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Yasuhiro Akutsu, Miki Wadati
1987 Volume 56 Issue 3 Pages
839-842
Published: March 15, 1987
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A new invariant polynomial for knots and links is constructed from a solvable vertex model describing a critical statistical system. Various implications and the possible generalizations are discussed in connection with the recent development in the study of critical phenomena in two dimensions.
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Tsuguhiro Tamaribuchi
1987 Volume 56 Issue 3 Pages
843-846
Published: March 15, 1987
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A two-dimensional Ising model with quenched bond disorder is mapped to a generalized Gaussian model (GGM) with randomness. In a perturbation expansion theory on the GGM with respect to a suitably chosen virtual regular system, it is shown that the replica method yields the exact result, and that critical divergences appearing spuriously in each term in the expansion are renormalized with certain self-consistent equations to give a finite value of the internal energy when the corresponding regular model exhibits a phase transition. The method used here is a generalization of the coherent potential approximation (CPA), and is applicable to a variety of random models to which corresponding regular models are soluble.
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Toshihiro Kawakatsu, Akira Ueda
1987 Volume 56 Issue 3 Pages
847-850
Published: March 15, 1987
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An exothermic isomerization reaction expressed as
A↔
B is studied with the molecular dynamics method for a system of about 10,000 hard disks. Two types of pattern formations are observed during the relaxation processes from initial nonequilibrium states: one is a rapid and homogeneous pattern formation like a spinodal decomposition; and the other is a nucleation and growth process. In the latter case, the radius of the domain grows linearly with time. A suggested growth mechanism for this process is presented.
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Takato Hirayama, Shinji Kobayashi, Atsushi Matsumoto, Shunsuke Ohtani, ...
1987 Volume 56 Issue 3 Pages
851-854
Published: March 15, 1987
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The first observation of resonant structures is reported in the double ionization cross section in Ba
+ as a function of electron-impact energy, which are attributable to the 4d-ionization and the 5s-ionization followed by the autoionization. A brief description of the experimental method and procedures is presented. A discussion is also presented to provide a solid foundation to the identificaticn of the indirect processes concerned. Experimental results are compared with tentative results of the calculation using the distorted-wave Born exchange approximation by Younger.
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Takashi Karasudani
1987 Volume 56 Issue 3 Pages
855-858
Published: March 15, 1987
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An experimental study on the flow of an eccentric Couette-Taylor system is presented. In the system, the position of a fixed outer cylinder can be adjusted in relation to a rotating inner cylinder. The following results were obtained: when the displacement parameter was 0<ε<0.6, ε the ratio of the distance between the axes of the inner and outer cylinders to the average gap between these cylinders, a non-axis-symmetric Taylor vortex flow was observed. In particular, for ε>0.3 the flow pattern of a no-axis-symmetric Taylor vortex flow was different from that of a concentric system. For ε>0.6, there was no steady vortex flow. A pre-vortex flow changed drastically at about ε=0.3, and a confined eddy occured for ε>0.3.
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Yutaka Kamada, Hideki Arimoto, Shuichi Yamada, Keisuke Nagashima, Akio ...
1987 Volume 56 Issue 3 Pages
859-862
Published: March 15, 1987
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Bursts of impurity radiation in the visible spectral region are observed in the sustainment phase of the STP-3M reversed-field-pinch plasma. The phenomena occur simultaneously with enhancement of the toroidal magnetic flux relevant to the dynamo action and sudden increase of the ion density in the peripheral region of the plasma. Compared with calculated results using a time dependent 0-D corona model, the measured bursts of impurity radiation interpret the enhancement of impurity influx due to the plasma/wall interactions accompanied by the dynamo action.
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Seiichiro Suga, Hideaki Kasai, Ayao Okiji
1987 Volume 56 Issue 3 Pages
863-866
Published: March 15, 1987
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On the basis of the self-consistent ladder approximation, the Kondo effect in the weakly localized regime is investigated, particularly concerning the temperature dependence of the conductivity. It is shown that the conductivity in the disordered systems with a magnetic impurity decreases more rapidly by decreasing the temperature in the weakly localized regime through the interplay between the Anderson localization and the Kondo effect.
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Koh-ichi Ueda, Yoshio Kitaoka, Hiroshi Yamada, Yoh Kohori, Takao Kohar ...
1987 Volume 56 Issue 3 Pages
867-870
Published: March 15, 1987
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We present a study of
29Si and
63Cu Knight shifts in the superconducting CeCu
2Si
2. The shifts
K⁄⁄, parallel and
K⊥ perpendicular to the tetragonal
c-axis were obtained from the anisotropic
29Si NMR sectrum.
