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Kazuo Saitoh, Satoshi Takada, Kenn Kubo
1987 Volume 56 Issue 11 Pages
3755-3758
Published: November 15, 1987
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We have studied the Spin 1 antiferromagnetic chain with both bilinear and biquadratic exchange interactions. The spin correlations have been calculated by means of the transfer matrix method based on the Trotter formula. The mass gap (
m(0)) at the ground state has been investigated as a function of the ratio λ between bilinear and biquadratic interactions. The result suggests that the gapless ground state persists in a finite range of λ, i.e., λ
c<λ<λ
1, with λ
c=0.5 and λ
1>1 which is consistent with the exact solution at the completely integrable point (λ=1). The calculated mass gap (
m(0)) has been fitted to a Kosterlitz-Thouless (KT)-type for λ<λ
c (
m(0)=
A exp [−
B⁄(λ
c−λ)
σ]) producing the results σ=0.49±0.04 and λ
c=0.49±0.03.
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Shoichi Kai, Hidehiko Fukunaga, Helmut R. Brand
1987 Volume 56 Issue 11 Pages
3759-3762
Published: November 15, 1987
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The multiplicative stochastic process is studied in the electrohydrodynamics of nematic liquid crystal. The dependence of the threshold for the first instability on noise intensity is not monotonous and shows three bends suggesting the change of the noise dependence due to the onset of different spatial structures. This dependence is drastically varied by changing the correlation time of noise.
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Koya Abe, Katsuya Amako, Yasuo Arai, Yuzo Asano, Herbert Boerner, Masa ...
1987 Volume 56 Issue 11 Pages
3763-3766
Published: November 15, 1987
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A result of the search for the top quark in
e+e− annihilation into hadrons at \sqrt
s=50 GeV is presented. The experiment has been performed using the VENUS detector at TRISTAN. No evidence has been found for the production of the top quark. From the study using the event shape of the multihadron events, the upper limit of the production cross section is found to be 16 pb at the 95% confidence level.
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Koya Abe, Katsuya Amako, Yasuo Arai, Yuzo Asano, Herbert Boerner, Masa ...
1987 Volume 56 Issue 11 Pages
3767-3770
Published: November 15, 1987
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The differential cross sections for
e+e−→
e+e− and
e+e−→γγ have been measured at the highest energy of \sqrt
s=52 GeV in
e+e− collisions.The process
e+e−→
e+e− is well understood within the framework of the standard model of electroweak interactions. The reaction
e+e−→γγ is found to be in good agreement with QED. The 95% confidence limits obtained for the QED cut-off parameters are
Λ+>61 GeV and
Λ−>72 GeV for
e+e−→γγ.
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Fujihiro Hamba
1987 Volume 56 Issue 11 Pages
3771-3774
Published: November 15, 1987
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The transport equation for the turbulent energy dissipation rate is investigated using a two-scale direct-interaction approximation. The time integral of a two-time velocity correlation is examined to obtain a statistical model for the dissipation equation. It is shown that the familiar production term in the standard
K−ε model is not sufficient.
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Teruji Cho, James H. Foote, Yousuke Nakashima, Kameo Ishii, Hiroshi Su ...
1987 Volume 56 Issue 11 Pages
3775-3778
Published: November 15, 1987
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In the tandem mirror
GAMMA 10, (i) the enhancement of the ion confining potential, φ
c, only during the period of the thermal barrier potential φ
b-formation, has been observed first by using not only end-loss-analysers (
ELA’s) of
GAMMA 10 but an end-loss-ion-spectrometer (
ELIS) installed from
TMX-U. This results in strong end-loss-ion plugging with increased central cell density. (ii) The first experimental observation of the φ
c vs φ
b-scaling law is obtained, where φ
c increases with φ
b. This scaling law is consistently interpreted by Cohen’s theories of the weak-
ECH and the strong-
ECH in the plug region, (iii) Good agreement of the plug potential measured with the
ELA’s and the
ELIS is achieved.
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Hideo Sugai, Kazuo Kikuchi, Takayoshi Okuda, F. R. Hansen, J. P. Lynov ...
1987 Volume 56 Issue 11 Pages
3779-3782
Published: November 15, 1987
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An electromagnetic wave of ordinary mode (O-mode) at a frequency near the second electron cyclotron harmonic is obliquely incident on an overdense (ω
p>ω) large-volume plasma. Two-dimensional measurements of wave propagations suggest that this is a result of cascade mode conversion, the first conversion being from the O-mode to the X-mode at the critical density (ω=ω
p), and the second conversion being from the X-mode to the Bernstein mode at the upper hybrid resonance. For high-power incidence, electron heating takes place locally around the upper hybrid layer where the intense Bernstein-mode signals are detected. The heating is observed only for ω
p>ω, supporting the theory of cascade mode conversion.
