Anderson model appears in between the first two in energy. The main peak corresponding to the |
cd10L〉 state shifts with concentration of additional holes consistently with experimental data on Y–Ba–Cu oxides.
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Yasumasa Hasegawa
1990 Volume 59 Issue 12 Pages
4384-4393
Published: December 15, 1990
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Electrons on three dimensional lattice in external magnetic field are investigated. If the field is applied in the (1, 1, 1) direction with the flux per plaquette in each plane φ=
p⁄
q, the density of state at the chemical potential of electron filling ν=φ is found to be zero for φ
c<φ<1−φ
c. For the simple cubic lattice φ
c≈1⁄8. The total energy of electrons is lowered by applying the uniform magnetic field along the (1, 1, 1) direction with one flux unit par particle through each plane if the condition, ν
c<ν<1−ν
c(ν
c≈φ
c), is satisfied.
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Katsuhiko Takegahara, Yasunori Kaneta, Tadao Kasuya
1990 Volume 59 Issue 12 Pages
4394-4404
Published: December 15, 1990
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In order to clarify the origin of the semiconductor like behavior of U
3Ni
3Sb
4, one-electron energy band structures for the isostructural Th
3Ni
3Sb
4 and the Th
3P
4 type Th
3X
4 (X=P, As, Sb), which belong to the same space group, are calculated by the self-consistent APW method with the local density approximation. The calculated results for Th
3X
4 show that the compounds are the narrow gap semiconductor or semimetal; the valence bands are derived from the X
p states and the conduction bands from the Th 6
d states. Th
3Ni
3Sb
4 is also the semiconductor and the valence bands consist of the Ni 3
d and Sb 5
p states. Due to the mixing between the Ni 3
d and Th 6
d states, the empty Th 6
d conduction band is shifted up resulting a gap of 0.36 eV. This result explains reasonably why U
3X
4 is semimetal but U
3Ni
3Sb
4 is semiconductor with a gap of 0.2 eV.
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Katsukuni Yoshida
1990 Volume 59 Issue 12 Pages
4405-4411
Published: December 15, 1990
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A structural effect on the galvanomagnetic properties of indium containing granular inclusions of insulator has been investigated for specimens with the volume fraction
f of the inclusions ranging from 0 to 0.133, and the observation was analysed quantitatively in terms of the effective medium theory (EMT). The presence of the insulator inclusions yields a linear magnetoresistance depending strongly on
f. The behavior of Hall coefficient
RH correlates markedly with the occurrence of the linear magnetoresistance. The magnetoconductivity derived on the basis of EMT describes quite well the experimental results.
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Toshiro Takabatake, Shun-ichi Miyata, Hironobu Fujii, Yuji Aoki, Takas ...
1990 Volume 59 Issue 12 Pages
4412-4418
Published: December 15, 1990
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We present results of magnetic, transport and calorimetric measurements on U
3T
3X
4 with T=Ni, Cu, Pd, Pt and Au and X=Sn and Sb. A heavy-fermion behavior manifests itself in U
3T
3Sn
4, where the electronic specific-heat coefficient increases from 90 mJ/K
2 mol U for T=Ni and Pt to about 300 mJ/K
2 mol U for T=Cu and Au. We ascribe the mass enhancement to the dehybridization of 5
f electrons with the
d electrons derived from the T atom. On the other hand, U
3T
3Sb
4 with T=Ni, Pd and Pt shows a semiconducting behavior with a band gap of about 0.2 eV, whereas U
3Cu
3Sb
4 is a metallic ferromagnet with
Tc=91 K. In these antimonides, 5
f electrons are localized because of the weak hybridization with the 5
p electrons from the Sb atom. These results indicate that the number of 5
p electrons in the present system determines whether the system shows heavy-fermion or semiconducting behavior.
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Kohji Ohbayashi, Hideaki Tukamoto, Norio Ogita, Masayuki Udagawa, Yuji ...