K⊥ shows a rapid decrease below
Tc(
H)=0.66 K, while the change of
K⁄⁄ is not well resolved.
K⊥ at 0.2 K decreases to 40%of the value at
Tc(
H). Furthermore, the distinct decrease of
K⁄⁄ and
K⊥ has also been observed for
63Cu below
Tc. The strong reduction of the shift, which is independent of the direction of the crystallographic axis, supports the model of even-parity pairing without significant spin-orbit scattering by impurities, although the energy gap has an anisotropic nature, as is demonstrated by the nuclear relaxation study.
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Sadao Nakajima
1987 Volume 56 Issue 3 Pages
871-872
Published: March 15, 1987
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A theoretical study is made of a multilayer superconductor consisting of alternate conducting and insulating layers. The insulating layer is assumed to be so thin that through its electronic polarization there act interlayer as well as intralayer attractive forces between conduction electrons, giving rise to the possibility of anisotropic singlet pairs. The model might be relevant to the recently discovered organic superconductor β-(BEDT–TTF)
2I
3.
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Masashi Takigawa, Hiroshi Yasuoka, Gunzi Saito
1987 Volume 56 Issue 3 Pages
873-876
Published: March 15, 1987
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The proton spin lattice relaxation rate (1⁄
T1) in the superconducting state of (TMTSF)
2ClO
4 has been measured at zero magnetic field using the field cycling technique. It was found that the enhancement of 1⁄
T1 just below
Tc, commonly observed in typical BCS superconductors, was absent and 1⁄
T1 varied as
T3. These results indicate that the superconductivity in this system is associated with the anisotropic order parameter vanishing along lines on the Fermi surface.
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Yasumasa Hasegawa, Hidetoshi Fukuyama
1987 Volume 56 Issue 3 Pages
877-880
Published: March 15, 1987
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The NMR relaxation rate,
T1−1, is calculated for the various possible types of anisotropic superconductivity in quasi-one-dimensional systems proposed by the present authors for the (TMTSF)
2X family. A comparison with recent experiment by Takigawa, Yasuoka and Saito on (TMTSF)
2ClO
4 indicates that the superconductivity of this family belongs to a novel type with the order parameter having lines of zeros on the Fermi surface.
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Masatoshi Imada
1987 Volume 56 Issue 3 Pages
881-884
Published: March 15, 1987
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The spin 1/2 triangular antiferromagnet with random exchange interaction is investigated using the finite size calculation. It is shown that the susceptibility diverges with a small randomness as
T→0, where
T is the temperature. The enhancement of the susceptibility by the randomness at low temperatures becomes larger when the Ising-like anisotropy of the exchange interaction increases. The possible connection of the divergent susceptibility to the spin glass-like order in the ground state is also pointed out.
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Kiyoichiro Motoya, Torsten Freltoft, Peter Böni, Gen Shirane
1987 Volume 56 Issue 3 Pages
885-888
Published: March 15, 1987
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Previous measurements of susceptibility and NMR relaxation suggested that the intermetallic compound YMn
2 transforms from a local moment magnet to an itinerant electron magnet at
TN∼100 K. An anomalous large volume change observed at
TN also suggests the collapse of the local magnetic moments above
TN. These conjectures have been confirmed by polarized neutron scattering techniques. Spatial correlations as well as the amplitude of the local magnetic moments above the Néel temperature show the characteristic features of weakly itinerant electron magnets.
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Klaus W. Kehr, Kazuo Kitahara
1987 Volume 56 Issue 3 Pages
889-892
Published: March 15, 1987
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The spin depolarization of a particle in quantum states is considered using a model of two sites, having different transverse magnetic fields, and between which the particle can tunnel. The ensemble average is performed with random distributions of the magnetic fields. A Gaussian decay law is obtained with the exponent reduced by a factor 2, for all times when the system is prepared in suitable eigenstates and for longtimes with arbitrary preparation. The apparent contradiction to van Vleck’s theorem is resolved.
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Mikio Shimizu
1987 Volume 56 Issue 3 Pages
893-896
Published: March 15, 1987
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It can be shown by molecular model building and semi-empirical calculation that a complex of four nucleotides (C4N) composed of three anticodonic bases and a discriminator base can discriminate its cognate amino acid by the lock and key relationship. Possible evidence for the detection of such complexes (the C4N and the C4N-amino acid complexes) are presented by using fast atom bombardment-mass spectroscopy.