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Yoshio Nagami, Masanori Tanaka, Seiichi Kagoshima, Koichi Kikuchi, Kaz ...
1987 Volume 56 Issue 11 Pages
3783-3785
Published: November 15, 1987
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X-ray studies show that metal-insulator transitions of the title compounds occur with no structural changes. This result suggests an appearance of spin-density waves, rather than charge-density waves, in the insulating phase.
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Mitsuo Harada, John E. Fischer, Gen Shirane, Yasusada Yamada
1987 Volume 56 Issue 11 Pages
3786-3788
Published: November 15, 1987
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In this letter we report on a neutron scattering investigation of the cooperative Jahn-Teller phase transition in RbCuCl
3. We observed strong critical diffuse scattering due to correlated fluctuations of J–T clusters. This is in sharp contrast to the previously reported scattering characteristics of CsCuCl
3 which undergoes similar J–T phase transitions. In CsCuCl
3, no critical scattering was observed, however, strong Huang scattering around Bragg reflections was observed. These results indicate that the interactions which cause cooperative J–T phase transitions in these materials may be substantially different.
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Katsumi Hamano, Hideaki Sakata, Kenji Ema
1987 Volume 56 Issue 11 Pages
3789-3792
Published: November 15, 1987
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On the basis of the free energy of an incommensurate system, a qualitative discussion is made of the time evolution of the spacing of discommensuration lattice during the first-order commensurate-to-incommensurate transition. It is shown that in the early stage of the transition when both phases coexist, the discommensuration lattice has a wider spacing
l than the spacing
le in the final equilibrium state, and that after the crystal is covered with a lattice with
l, the spacing is narrowed to
le by further nucleation of discommensurations.
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Masatoshi Imada
1987 Volume 56 Issue 11 Pages
3793-3796
Published: November 15, 1987
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A possible mechanism of superconductivity in oxide compounds is studied on the basis that hole carriers mainly occupy oxygen
p-orbits. It is shown that oxygen holes may form singlet pairs with neighboring copper holes. It is proposed that mutually attractive interaction of the singlet pairs may lead to superconductivity. Results of quantum simulations show enhancement of pairing between two oxygen holes on a two-dimensional square lattice.
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Noritaka Kuroda, Fumio Chida, Yoshiro Sasaki, Yuichiro Nishina, Masae ...
1987 Volume 56 Issue 11 Pages
3797-3800
Published: November 15, 1987
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The presence of the superconducting energy gap, 2
Δ, in YBa
2Cu
3O
6.74 has been observed directly at 45±5 cm
−1 and at 1.6 K by far-infrared absorption measurements in small particles embedded randomly in a polyethylene film. This result indicates that the gap has the minimum of 2
Δmin\simeq0.7
kTc, and thus the gap is finite along any direction in the crystal. Transverse effective charges associated with polar optical phonons at 144, 280, and 315 cm
−1 increase by a factor of 4∼5 upon a decrease in the temperature from 295 K to 1.6 K, suggesting the presence of an anomalous electron-phonon coupling in this material.
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Peter Böni, Gen Shirane, Yasuhiro Nakazawa, Masayasu Ishikawa, Sh ...
1987 Volume 56 Issue 11 Pages
3801-3804
Published: November 15, 1987
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Neutron scattering measurements on the heavy fermion system CeSi
1.76Cu
0.24 confirm a phase transition to ferromagnetic order below
Tc=8 K. The ordered moment μ=0.62±0.05 μ
B is about four times smaller than the effective moment above
Tc and agrees well with the saturation moment determined by dc-magnetization measurements. The moments lie in the basal plane of the tetragonal unit cell. The very weak critical magnetic scattering suggests a new type of local moment formation below
Tc.
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Tatsuo Kobayashi, Kiichi Amaya, Takao Kohara, Koh-ichi Ueda, Yoh Kohor ...
1987 Volume 56 Issue 11 Pages
3805-3807
Published: November 15, 1987
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Heat capacities of high-
Tc superconductors Ba
2RCu
3O
x (R=Gd, No, Er, Dy) are measured at temperatures below the respective superconducting transition temperatures. The observed sharp peaks at 2.25 K(Gd), 0.95 K(Dy), 0.55 K(Er) and 0.1 K(Ho) are associated with the magnetic ordering of the rare-earth ions in two dimensions. A co-existence of superconductivity and magnetic ordering is also confirmed down to the measured temperature of 30 mK.