1990 Volume 59 Issue 12 Pages
4419-4427
Published: December 15, 1990
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For YBa
2Cu
3O
7−δ oxides sintered at various temperatures, the infrared absorption mode of in-plan Cu(2)–O(2, 3) stretching motions shows the anomalous behavior to disappear for superconducting samples although it is allowed by the selection rule. The correlation between the infrared anomaly and superconductivity has been confirmed systematically for YBa
2(Cu
1−xCo
x)
3O
7−δ system in the Co concentration region of 0≤
x≤0.3 for samples quenched from sintering temperatures of 400, 500, 600, 700 and 800°C.
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Masayuki A. Ikeda
1990 Volume 59 Issue 12 Pages
4428-4442
Published: December 15, 1990
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Recently, we have proposed a
d-
p-
p model for cuprate superconductors (C.S.) in which doped
pπ holes itinerate and are subjected to an effective attractive interaction by exciton-like mechanisms (J. Phys. Soc. Jpn.
58 (1989) 3473) of
d-
pσ system. In this paper, we extend the theory to finite temperatures and derive an expression for
Tc as a function of doping density, assuming anisotropic Cooper pairing. We also show that the theory can be convertible to describe electron doped C.S. and discuss the pressure effect on
Tc giving a suggestion on the origin of sharp difference between hole-doped and electron-doped C.S.
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Junji Iida, Midori Tanaka, Yasuaki Nakagawa
1990 Volume 59 Issue 12 Pages
4443-4448
Published: December 15, 1990
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Magnetization measurements up to 143 kOe and susceptibility measurements have been carried out on a single crystal of hexagonal YFeMnO
4. This oxide exhibits a two-dimensional antiferromagnetic character, and shows spin-glass-like properties at low temperatures. The Weiss temperature obtained from high temperature paramagnetic susceptibility is −800 K, while the critical temperature where the thermoremanent magnetization disappears is only 60 K. This result suggests that both the magnetic frustration due to competing exchange interaction and the random charge distribution of the Fe and Mn ions play important roles in this magnetism.
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Muneaki Fujii
1990 Volume 59 Issue 12 Pages
4449-4453
Published: December 15, 1990
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The temperature variation of spontaneous magnetization in the two-dimensional ferromagnet K
2CuF
4 has been investigated by measuring the NMR frequency of
63Cu,
65Cu nuclei in the temperature region from 1.9 K down to 0.03 K. The results are analyzed by a two-dimensional spin wave theory.
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Hidetoshi Nishimori, Yôhei Saika
1990 Volume 59 Issue 12 Pages
4454-4461
Published: December 15, 1990
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The modified spin wave theory of Takahashi is applied to the antiferromagnetic Heisenberg model with next nearest neighbor interactions on the square lattice in the ground state. The result indicates existence of ordered states for any value of the ratio of the nearest and next nearest neighbor interactions in contrast to some of the other theories.
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Syuzo Tamura
1990 Volume 59 Issue 12 Pages
4462-4465
Published: December 15, 1990
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The magnetic permeability of stoichiometric or non-stoichiometric magnetite (Fe
3−yO
4) at high pressures has been measured in a piston-cylinder apparatus. The Verwey transition temperature decrease with pressure at rates of 2.7±0.1 KGPa
−1 for
y=0.000, 2.49±0.07 for
y=0.0051, 2.3±0.1 for
y=0.0063, 2.55±0.03 for
y=0.0070, 2.0±0.1 for
y=0.012, 2.0±0.2 for
y=0.019, 2.44±0.08 for
y=0.024, 2.4±0.1 for
y=0.033 and 2.15±0.08 for
y=0.034. A phonon-induced correlated electron transfer mechanism by Srivastava can explain the pressure dependence of the Verwey transition temperature. The temperature of the peak of temperature-permeability curve for each
y decreases with increasing pressure.
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Masayuki Kawakami, Masatoshi Nagahama, Shin-ichi Satohira
1990 Volume 59 Issue 12 Pages
4466-4471
Published: December 15, 1990
Released on J-STAGE: June 01, 2007
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The hyperfine fields
Hhf in the ferromagnetic alloys Co
2T1−xV
xGa (
T=Ti, Cr, Mn, Fe) were measured by NMR spin-echo technique at 4.2 K as a function of
x.