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Kimiaki Konno, Hidetaka Ito
1987 Volume 56 Issue 3 Pages
897-904
Published: March 15, 1987
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Nonlinear interactions between solitons for the Korteweg-de Vries and the Boussinesq equations are considered by extending analytically one of the independent variables into complex where soliton solutions can be discussed by using poles in the complex plane. It is found that there are three types of poles and that both collisions of solitons running in the same direction and head-on collisions can be well explained on the basis of the behavior of these poles.
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A. C. Bryan, J. Miller, A. E. G. Stuart
1987 Volume 56 Issue 3 Pages
905-911
Published: March 15, 1987
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We present simple constructions of the multisoliton solution of the sine-Gordon equation (i) as a nonlinear combination of asymptotic (i.e. constant speed) solitons and (ii) as a linear superposition of accelerating kinks. We argue that the latter provides a more consistent interpretation of a multisoliton solution as an interaction between its asymptotic components.
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Kiyomi Okamoto
1987 Volume 56 Issue 3 Pages
912-917
Published: March 15, 1987
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We calculate the correlation function 〈
SizSjz〉 in the ground state of one dimensional spin-1/2 alternating antiferromagnetic Heisenberg model, taking the
XY-like anisotropy into consideration. We use the phase Hamiltonian method developed by Nakano and Fukuyama and apply the self-consistent harmonic approximation to the non-harmonic terms in the phase Hamiltonian. The long-distance behavior of the correlation function is〈
SizSjz〉∼(
x⁄ξ)
−1⁄2 exp (−
x⁄ξ), where
x is the distance between the
i-th and
j-th spins. The correlation length ξ is proportional to the inverse of the energy gap between the ground state and the first excited state. The results are compared with those of the exact numerical analysis of finite size systems and the Monte Carlo simulations.
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Tatsuya Uezu, Kazuko Kawasaki
1987 Volume 56 Issue 3 Pages
918-932
Published: March 15, 1987
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The Ising model on a triangular lattice with antiferromagnetic nearest neighbor and ferromagnetic next nearest neighbor interactions is investigated by treating the master equation by molecular field approximation(MFA) and the cluster decoupling approximation(CDA). For the fully frustrated case, CDA gives no phase transition in contrast with the MFA result which gives the finite Néel temperature. The change of states (i.e., phase transition) is explained by words of bifurcation theory and the relaxation process is investigated by studying the flow in the space of sublattice magnetizations in each approximation.
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Takahito Kaneyoshi
1987 Volume 56 Issue 3 Pages
933-941
Published: March 15, 1987
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An effective-field theory of spin-1 Ising model with random bond and crystal-field interactions is developed. The general expressions of the thermodynamic quantities, especially for the initial susceptibility, are obtained. For a particular case with a random crystal-field distribution, thermal behavior of paramagnetic susceptibility are studied for a honeycomb lattice. Owing to the simplicity, the present method can be used to study thermodynamic properties of the random systems.
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Jae Min Hyun, Jae Chun Hyun
1987 Volume 56 Issue 3 Pages
942-948
Published: March 15, 1987
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The transient buoyant convective process of an initially isothermal fluid in a closed vertical cylinder for large Rayleigh numbers is studied. The thermal forcing is impressed on the interior fluid, through the finitely conducting vetical sidewall, by a sudden increase in the ambient temperature. The idealized theoretical model due to Rahm for one-dimensional temperature evolution in the core is briefly recounted. Finite-difference numerical solutions to the time-dependent Navier-Stokes equations are acquired. These solutions are qualitatively consistent with the physical picture proposed by Rahm. The transient phase of the core temperature field is divided into a stratified region and an isothermal region by a propagating temperature front. The fluid pumping mechanism by the vertical sidewall boundary layer drives a counterclockwise meridional circulation. The global adjustment process is accomplished over the characteristic time scale derived by Rahm. The difficulties and applicability of the theoretical model are examined.
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Sadayoshi Toh
1987 Volume 56 Issue 3 Pages
949-962
Published: March 15, 1987
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Statistical properties of the chaos of the Kuramoto-Sivashinsky equation are investigated numerically and theoretically. It is found that the chaos consists of spatially localized structures (pulses) and the distances between adjacent pulses have the distribution which is localized around a single peak through the mechanism of creation and annihilation of pulses. The energy spectrum is calculated by a statistical model in which the pulses with a fixed shape are lined up in the way that each distance is independent of others. This model reproduces a peak near the wavenumber
k=1⁄\sqrt2 as well as the flat part near
k=0 in the energy spectrum. The linear dependence of the amount of chaos on the system parameter is discussed with this model.