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Nobuyuki Matsushita, Norimichi Kojima, Toshiro Ban, Ikuji Tsujikawa
1987 Volume 56 Issue 11 Pages
3808-3811
Published: November 15, 1987
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The intervalence charge-transfer absorption spectra in the mixed-valence complexes [Pt(en)
2][PtI
2(en)
2](SO
4)
2·6H
2O and [Au
xPt
1−xI(en)
2]SO
4·3H
2O (
x=0.03) have been investigated at 4.2 K. In these complexes, below the charge-transfer absorption edge, a weak absorption band (
A-band) has been observed for the light polarized parallel to the chain axis. When these complexes were irradiated with the light in the region of the charge-transfer transition from Pt
II to Pt
IV, the absorption coefficient of the
A-band increased remarkably, which implies that the
A-band is a photo-induced absorption band. The photo-induced effect for the
A-band in [Au
xPt
1−xI(en)
2]SO
4·3H
2O (
x=0.03) is more intense than that in [Pt(en)
2][PtI
2(en)
2](SO
4)
2·6H
2O. The
A-band suggests the existence of new excitations such as a soliton-like excitation in the electronic state of the platinum chains.
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Fukuko Yuasa, Noriko Saitoh, Éi Iti Takizawa
1987 Volume 56 Issue 11 Pages
3813-3820
Published: November 15, 1987
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The two-dimensional Toda lattice (2DTL) system is reformulated in the gauge and dual symmetric scheme. The linear Bäcklund transformation (BT), or the duality equations presented here, is solved and the dual symmetry guarantees that the general solution of these equations maintain the general solution of the nonlinear 2DTL equation.
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Masao Nomura
1987 Volume 56 Issue 11 Pages
3821-3831
Published: November 15, 1987
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Aggregate creation (or annihilation) operators of one-dimensional spinless bosons are found as operator realization of Schur-functions i.e. Young diagrams. A unitary operator is introduced to transform the aggregate boson operator into the fermion operator that also acts as an operator form of the Young diagram. The fermion operator produces, in case it acts on vacuum, the uncoupled fermion state just describable in Sato’s Maya diagram. Further, characteristic of S-function comes out in such quantum-mechanical solvable models, a boson model of the present author and a simplified Tomonaga-Luttinger model. Usefulness of the unitary operator is demonstrated also as a partial restatement of the theory of Kadomtsev-Petviashvili equation.
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Kuninosuke Imaeda, Yoshitaka Yamamoto, Takahiro Yamaguchi
1987 Volume 56 Issue 11 Pages
3832-3846
Published: November 15, 1987
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We have simulated the Oregonator by “shift type mapping” functions which approximate the strange attractor of the Oregonator (a system governed by a set of non-linear differential equations) exerted by an external periodic force. We have reproduced fairly well the bifurcation and the sequential appearance of the periodic π(
m) modes and π
p,q(
m,
m+1) modes as well as chaotic modes. The theoretical prediction of the oscillation modes using a piecewise linear mapping function agrees qualitatively with the results of the Oregonator and those using other mapping functions.
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Hitoshi Harada
1987 Volume 56 Issue 11 Pages
3847-3852
Published: November 15, 1987
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New subhierarchies of the KP hierarchy in the Sato theory, named the
m-truncated KP hierarchies (
m=1, 2, …), are presented. The simplest one of the case
m=1 is the Burgers-Hopf hierarchy, which is transformed into a system of linear equations, while other cases are into systems of linear and nonlinear equations. On account of the linear equations, the multiplicity of soliton solutions is limited up to
m for the
m-truncated KP hierarchy. It is also shown that the solution space of the
m-truncated KP hierarchy is a submanifold “
GM(
m, ∞)” of the universal Grassmann manifold
UGM, which is the solution space of the full KP hierarchy.
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Xin-Zhong Yan, Setsuo Ichimaru
1987 Volume 56 Issue 11 Pages
3853-3857
Published: November 15, 1987
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We present the case for the modified convolution-approximation scheme and show through numerical solution to the integral equations that it predicts the thermodynamic properties accurately and self-consistently for strongly coupled, classical one-component plasmas.
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Takehiko Oguchi, Hidetsugu Kitatani, Hidetoshi Nishimori
1987 Volume 56 Issue 11 Pages
3858-3864
Published: November 15, 1987
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A perturbational method is developed and applied to the numerical calculation for the energy of the ground state
Eg of antiferromagnetic Heisenberg model of finite size systems. In this method the system is divided into two subsystems and each one is treated exactly, while the interactions between the subsystems are taken into account by the second order perturbation. This process saves the memory space of computer, and moreover the relative error is very small and decreases as the size of system is increased. Actual calculations for the triangular lattice are performed up to the number of spins
N=36 and
Eg for the infinite lattice is estimated as −(1.04±0.01)
N|
J|, where |
J| is the exchange integral.