Hhf(V) on V impurity at
b sites (
x\simeq0) was determined to be −41, −40±2, −15 and −38±3 kOe for
T=Ti, Cr, Mn and Fe, respectively. We estimated from these values, assuming V to be non magnetic, the magnetic moments of the atoms in Co
2CrGa and Co
2FeGa with the use of the measured saturation moments. It was found that for the two alloys the same moments were obtained also from
Hhf(Mn) on Mn impurity instead of V by assuming that the magnetic moment of Mn impurity in these alloys is the same as the Mn moment in Co
2MnGa. The estimated moments of Cr and Fe were found to be consistent with
Hhf(Co).
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Masaya Nakamura, Hiroshi Orihara, Yoshihiro Ishibashi, Kazuhiro Hara
1990 Volume 59 Issue 12 Pages
4472-4475
Published: December 15, 1990
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We observed ferroelastic domain of LaNbO
4 crystals by micro-Raman spectroscopy utilizing a specific band (107 cm
−1 A
g mode) with the polarization condition. We found the variation of the Raman intensity corresponding to the ferroelastic domain structure, which is caused by the rotation of crystallographic axes in each domain. The results were in accordance with the optical microscope image with a good reproducibility, proving the feasibility of micro-Raman spectroscopy in the study of domain structures.
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Katsumi Hamano, Takeshi Sugiyama, Hideaki Sakata
1990 Volume 59 Issue 12 Pages
4476-4487
Published: December 15, 1990
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The low frequency dielectric constant of thiourea exhibits a sharp peak reaching 10
4∼10
5 at 161.6 K (
Tx) in the ferroelectric phase. From the study of the effects of dc and ac fields on this anomaly, we infer that the anomaly is produced by domain wall motion. While the static dielectric constant tends to diverge toward
Tx, the dielectric relaxation time never shows a slowing down. This fact and the result of switching experiments suggest strongly that the anomalous increase in the dielectric constant is caused not by the softening in the restoring force acting on domain walls, but by the anomalous increase in the domain wall density. A tentative model is proposed which is capable of explaining this anomalous phenomenon.
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Katsuhiko Fujii, Hiroshi Mori, Takeo Matsubara
1990 Volume 59 Issue 12 Pages
4488-4493
Published: December 15, 1990
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The peculiar temperature dependence of a remanent polarization in (NH
4)
2SO
4–K
2SO
4 mixed crystal which changes the sign at low temperature has been studied by extending the unified model in the ferroelectric crystals to the ferrielectric crystals consisting of two sublattices. The phase transition in this crystal system has been analyzed on the basis of an idea that two kinds of NH
4+ ions, NH
4+(I) and NH
4+(II), with different dipole moments form two sublattices. In the mixed crystal, NH
4+(II) with larger dipole moment than NH
4+(I) is replaced preferentially by K
+ ion with no dipole moment. We consider that the replacement of ions produces modifications in the two kinds of potential in each sublattice, two kinds of ferroelectric intrasublattice interactions and weak antiferroelectric intersublattice interaction, leading to the peculiar thermal property of the ferrielectric phase.
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Takeshi Kubota, Hitoshi Kondo, Kazuhiro Watanabe, Yasukazu Murakami, Y ...
1990 Volume 59 Issue 12 Pages
4494-4502
Published: December 15, 1990
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The three dimensional electron-positron momentum density in niobium has been reconstructed from measurements of two dimensional angular correlation of positron annihilation radiations (2D-ACAR) followed by the image reconstruction technique based on a direct Fourier transformation. We determined the position of the Fermi surface sheets;
Γ-centered hole octahedron, multiply connected jungle-gym arms and
N-centered hole ellipsoids. The Fermi surface topology is in good agreement with the theory.