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Kanya Kusano
1987 Volume 56 Issue 3 Pages
963-972
Published: March 15, 1987
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By means of 3D magnetohydrodynamic simulations, the relaxation process in the finite β reversed-field pinch (RFP) is investigated. It is confirmed that the nonlinear reconnection process is the dominant mechanism of the RFP relaxation even in the system of finite β. The nonlinear reconnection rate is almost halved compared with that in the zero β case. The relaxed state of finite β is dynamically achieved. This state has a flat pressure profile and is well approximated by the Bessel-function model in the central region. The simulation result agrees with the partially relaxed state model. The β-limit is estimated based on the Suydam criterion, and consequently, it is found that the stable area on the F-θ diagram is narrowed as the heat loss decreases.
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Masatoshi Yagi, Masahiro Wakatani, Akira Hasegawa
1987 Volume 56 Issue 3 Pages
973-981
Published: March 15, 1987
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Scale transformation introduced by Connor and Taylor is applied to the model equations for the resistive interchange mode (g mode) and the resistive drift wave in a high shear helical system. The electron pressure gradient term in Ohm’s law is essential in deriving the present results. Scaling of collisionless transport along stochastic fields due to the g modes coincides with the result based on the mixing length theory. When the resistive drift waves are dominant, the predicted transport is κ
2⁄
s2 times the pseudo-classical transport, where κ is the characteristic length of density gradient and
s is the shear parameter. The transport coefficient which results from the g mode and/or the resistive drift wave turbulence increases towards the edge. The density fluctuation for the resistive drift wave turbulence scales as (
Te⁄
n)
1⁄2κ which also increases toward the edge in most toroidal plasmas.
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Shin Takeuchi, Kaoru Kimura
1987 Volume 56 Issue 3 Pages
982-988
Published: March 15, 1987
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Electron and X-ray diffractions from a metastable phase in an Al
79.5Mn
20.5 alloy, formed by a rather slow quenching of the melt, have been consistently interpreted by the decagonal quasicrystalline phase (L. Bendersky: Phys. Rev. Lett.
55 (1985) 1461). A structural model of the phase is proposed, in which two unit cells with the Penroserhombic prisms (edge length 4.30 Å and height 4.15 Å), containing five and three atoms, are packed in a plane, satisfying a face-matching rule to form a Penrose-type lattice with a ten-fold symmetry. These quasicrystalline layers stack periodically with an ordered modulation at every three layers.
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Yoshiaki Kogure, Tadayoshi Tsuchiya, Yosio Hiki
1987 Volume 56 Issue 3 Pages
989-998
Published: March 15, 1987
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A simulation has been made for a screw dislocation in argon and xenon model crystals with various sizes. The number of atom rows in the crystal was 360–1400, and the Lennard-Jones (12–6) interatomic potential truncated at the third neighbors was adopted. The ordinary relaxation method was used to obtain the stable configuration of atoms in the crystal. It was found that the dislocation split into two Shockley partials, and the configuration of the partials depended on the boundary condition of the crystal surface. A method of modified boundary condition was proposed to control the effect of the surface. The split dislocations were able to stably exist when their separation was in a definite range, which was well understood by considering the balance of three forces: the interaction force between partials, the force due to stacking fault, and the image force from the crystal surface. By taking the limiting value of the separation distance for the crystal of infinite size, the stacking fault energy was estimated to be 0.74±0.10 and 1.09±0.14 erg/cm
2 for argon and xenon.
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Toshio Kosugi, Takao Kino
1987 Volume 56 Issue 3 Pages
999-1009
Published: March 15, 1987
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In order to obtain the information on the force-distance relation for the interaction between a dislocation and a solute atom, the amplitude-dependent internal friction was measured at 1.7–30 K on Al-100 at ppm Zn and Al-50 at ppm Zn single crystals.The temperature dependence of the applied strain under a constant decrement was exactly the same for the two crystals. The data were analized by using the thermally assisted break-away theory for pinned dislocations with assuming several forms of the interaction potential. A modified Cottrell potential was considered, in which the interaction force was cut off at a critical distance close to the center of dislocation. This model was found to be able to explain the temperature dependence of the applied strain satisfactorily, and the critical distance was estimated to be 1.4 Å.
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Jun’ichir\={o} Nakahara, Takaki Ichimori, Shigeru Minomura, Hiro ...