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Xiao Hu, Makoto Katori, Masuo Suzuki
1987 Volume 56 Issue 11 Pages
3865-3880
Published: November 15, 1987
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Two kinds of systematic mean-field transfer-matrix methods are formulated in the 2-dimensional Ising spin system, by introducing Weiss-like and Bethe-like approximations. All the critical exponents as well as the true critical point can be estimated in these methods following the CAM procedure. The numerical results of the above system are
Tc*\simeq2.271 (
J⁄
kB), γ=γ′\simeq1.749, β\simeq0.131 and δ\simeq15.1. The specific heat is confirmd to be continuous and to have a logarithmic divergence at the true critical point, i.e., α=α′=0. Thus, the finite-degree-of-approximation scaling ansatz is shown to be correct and very powerful in practical estimations of the critical exponents as well as the true critical point.
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H. S. Sahota, Takeki Iwashita, B. S. Grewal
1987 Volume 56 Issue 11 Pages
3881-3886
Published: November 15, 1987
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Relative K-capture probabilities in the decay of
169Yb to 472 keV, long lived 379 keV (52 nsec.), and 316 keV (660 nsec.) levels of
169Tm are measured using the technique of gamma-K X-ray sum coincidence in a single intrinsic Ge detector. The results agree with the theoretical values.
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Shigeo Imaizumi, Carl W. Garland
1987 Volume 56 Issue 11 Pages
3887-3892
Published: November 15, 1987
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The main phase transition in dipalmitoylphosphatidylcholine (DPPC) liposomes was studied with 0.03 Hz ac calorimetry. Water suspensions with 6.25 wt% DPPC and 15.0 wt% DPPC were measured with a slow temperature scanning rate of 0.12 K/h through the transition on heating and on cooling. These studies revealed a fairly narrow
Cp peak at the main transition with a hysteresis of about 0.1 K. The integrated area of the excess
Cp peak observed on heating corresponds to an enthalpy of 6 kJ/mol of DPPC in both samples. This value is much smaller than the total latent heat of 38.8 kJ/mol obtained from adiabatic calorimetry, which indicates that the rate of phase conversion is quite slow. Pretransitional fluctuation contributions to
Cp were very small both above and below the coexistence region for the main transition. No
Cp anomalies were seen at the pre- or sub-transition even at the low frequency of 0.03 Hz.
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Osamu Sano
1987 Volume 56 Issue 11 Pages
3893-3898
Published: November 15, 1987
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A theoretical study is made on the steady thermal convection of a viscous fluid confined in a vertically oriented thin toroidal loop, which is placed in vertically uniform temperature gradient. The Boussinesq approximation is employed, and first order perturbed fields from steady heat conduction state are examined. Three dimensional cellular flows are found at some critical Rayleigh numbers, which will provide a basic state to understand the bi-directional flow along the loop recently observed in our experiment.
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Hirotada Abe, Sadanojyo Nakajima
1987 Volume 56 Issue 11 Pages
3899-3910
Published: November 15, 1987
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A computational method for solving boundary-value problems for the Maxwell equation in the particle simulation is developed and is emlcodied in a code PS2M, which is a new Particle Simulation code in 2.5 dimensions (2 space-dimensions and 3 velocity-dimensions) for electroMagnetic plasmas. This method is formulated by introducing a double representation of the δ functions which are expanded by two independent sets of eigen functions in a system. The validity of solutions of the boundary-value problems is proved by invoking the mathematical law of Green’s functions. The high-order spline spatial interpolation was confirmed to be very useful in the simulation for electromagnetic plasmas, because its use removes the limit on the grid spacing, which has been severely limited of order of the Debye length in the conventional methods. This code, PS2M, has been used to study RF stabilization of the flute mode and ECRH.
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Noriyoshi Nakajima
1987 Volume 56 Issue 11 Pages
3911-3928
Published: November 15, 1987
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Analytical studies are presented on the nonlinear oscillation due to a single non-resonant current-driven mode with poloidal mode number of
m=1 in the vicinity of a marginally stable state in RFP plasmas. A perturbation expansion with respect to the difference of the toroidal wave number from one at the marginally stable state is used togather with the multiple-time-scale method. The system of equations governing the time development of the amplitude of the
m=1 mode is obtained, which indicates that the nonlinear oscillation is possible in RFP plasmas with a relatively high
S number (
S\gtrsim10
4) and that the oscillation is interpreted as an amplitude oscillation of the
m=1 mode. The analytical results by using the perturbation theory well explain those of the numerical simulation.
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Kimitaka Itoh, Sanae-Inoue Itoh
1987 Volume 56 Issue 11 Pages
3929-3933
Published: November 15, 1987
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A single-null divertor configuration in the
l=2 helical-heliotron/torsatron (
l: multipolarity of the field) is studied. The
l=1 component is introduced by placing two helical windings with a small asymmetry. This can be also realized by imposing the distributed current of coils in the poloidal direction. In this configuration, the connection length of the field line outside of the separatrix becomes longer, and the access of the heating (such as ICRF wave) from the low-field side is possible.
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Shin’ichi Takeda, Shuzi Harada, Shigeru Tamaki, Eiichiro Matsuba ...