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Satoshi Ideshita, Yasuaki Masumoto
1990 Volume 59 Issue 12 Pages
4503-4510
Published: December 15, 1990
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We studied the ultrafast optical nonlinearities in highly excited GaAs quantum wells by measuring time-resolved absorption. In the time-resolved absorption experiment, two-step absorption saturation at the first-subband exciton resonance was observed. The first-step of the absorption saturation corresponds to bleaching without shift due to phase space filling (PSF) of free electron-hole pairs, and the second-step corresponds to blue shift without change in bleaching due to the exchange (E) and PSF of excitons themselves. The absorption saturation at the higher subband excitons is not due to screening, but is due to the PSF and E of excitons.
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Josef Kudrnovský, Shyamal K. Bose, Ole Krogh Andersen
1990 Volume 59 Issue 12 Pages
4511-4519
Published: December 15, 1990
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The electronic structures of fcc and bcc phases of sputter-deposited Fe–Cu and Fe–Ag alloy films have been studied using the tight-binding linear muffin-tin orbital method in conjunction with the coherent potential approximation. A simple treatment of the X-ray photoemission spectra based on the electronic density of states (DOS) and the atomic photoionization cross-sections of alloy constituents, is presented. The calculated XPS results are in good agreement with the recent experimental data on these alloys.
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Tadao Ishii
1990 Volume 59 Issue 12 Pages
4520-4525
Published: December 15, 1990
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An investigation of quasi-elastic light scattering by hopping particles is made on the basis of the relaxation mode theory. The prediction by Klein that the scattering cross section gives a nonzero value at zero wave-vector transfer when the polarizability depends on lattice site is confirmed in a sublattice system. The depolarized scattering, found in some superionic conductors, is also discussed in terms of the polarizability fluctuation of pairs of mobile and adjacent deformed immobile ions.
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Masayuki Watanabe, Tetsusuke Hayashi, Riso Kato
1990 Volume 59 Issue 12 Pages
4526-4533
Published: December 15, 1990
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Luminescence spectra of PbI
2 grown from the vapor phase have been investigated at 2 K. A broad emission is observed in the energy region below the exciton absorption edge where an absorption tail spreads toward lower energy. Measurements of the luminescence decay reveal that the decay curve consists of a fast and a slow components. The slow component is supposed to be the recombination of donor-acceptor pairs. The fast component is attributed, from its spectral profile and the dependence of the decay time on the emission energy, to radiative decay of excitons localized by potential fluctuations caused by lattice imperfections. The sample dependence of the luminescence is briefly discussed in relation to the reflection spectra.
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Minoru Itoh, Nobuhito Ohno, Satoshi Hashimoto
1990 Volume 59 Issue 12 Pages
4534-4541
Published: December 15, 1990
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The self-trapped exciton (STE) luminescence of mixed K
1−xRb
xI crystals has been investigated by using D
2 lamp and synchrotron radiation as light sources at 11 K. The results show that the σ emission band is kept well over the whole composition range, and its decay time changes continuously from 2.0 ns in KI to 4.1 ns in RbI. It is found that the virtual-crystal model is quite valid for the singlet STE state which is responsible for the σ luminescence. The π emission band of KI is closely connected to the
Ex band, not the π band, of RbI with increasing
x. The π band of RbI disappears in the region
x<0.4. These facts are compatible with a recent theoretical model indicating that at equilibrium the lowest triplet STE is situated off-center. A brief discussion of the exciton relaxation into STE states in alkali halides is presented.
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Hiroya Eguchi, Masamitsu Hirai
1990 Volume 59 Issue 12 Pages
4542-4546
Published: December 15, 1990
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The initial annealing at low temperature,
e.g. 443 K and 373 K, increased slightly the absorption around the top of the fundamental absorption band at ∼6 eV, while at high temperature,
e.g. 463 K, increased largely the absorption near the top. The light illumination in the edge of the band at 90 K increased the absorption around the tail (∼3 eV) of the band, while depressed that around the top. This light illumination brought the identical absorption shape independent of the initial annealing temperature. Once the light illumination was made, spectral variations under repetitions of further thermal annealing at 463 K and light illumination at 90 K were reversibly reproduced in several times. It was made clear that the thermal annealing and the light illumination caused not only the edge shift, but total change of absorption band shape which arose from heavy distortion of the layer structure of films.
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