1987 Volume 56 Issue 3 Pages
1010-1016
Published: March 15, 1987
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Raman spectra have been measured in Al
xGa
1−xAs as a function of alloy composition and pressure. The Raman spectra are interpreted as a 2-mode behavior (persistence type) for LO and TO phonons and a 1-mode behavior (amalgamation type) for LA and TA phonons as being theoretically predicted. With increasing
x, the AlAs-like LO and TO modes shift to higher frequencies and GaAs-like modes shift to lower frequencies. Under high pressure these modes shift to the higher frequencies. We analyze the Raman spectra of TO modes as the disorder activated lines from the whole Brillouin zone. The low energy structures are assigned to the disorder activated TA and LA modes by the pressure dependences of their energies and by their line shape. The spectral assignments of these modes in Al
xGa
1−xAs are consistent with their composition dependence.
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Yoshiaki Ozaki
1987 Volume 56 Issue 3 Pages
1017-1028
Published: March 15, 1987
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The intensity of neutron scattering for tunnel splitting levels of NH
4+ ion is calculated in terms of the orientationally localized states. The κ-dependence of the transition integral and the temperature dependence of the spectra are derived. In conclusion,
C3v orientation is the best model to yield the observed spectra and two big additional peaks are anticipated in
E>3 meV.
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M. Schreiber
1987 Volume 56 Issue 3 Pages
1029-1042
Published: March 15, 1987
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The energy of ground and electronically excited states of a static Peierls-Hubbard-model Hamiltonian is exactly determined for a system of three electrons on three equivalent sites. For sufficiently strong electron-phonon coupling the ground state is characterized by a charge transfer accompanied by a strong lattice distortion. Strong electronic correlation prevents this kind of symmetry breaking, but a Jahn-Teller distortion is then found due to the spin frustration. The transition between these phases and the existence of metastable states is analysed in detail.
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Akio Yamanaka, Itaru Tatsuzaki
1987 Volume 56 Issue 3 Pages
1043-1050
Published: March 15, 1987
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The longitudinal and transverse acoustic modes in squaric acid were measured by Brillouin scattering as functions of uniaxial stress and temperature. The compressible (
c22) and shear (
c44) elastic stiffnesses related to interlayer bondings were obtained from these studies. Temperatture dependence of these acoustic frequencies has been discussed by the aid of the uniaxial stress dependence, and mainly ascribed to the variation of interlayer distance due to thermal expansion and the pure temperature effect which is present even if the crystal is constrained to constant volume.
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Ryusuke Nishitani, Yoshiro Sasaki, Yuichiro Nishina
1987 Volume 56 Issue 3 Pages
1051-1057
Published: March 15, 1987
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The staging kinetics in H
2SO
4-GIC’s has been investigated experimentally by time-and space-dependent Raman scattering measurements. The stage transition from stage
n to
n−1 begins at the interface between the intercalant reservoir and the
a-face of the graphite crystal. The lower stage-(
n−1) domains emerge at the interface and proceed toward the inner region of the crystal. A narrow phase-boundary between different stage domains exists in the localized region and move toward the inner region as the stage transformation progresses. The present results support the model [R. Nishitani, Y. Uno and H. Suematsu: Synth. Met.
7 (1983) 13] that the stage transformation proceeds via propagation of the boundary between well-staged regions. The origin of the stage disorder is also discussed.
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Shin’ichi Takeda, Hideo Okazaki, Shigeru Tamaki
1987 Volume 56 Issue 3 Pages
1058-1063
Published: March 15, 1987
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The measurements on specific heats of liquid In–Te and Se–Te alloys have been carried out to explore the mechanism of metal-nonmetal transition in the liquid state. A large temperature dependence of the specific heats has been observed around In
2Te
3 for In–Te alloys and in the Te rich region for Se–Te alloys, respectively. These large specific heats are fully explained in terms of Schottky-type specific heats due to the transition from non-metallic state to metallic one in addition to Dulong-Petit’s values. The specific heat of liquid Se–Te system in the Se-rich region is, on the otherhand, not so much dependent on temperature and is almost equal to 8 cal/g-atom·deg. From these, it is inferred that in liquid Se–Te alloys there exists an endothermic reaction due to the recombination of bonding in the Te-rich region, while there exists neutral broken bonds in the Se-rich region.