1987 Volume 56 Issue 11 Pages
3934-3940
Published: November 15, 1987
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Neutron diffraction measurements of liquid Na–Pb alloys have been carried out to reveal the short range order in the liquid state. In the Na-rich region, an additional small peak has been clearly observed in the low
Q side of the main peak of the structure factors and this implies the formation of a local atomic association like molecular cluster such as Na
4Pb in this alloy system. The structure factor of this system was calculated by the formula of three component hard-sphere system, assuming to be a mixture of Na, Pb and Na
4Pb. The calculated total structure factors appear to agree well with the observed ones.
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Takeshi Moriya, Taira Suzuki
1987 Volume 56 Issue 11 Pages
3941-3950
Published: November 15, 1987
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A statistical dislocation model is proposed of the anomalous temperature dependences of flow stress below about 50 K found in many alloys. A thermal unit process is assumed to consist of a triggering thermal unpinning of an obstacle and mechanical unzippings following it. The dimensions of the unit vary with temperature and stress. A selfconsistency condition on fluctuation and relaxation of the distribution of dislocation configurations is taken into account. The model can explain the experiments well without detailed assumptions. The anomalies are found to occur, due to the onset of cooperative two dimensional propagations of unzipping motion of dislocations assisted by inertial effects.
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G. Soda, C. Bourbonnais, D. Jerome
1987 Volume 56 Issue 11 Pages
3951-3955
Published: November 15, 1987
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The spin-lattice relaxation
T1 of
14N(
I=1) nuclei in a single crystal of the mixed-valency platino-cyanate K
2Pt(CN)
4Br
0.33.2H
2O(KCP) quasi-one dimensional conductor has been measured in the temperature domain from room temperature down to the 3-D Peierls ordering below 120 K. A rapid increase of the quadrupolar relaxation is observed below 220 K which follows the power law 1⁄
T1α
r−1⁄2 where
r=(
T−
Tp)⁄
Tp. This behaviour is explained in terms of the critical slowing down of lattice fluctuations with a Landau-Ginzburg theory. The square root critical divergence of
T1−1 is the signature of the harmonic regime for the order parameter fluctuations. The enhancement of
T1−1 and the very wide 3-D critical width can be explained by the strong anisotropy of correlation lengths in this Q-1-D conductor.
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Naoyuki Sasaki, Takeshi Kambara
1987 Volume 56 Issue 11 Pages
3956-3960
Published: November 15, 1987
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Hendrickson
et al. (Inorg. Chem.
20 (1981) 131) showed that the transition temperature for the (
Remark: Graphics omitted.) transition in the spin crossover compound [Fe
xCr
1−x(3-OCH
3-SalEen)
2]PF
6 decreases with increasing the Cr concentration, whereas the transition temperature in [Fe
xCo
1−x(3-OCH
3-SalEen)
2]PF
6 increases with increasing Co concentration. These dilution effects on the (
Remark: Graphics omitted.) transitions is studied on the basis of the ligand field theory by taking account of the coupling between d electrons of iron and a lattice strain. The present model clarifies the origins of the two kinds of dilution effects. In the latter case, the lattice contraction is induced by the Co ions. The effect of the contraction of the transition is reasonably treated as the pressure effect. The calculated temperature dependence of the effective magnetic moment for various dopant concentrations reproduces the essential features of the two types of observed results.
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Akihiko Matsuyama, Fumihiko Tanaka
1987 Volume 56 Issue 11 Pages
3961-3969
Published: November 15, 1987
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The present paper analyzes theoretically a first-order transition from partial to perfect wetting of a wall by demixed polymer solutions. On the basis of Cahn’s construction for the free energy, we evaluate the interfacial tension, adsorption amounts and the contact angle as a function of χ−χ
c, chain length and the adsorption energy parameter ε, where χ
c is the value of the Flory-Huggins parameter χ at the critical point. It is shown that a value χ
w exists, where a transition from partial to perfect wetting occurs. The capital region χ
c<χ<χ
w(χ
w<χ) corresponds to perfect (partial) wetting state. The perfect-wetting region becoms larger as the molecular weight of the polymer increases. The wetting transition in polymer blends, i.e., mixed chains of different length, is also studied.
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Kaoru Iwano, Yasushi Wada
1987 Volume 56 Issue 11 Pages
3970-3982
Published: November 15, 1987
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Eilenberger formalism for superconductivity is applied to conducting polymers. It reproduces the known structures of soliton and polaron, in a straightforward way, for a Peierls chain system in which the half of electron levels are occupied. The continuum model for polyacetylene, by Takayama, Lin-Liu, and Maki, is used. It is, then, applied for the one-third filled case of a Peierls-Froehlich system. For a particular value of coupling strength, we find self-consistent soliton solutions with fractional charges ±2
e⁄3. It turns out to be the single soliton limit of the Fischbeck soliton lattice. It is shown that there are no corresponding solutions in the one third filled case of the continuum limit of the Su, Schrieffer, and Heeger model.