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Masako Akai, Hisazumi Akai, Junjiro Kanamori
1987 Volume 56 Issue 3 Pages
1064-1077
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A self-consistent calculation of the electronic structure of light impurities (μ
+, H, He, …, F, Ne) at substitutional and interstitial sites in ferromagnetic iron is presented. The calculation is based on the KKR method with the impurity potential self-consistently determined by use of the local spin density functional formalism. The adiabatic potential of impurity around the center of a substitutional site is also calculated within the same framework with the result that it takes a maximum value at the center in the cases of μ
+, H, B, C, N, O and F, a minimum one in the cases of He, Li and Ne and is quite flat in the case of Be. A qualitative argument is given on the mechanism underlying the variation of the adiabatic potential with atomic number. Experimental data on the hyperfine interaction of impurity nuclei are discussed in the light of these calculations to conclude plausible locations of impurities.
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Satoshi Watanabe, Hiroshi Kamimura
1987 Volume 56 Issue 3 Pages
1078-1091
Published: March 15, 1987
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The electronic structures of substitutional 3d transition metal (TM) impurities Ti
2+ to Cu
2+ in ZnS have been calculated from the first principles in the cluster method. The TM impurity states are found to be described well by a relatively large cluster consisting of 59 atoms. All impurity states appear in the energy gap region of ZnS and have a strong TM 3d character except those of Cu
2+. The effects of multiplet struclure have been included by a parameter-free approach which connects the first principles results with the ligand field theory. The low-lying multiplets of 3d TM impurities in ZnS are reproduced well by the present theory.
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Tatsuya Okada, Satoru Ohno
1987 Volume 56 Issue 3 Pages
1092-1100
Published: March 15, 1987
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The electrical conductivities of liquid Fe–Te, Co–Te and Ni–Te systems increase with increasing transition metal (TM) concentration. The values of conductivity obtained at 1200°C are 2980, 3780 and 5260 ohm
−1·cm
−1 for the composition FeTe, CoTe and NiTe, respectively. However, the conductivities of liquid Ti–Te, V–Te and Cr–Te alloys decrease with increasing TM concentration. Moreover, the liquid Mn–Te system exhibits a sharp minimum at the composition MnTe. The values of conductivity obtained at 1200°C are 1710 and 22 ohm
−1·cm
−1 for the composition CrTe and MnTe, respectively. The corresponding data for magnetic susceptibility indicate that the density of
d-like states at the Fermi level
EF is fairly large for liquid CoTe and NiTe and small for liquid MnTe. The conductivities of liquid TM–Te alloys are closely related to the density of
d-like states at
EF.
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Kunihiko Yamaji
1987 Volume 56 Issue 3 Pages
1101-1110
Published: March 15, 1987
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The effect of the Umklapp process matrix elements of the SDW periodic potential is studied on the basis of an anisotropic two-dimensional band modeling the Bechgaard salts. The matrix elements are calculated by using one-electron eigen wave functions obtained in the normal state in the magnetic field with due regard to the dimerization along the conducting
a-axis. When the number of holes in the band slightly deviates from the stoichiometric value due to impurities etc., Umklapp matrix elements produce small gaps of order 0.03 meV apart from the bigger Landau band gaps in the energy spectrum. These gaps pulsate reaching zero with a period close to the small period observed in the phenomenon of the title. Plausible arguments are given to explain to phenomenon in terms of the Zener tunneling of current carriers through these pulsating small gaps.
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Kimitoshi Kono
1987 Volume 56 Issue 3 Pages
1111-1122
Published: March 15, 1987
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A new experimental method has been developed for studying coupled plasmon-ripplon resonances of electron crystal formed on the surface of liquid helium. Measurements are done at temperatures between 0.45 and 0.9 K and electron areal densities from 5×10
8 to 1.2×10
9 cm
−2. Resonance frequencies are quantitatively compared with the theory by Fisher, Halperin, and Platzman (FHP) and by Namaizawa. The agreement between the experiment and the FHP theory is satisfactory at low electron densities, although at high densities a modification is needed. The Debye-Waller facfor of the Wigner crystal is well explained by the Debye model, and the factor is found to have a significant contribution from the zero-point vibration of the Wigner crystal.
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Seishi Takagi
1987 Volume 56 Issue 3 Pages
1123-1126
Published: March 15, 1987
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Magnetic susceptibility of an organic ion-radical salt, triethylammonium-[TCNQ]
2, has precisely been measured in the temperature range between 4.2 and 360 K. It shows a shallow but obvious dip near 215 K. Such anomaly in the susceptibility of the salt has been found for the first time. The anomaly may result from the change of the nature of spin dynamics in the salt. The susceptibility cannot be explained in a wide temperature range including 215 K by a
simple spin-pair model.
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Makio Kurisu, Hiroshi Tanaka, Hideoki Kadomatsu, Hiroshi Fujiwara
1987 Volume 56 Issue 3 Pages
1127-1131
Published: March 15, 1987
Released on J-STAGE: May 29, 2007
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Measurements of pressure dependences of electrical resistivity ρ up to 29 kbar and magnetization up to 10 kbar have been made for CeMg and LaMg. The Néel temperature
TN decreases linearly at a rate of −0.16 K kbar
−1 up to 10 kbar and then tends to saturate at higher pressures. The magnetic susceptibility χ at 4.2 K increases with pressure. Pressure effects on ρ,
TN and χ are briefly discussed with recent theories of Kondo system. Pressure-induced structural phase transition is not found in CeMg and LaMg.
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Hidetoshi Nishimori, Kiyomi Okamoto
1987 Volume 56 Issue 3 Pages
1132-1137
Published: March 15, 1987
Released on J-STAGE: June 01, 2007
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The spin-1/2 alternating Heisenberg model with
XY-like anisotropy is studied by numerical methods. This model exhibits critical behavior in the ground state as the bond-alternation parameter δ approaches 0. The critical exponents characterizing this ground-state critical point are estimated. The results agree well with those of the analytical calculation of Nakano and Fukuyama. A logarithmic correction of the type predicted by Black and Emery is found to be consistent with numerical data in the isotropic Heisenberg model but not in anisotropic models.
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Kazuyoshi Yoshimura, Masashi Takigawa, Yoshinori Takahashi, Hiroshi Ya ...
1987 Volume 56 Issue 3 Pages
1138-1155
Published: March 15, 1987
Released on J-STAGE: June 01, 2007
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The hyperfine field,
Hhf, and the nuclear spin-lattice relaxation rate, 1⁄
T1, of
59Co and
27Al nuclei have been measured in the weak itinerant ferromagnets Y(Co
1−xAl
x)
2. The temperature and magnetic field dependence of 1⁄
T1T has been found to be well described by the self-consistent renormalization (SCR) theory of spin fluctuations. From the experimental data of the nuclear relaxation and the magnetization, the parameters characterizing the spin fluctuations in these materials were estimated. The temperature dependence of the magnetic susceptibility was calculated using these values in the framework of the SCR theory. The calculated results well reproduce the observed susceptibility, supporting the quantitative validity of the SCR theory. It has also been shown that a theoretical relation between these parameters proposed recently is consistent with the experimental data.
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Mamoru Mekata, Yoshitami Ajiro, Tomihiko Tatsumi, Hiroaki Kadowaki, Ki ...
1987 Volume 56 Issue 3 Pages
1156-1158
Published: March 15, 1987
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The spin components in the
c-plane have been measured in the ordered phases of CsCoCl
3 by the neutron polarization analysis. No appreciable
c-plane components were found in the low temperature phase as in the high temperature phase.
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Yuichi Itoh, Hideoki Kadomatsu, Makio Kurisu, Hiroshi Fujiwara
1987 Volume 56 Issue 3 Pages
1159-1164
Published: March 15, 1987
Released on J-STAGE: June 01, 2007
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The electrical resistivities of a Kondo ferromagnet CePt and of LaPt have been measured under pressures up to 32 kbar and at temperatures from 1.5 K to 300 K. With increasing pressure
p, the magnetic resistivity ρ
m increases and the absolute value of the slope of the logarithmic temperature dependence of ρ
m above the temperature
Tmax, at which ρ
m takes a maximum, increases, whereas
Tmax decreases. The Curie temperature increases with increasing
p, but the rate of increase becomes small. The correspondence between the pressure effect and the alloying effect in CeP
1−xNi
x is discussed as a function of volume, and it is pointed out that the 5d band widening is an important factor in both effects.
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Akihiko Nishida, Kazumi Horai
1987 Volume 56 Issue 3 Pages
1165-1171
Published: March 15, 1987
Released on J-STAGE: May 29, 2007
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The conduction electron spin resonance of silver foils doped with 10 ppm Au has been measured by the transmission method over the thickness range 5–66 μm in the temperature range between 18 K and 44 K at 22.7 GHz as functions of thickness and temperature. As a result of doping silver with Au, the spin-orbit parameter dominating the phonon-induced spin relaxation has not been changed significantly. On the other hand, the surface spin scattering probability ε has increased from 6×10
−4 to 2×10
−3. This increase with Au impurities has been attributed to the impurity-induced disorder of the silver surface.