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Yuri Nakao, Shinya Wakoh
1987 Volume 56 Issue 11 Pages
3983-3989
Published: November 15, 1987
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In this paper, we report the results of the ATA calculations of the band structures and the Fermi surface of V
1−xMo
x(
x=0.8, 0.5 and 0.2), Cr
0.5Mo
0.5 and V
0.5Nb
0.5. In order to test the reliability of the ATA framework, the complex energy bands and the electronic density of states in V
0.5Mo
0.5 and Nb
0.5Mo
0.5 are calculated by the CPA. Any marked difference between the ATA and the CPA results are not found for these systems.
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Akira Hasegawa, Akira Yanase
1987 Volume 56 Issue 11 Pages
3990-3996
Published: November 15, 1987
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To investigate an origin of the anomalously large residual resistivity in CePd
3, a typical intermediate-valence compound, the energy band structure is calculated by a full-potential linear APW method and a relativistic APW method with the density-functional theory in a local-density approximation. Calculations show that small Fermi surfaces may exist in the 4f bands and play an essential role in the electrical conduction. In the alloy system in which Ce is replaced with La, the electron scattering by the La impurity seems to occur in the unitarity limit. The sharp rise of the resistivity observed by the replacement of Pd with Ag or Cu is ascribed to the Anderson localisation in the 4f bands.
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Hal Bon Gu, Tohru Takiguchi, Shigenori Hayashi, Keiichi Kaneto, Katsum ...
1987 Volume 56 Issue 11 Pages
3997-4002
Published: November 15, 1987
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Effects of ammonia gas on the electrical conductivity, photoluminescence, optical absorption and electron spin resonance of poly (p-phenylene vinylene) (PPV) have been studied. The electrical conductivity and luminescence intensity in PPV have been found to increase upon exposure to ammonia gas in contrast to the well-known compensation effect of ammonia gas on other conducting polymers. The results are discussed in comparison with the data of lightly doped samples with p-type dopant (ClO
4−) and n-type dopant (TBA
+).
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Masumi Takeshima
1987 Volume 56 Issue 11 Pages
4003-4014
Published: November 15, 1987
Released on J-STAGE: June 01, 2007
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The previously developed theories of the impurity-doping effect on electronic states in quasi-two and quansi-one dimensional structure semiconductors are extended to take into account the Coulomb-hole term in the exchange interaction. The theory is applied to single-quantum-well and single-quantum-wire of n-type GaAs embedded in undoped GaAlAs, considering the conduction band. The effect of the Coulomb-hole term is to partially cancel the shift of the density of states (DOS) toward higher energy produced by the multi-site multiple impurity-scatterings. It is shown that the Coulomb-hole term effect in lower-dimension structures is as important as that in a three-dimensional structure.
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Toyohiko Kinoshita, Hiroshi Ohta, Yoshiharu Enta, Yukou Yaegashi, Shoj ...
1987 Volume 56 Issue 11 Pages
4015-4021
Published: November 15, 1987
Released on J-STAGE: May 29, 2007
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Momentum-resolved inverse photoemission spectra have been measured for Si(111) \sqrt3×\sqrt3-Sn and -In surfaces. An empty part of the metallic surface-state band for \sqrt3×\sqrt3-Sn is observed. It is noted that the metallic band (including the empty and filled parts) for the \sqrt3×\sqrt3-Sn surface disperses in the same manner as the empty band for the \sqrt3×\sqrt3-In surface. This is consistent with the previous proposal that the atomic arrangements of the \sqrt3×\sqrt3-Sn and \sqrt3×\sqrt3-column III surfaces are identical to each other. For the Si(111)2\sqrt3×2\sqrt3-Sn surface, momentum-resolved inverse photoemission spectra and coverage-dependent angle-resolved photoemission spectra have been measured. It has been found that the 2\sqrt3×2\sqrt3-Sn surface is semiconducting and at least two filled- and one empty-surface-state bands exist in the bulk band gap.
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Shigeki Kojima, Takamitsu Kobayashi, Kiyomi Okamoto, Mieko Ohtsuka
1987 Volume 56 Issue 11 Pages
4022-4026
Published: November 15, 1987
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Fluctuation-induced conductivity (FIC) above the superconducting transition temperature was investigated for aluminum films with respect to the effect of gold overdeposition. Thicknesses of gold were 0, 1/2, 1 and 3/2 atomic layer. The measured FIC was well explained by the traditional superconducting fluctuation theory. The values of the pair-breaking parameter δ increased with the increase of gold thickness. An experimental relation between the pair-breaking parameter δ and the normal sheet resistance (
Remark: Graphics omitted.), (
Remark: Graphics omitted.), holds for the samples with 1 atomic layer of gold as for the unoverdeposited samples. The constant term
a for the overdeposited samples is, however, larger than that for the unoverdeposited samples. This is considered to be due to the spin-orbit scattering effect owing to the existence of gold.
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Hiroaki Kadowaki, Koji Ubukoshi, Kinshiro Hirakawa, José L. Mar ...
1987 Volume 56 Issue 11 Pages
4027-4039
Published: November 15, 1987
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Critical properties of a Heisenberg antiferromagnet on a triangular lattice are investigated experimentally using a quasi-two-dimensional antiferromagnet VCl
2 by means of neutron scattering. It is found that VCl
2 shows characteristic critical behaviors of two and three dimensional models. A little above
TN, the line shape of χ(
Q) is found to be represented by the Ornstein-Zernike form (κ
2+
q2)
−1. This suggests the existence of magnetic point defects which were predicted in the two dimensional model. The measured critical exponents are β=0.20±0.02, γ=1.05±0.03, and ν=0.62±0.05, in agreement with the theoretical work for three dimensional SO(3) systems. Successive phase transitions due to a small Ising anisotropy were found at
TN1=35.88±0.01 K and
TN2=35.80±0.01 K. The spin structure and the dispersion relation of the spin wave well below
TN are also determined.
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Masayuki Shiga, Yoji Nakamura
1987 Volume 56 Issue 11 Pages
4040-4046
Published: November 15, 1987
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Magnetic properties of stoichiometric and off-stoichiometric NbFe
2 intermetallic compounds have been studied. It has been revealed that the stoichiometric NbFe
2 shows strongly enhanced Pauli paramagnetic properties. The temperature dependence of its susceptibility in a weak external field shows a maximum as observed in other exchange enhanced metals such as TiBe
2. The concentration deviations from the stoichiometry toward both sides result in ferromagnetism. The origins of the ferromagnetism in off-stoichiometric compositions are discussed.
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Takejiro Kaneko, Takeshi Kanomata, Kiwamu Shirakawa
1987 Volume 56 Issue 11 Pages
4047-4055
Published: November 15, 1987
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The pressure effect on the magnetic transition temperatures of Mn
3GaC, Mn
3ZnC and Mn
3SnC were measured under pressures up to 13 kbar. The pressure derivatives of the transition temperatures are obtained to be d
Tt⁄d
P=−3.5 K/kbar and d
TC⁄d
P=0.4 K/kbar for Mn
3GaC, d
Tt⁄d
P=−0.9 K/kbar and
TC⁄d
P=0 for Mn
3ZnC and d
TC⁄d
P=−1.9 K/kbar for Mn
3SnC, where
Tt and
TC are the magnetic order-order transition temperature and the Curie temperature, respectively. An intermediate magnetic phase (I) is induced in Mn
3GaC under pressures above 3 kbar. The triple point (Antiferro./I/Ferro.) was determined to be
Tc=158 K and
Pc=3 kbar. The temperature variations of magnetization, magnetic susceptibility and lattice parameter were also measured.
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Ikuo Nakai, Osamu Yamada, Masanao Mimura, Shunji Ishio, Minoru Takahas ...
1987 Volume 56 Issue 11 Pages
4056-4063
Published: November 15, 1987
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We have carried out precise measurements of the magnetization on an amorphous metallic ferromagnet Fe
83B
17 from 4.2 K to 340 K in a high field of 5.03 T. Detailed analysis of the observed data shows that the magnetization does not obey a simple spin wave
T3⁄2 law but follows a sum of the renormalized spin wave term and the Stoner-type contribution varying as
T2 rather than e
−Δ⁄kBT. The spin wave stiffness constant is expressed as
D=
D0(1−
D2T5⁄2) with
D0=120±5 meV Å
2 and
D2=(2.0±0.5)×10
−8 K
−5⁄2, which is roughly consistent with that determined directly from neutron scattering. This suggests no existence of the well-known anomaly of the spin wave stiffness constant reported in earlier measurements. We discuss behavior of the magnetization at finite temperatures in terms of the local magnetic moment.
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Makio Kurisu
1987 Volume 56 Issue 11 Pages
4064-4074
Published: November 15, 1987
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Pressure-induced structural transitions and associated changes in magnetism of the light RAg have been thoroughly investigated from measurements of electrical resistivity ρ, ac magnetic susceptibility up to 37 kbar, magnetization σ up to 15 kbar and compressibility up to 3 kbar in temperatures from 1.5 K to 300 K. A cubic to tetragonal structural transition
TM is found to be induced at pressure
pc=6, 2, 10 and 30 kbar for R=La, Ce, Pr and Nd, respectively, and to increase with further increasing
p at about the same rate of +13∼+16 K/kbar. The appearance of
TM and the different
pc values for the RAg are discussed on the basis of the band Jahn-Teller model.