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Ryogo Kubo, Takahiko Endo, Shiro Kamohara, Mitsuaki Shimizu, Masataka ...
1987 Volume 56 Issue 3 Pages
1172-1177
Published: March 15, 1987
Released on J-STAGE: June 01, 2007
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The long-time tail of the Kubo-Toyabe relaxation function of spin polarization in zero-field is examined by a variational method and a numerical simulation. The asymptotic exponential decay was found to be of the form, 0.2362 exp (−1.562ν
t), where ν is the decay constant of the perturbing Gaussian random field. This decay constant is shown to be determined by the lowest eigenvalue of a confluent hypergeometric differential equation.
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Masanori Arakawa, Toshikazu Hirose
1987 Volume 56 Issue 3 Pages
1178-1184
Published: March 15, 1987
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EPR measurements on Cu
2+ centre in WO
3 arc made at 131 K using an X-band spectrometer. The determined
g and
A parameters in the spin Hamiltonian have strong
c-axis anisotropy, as
gX=2.053,
gY=2.050,
gZ=2.415 and
AX=24.5×10
−4cm
−1,
AY=18.9×10
−4cm
−1,
AZ=−99.0×10
−4cm
−1 (Eulerian angles; θ
1=11.7°, φ
1=44.5°, ψ
1=6.5°). The ground state of Cu
2+ ion is determined to be |
x2−
y2〉 by
g-value analysis. Two models for Cu
2+ centre are discussed by comparing with previous EPR results for V
4+(3d
1) ion in WO
3; one is Cu
2+ centre associated oxygen vacancy at the nearest site along the
c-axis and the other is Cu
2+ centre located at interstitial site.
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Hideyuki Nakagawa, Takanobu Yamada, Hiroaki Matsumoto, Tetsusuke Hayas ...
1987 Volume 56 Issue 3 Pages
1185-1196
Published: March 15, 1987
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Optical absorption measurements were made on single crystals of CdI
2, in the region near the absorption edge. The intrinsic absorption edge of Cdl
2 is dominated by the well-defined structures due to indirect excitonic absorption below 30 K. With raising the temperature, these structures are smeared out into an exponential absorption tail with relatively large steepness. Another exponential component with small steepness appears on the low energy side above 100 K and grows up to surpass the former above 130 K. Absorption measurements were also made on very thin crystals. A prominent peak and a shoulder were found at 3.693 and 3.80 eV. The small steepness component is considered as the low energy tail of the 3.693 eV absorption band. Discussions are made on the excitonic states responsible for these absorption structures and tails as well as on the exciton relaxation in the CdI
2 crystal.
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Masatoshi Tanaka, Wakahiko Kaneko, Susumu Kurita, Akio Yamada, Hirohit ...
1987 Volume 56 Issue 3 Pages
1197-1202
Published: March 15, 1987
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Piezoreflectance spectra of quasi-one-dimensional [Pt(en)
2][Pt(en)
2Cl
2](ClO
4)
4 crystals have been measured under a uniaxial stress along the chain axis, in the photon energy range from 1.5 eV to 8 eV. Under a compressive stress, a charge-transfer transition between platinum
dz2 bands shifts to lower energies, whereas transitions from halogen
pz bands to a platinum
dz2 band shift to higher energies. Moreover, oscillator strength of the charge-transfer transition increases. These results yield a stress-dependence of band parameters in the one-dimensional
dz2-
pz bands which is well explained by the band scheme obtained by the tight-binding approximation.
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Chul Woo Lee, Takashi Kushida
1987 Volume 56 Issue 3 Pages
1203-1212
Published: March 15, 1987
Released on J-STAGE: June 01, 2007
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Photoabsorption and photoreflectance spectra have been measured in a semiconducting layer-compound GaSe in the exciton energy region at temperatures between ∼300 K and ∼80 K. The photomodulation at the frequency of 10 Hz∼200 kHz has been found to be useful as the means of thermomodulation without a contact. A high-frequency photoabsorption experiment at the modulation frequency of 5 MHz has also been performed using a pair of picosecond dye lasers. In this experiment, time behavior of the photomodulation signal has been determined from the dependence of the signal intensity on the delay time of the probe pulse and also on the phase of the lock-in amplifier. The dominant modulation mechanisms of this experiment have been identified as the spectral variation due to the reduction of the built-in surface electric field and the exciton-exciton collision.
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