TM is accompanied by a shift of the magnetic ordering temperature
Tmag. For CeAg, another structural transition
TM is also found at
p=20 kbar. The remarkably larger pressure effects of
Tmag, ρ and σ are briefly discussed with recent theories of the Kondo lattice.
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Yoshikazu Andoh
1987 Volume 56 Issue 11 Pages
4075-4086
Published: November 15, 1987
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Magnetic studies have been performed on single crystals of the C-14 type Laves phase RRu
2 (R=Gd, Tb, Dy, Ho and Er) and the pseudo-binary (R
1−xY
x)Ru
2 (R=Tb, Dy, Ho and Er) compounds in the temperature range from 4.2 K to 300 K. DyRu
2 shows a transition from cone structure to ferromagnetic one at 15 K and the other RRu
2 compounds exhibit ferromagnetism. The magnetization curves of the RRu
2 single crystals show their own characteristic behaviors dependent on the sort of R atoms. Lower moments for all RRu
2 compounds except GdRu
2 are observed at 4.2 K. The results are interpreted in terms of the single ion Hamiltonian including applied field, molecular field and crystal electric field (CEF) terms. From the analysis, the
Bnm(
n≥4) terms were found to be dominant in this system. Tlne bi-quadratic exchange interaction seems to contribute to magnetic properties in TbRu
2 and DyRu
2.
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Fumitaka Matsubara, Sakari Inawashiro
1987 Volume 56 Issue 11 Pages
4087-4101
Published: November 15, 1987
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Spin structures of quasi-two-dimensional isotropic and anisotropic antiferromagnetic Heisenberg models on a hexagonal close-packed (hcp) lattice are analyzed by using a mean field theory and studied by using a Monte Carlo method. In anisotropic and an xy-like models, an incommensurate (IC) phase occurs at low temperatures and a phase transition between the IC phase and the paramagnetic phase is of the first order. In an Ising-like model, a special paramagnetic phase occurs at intermediate temperatures where an IC short range order develops much. As the temperature is decreased, an IC long range order occurs when the anisotropy is small, whereas a non-periodic frozen phase occurs when the anisotropy is large. Comments on recent experiments on LiNiO
2 and NaTiO
2 are given.
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Hatsuo Tange, Kazunori Inoue, Tatsuo Kamimori, Mitita Goto
1987 Volume 56 Issue 11 Pages
4102-4106
Published: November 15, 1987
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Pressure effects on magnetic moment μ and Curie temperature
Tc have been estimated indirectly from forced volume magnetostriction dω⁄d
H measured by 3-terminal capacitance method instead of strain gauge technique for Ni–Tm [Tm=Ti, V, Cr, Mn] alloys. The relation between pressure coefficients, d ln μ⁄d
p and d ln
Tc⁄d
p, are analyzed according to Inoue-Shimizu discussion. The values of the coefficient
C⁄χ
hfTc obtained seem to decrease gradually to about 1 in the limit of weak itinerant ferromagnet with decreasing
Tc toward 0 K for Ni–Tm [Tm=Ti, V, Cr] alloys except for Ni–Mn alloys.
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Nobuyoshi Yamada, Satoru Funahashi, Fujio Izumi, Mineaki Ikegame, Tetu ...
1987 Volume 56 Issue 11 Pages
4107-4112
Published: November 15, 1987
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The magnetic structure of an N-type ferrimagnet κ-Mn
5Ge
2 has been determined by Rietveld analysis of its powder neutron diffraction data. The magnetic moments on three Mn sites (4
b, 8
f, 8
j) has been found to be collinear along an orthorhombic
b axis, with the respective values μ(4
b)=2.54±0.11 μ
B, μ(8
f)=2.26±0.06 μ
B. and μ(8
j)=−3.11±0.08 μ
B, at 13 K.
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Tadashi Shimizu, Hiroshi Yasuoka, Z. Fisk, J. L. Smith
1987 Volume 56 Issue 11 Pages
4113-4125
Published: November 15, 1987
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The temperature dependences of susceptibility and
63Cu Knight shift in YbCu
2Si
2 single crystal have been measured for the fields parallel and perpendicular to the
c-axis in the temperature range between 4.2 K and 300 K. The anisotropy of the susceptibility was found to be quite increased with decreasing temperature between 20 K and 200 K, suggesting that the crystalline electric field (CEF) effect is important in YbCu
2Si
2. It was also observed that the linear relation between the Knight shift and the susceptibility is broken around 100 K for both the directions, and that the hyperfine coupling is highly anisotropic even at higher temperatures. The origins of the non-linearity and the anisotropy of the hyperfine coupling has been attributed to a nature of the orbitally dependent exchange interaction between 4f and conduction electrons.
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