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Takashi Yabe, Pei-Yuan Wang
1991 Volume 60 Issue 7 Pages
2105-2108
Published: July 15, 1991
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A unified numerical procedure is proposed as a solver both for compressible and incompressible fluids. The method approaches the MAC algorithm at very high sound speed and continuously approaches the algorithm for compressible fluid with decreasing sound speed. The advection term is treated by the CIP algorithm which was previously proposed and gives quite accurate and less-diffusive results. This unified procedure is tested both by one-dimensional shock-tube problem and two-dimensional cavity flow at high-Reynolds number.
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Mitsugu Matsushita, Shunji Ouchi, Katsuya Honda
1991 Volume 60 Issue 7 Pages
2109-2112
Published: July 15, 1991
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Contour lines of a self-affine surface with a specified value of Hurst exponent
H show certain special characteristics in fractal structure and statistics. The first argument is that the fractal dimension
De of an entire pattern formed by contour lines of the same altitude, similar to coastlines, should be distinguished from the fractal dimension
Dc of single contour lines. It is then confirmed that
De=2−
H. The exponent ζ characterizing a power-law form of the size distribution of closed contour lines, similar to islands, is found to be equal to
De. Self-avoiding fractional Brownian motion is newly introduced to derive a new scaling law
Dc=2⁄(1+
H).
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A. Hamid Bougourzi, Yukio Kikuchi, Wataru Ishizuka
1991 Volume 60 Issue 7 Pages
2113-2117
Published: July 15, 1991
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It is known that free-field realization of Kac-Moody algebra is not unique. By taking the explicit example of one parameter extension of
SU(3), that is, the generalization of the well-known Wakimoto representation, we make some remarks on the relation between Kac-Moody currents and screening currents. Corresponding
SU(3) parafermions are also considered. A general procedure is outlined to obtain the general parameter extension of the Wakimoto representation of KM algebras with free fields.
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Yousuke Watanabe, Takahiko Sasaki, Hideki Sato, Naoki Toyota
1991 Volume 60 Issue 7 Pages
2118-2121
Published: July 15, 1991
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From low-temperature X-ray diffraction measurements, the interlayer spacing
d100 of the layered organic superconductor κ-(BEDT–TTF)
2Cu(NCS)
2 is revealed to take a maximum around 100 K. Since
d100=
a·sin β (
a is the monoclinic lattice parameter and β the angle between the
a- and
c-axes), this anomalous maximum is due to the combined effect of the monotonous increasing
a and decreasing sin β (β>90°) with decreasing temperatures. This result can be attributed to the structural changes in the hydrogen bonding between the terminal ethylene CH
2 and the counter anion molecule –SCN–Cu–NCS–.
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Yoshio Kitaoka, Hiroyuki Nakamura, Taisuke Iwai, Kunisuke Asayama, Udo ...
1991 Volume 60 Issue 7 Pages
2122-2126
Published: July 15, 1991
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The magnetic and superconducting phase diagram of Th-doped Ce
1−xTh
xCu
2.2Si
2 has been established by Cu NMR and NQR technique and is compared with that of CeCu
2.02Si
2. Static magnetic ordering with
TN=2.4 K and 4.5 K for
x=0.08 and 0.12, respectively, is evidenced by a pronounced broadening of the
63Cu-NQR and -NMR spectra and a pronounced anomaly in the specific heat. In contrast, for the lightly Th-doped compounds with
x≤0.064, there has been observed neither a signature of a broadening of the NQR and NMR spectra nor an anomaly of the specific heat, but a dramatic reduction of the NMR and NQR intensities below a temperature ranging from 0.9 K to 1.3 K upon increasing Th-content. It is emphasized that the unusual “
magnetic transition” found in undoped and lightly Th-doped CeCu
2.2Si
2 should be distinguished from the static magnetic ordering in the heavily Th-doped systems.
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Yoshichika \={O}nuki, Sung Won Yun, Isamu Ukon, Izuru Umehara, Kazuhik ...
1991 Volume 60 Issue 7 Pages
2127-2130
Published: July 15, 1991
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We have measured the magnetoresistance and de Haas-van Alphen (dHvA) effect in the ferromagnetic compound UGe
2. It is found that UGe
2 is a compensated metal whose Fermi surface supports open orbits, along the
b- and
c-axes of the orthorhombic crystal structure. From the dHvA experiment, we have detected carriers with heavy cyclotron masses, ranging from 2.3
m0 to 24.5
m0.
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Nobumori Kinoshita, Madoka Tokumoto, Hiroyuki Anzai
1991 Volume 60 Issue 7 Pages
2131-2134
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An anomalous behavior was found in the temperature dependence of the ESR spectrum and the electric resistance of (BEDT–TTF)
2RbHg(SCN)
4 below 20 K. The anomaly was compared with that of the isostructural salt [(BEDT–TTF)
2KHg(SCN)
4] and based on the similarity of the anomaly between the Rb and the K salts, the possibility of the coexistence of a metallic state with a magnetic ordered state at low temperatures was pointed out.
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Marcel Miglierini, Saburo Nasu
1991 Volume 60 Issue 7 Pages
2135-2138
Published: July 15, 1991
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Changes in the shapes of the
57Fe Mössbauer spectra of an Al
40Cu
7Ge
25Mn
25Fe
3 icosahedral quasicrystal have been found from low temperature measurements. The results obtained are interpreted in terms of a possible magnetic transition at 30 K.
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Yutaka Iwata, Iwao Shibuya, Yoshihiro Ishibashi
1991 Volume 60 Issue 7 Pages
2139-2142
Published: July 15, 1991
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The crystal structure of the low-temperature phase (γ-phase) of the dipolar frustrated crystal K
2Ba(NO
2)
4 was determined at −120°C by X-ray measurement of superlattice reflections. A superlattice model proposed for the γ-phase has been refined. The space group is reasonably assigned as monoclinic
C2⁄
m-
C2h3, and the configurations of all the NO
2 groups are found to be ordered. The symmetry agrees with the theoretical prediction made by Ishibashi
et al., implying that the γ-phase is ferroelastic.
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Ping He, Kiyoshi Deguchi, Eiji Nakamura
1991 Volume 60 Issue 7 Pages
2143-2146
Published: July 15, 1991
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Elastic stiffness constants
s66E and
s66D of Rb
1−x[N(H
1−yD
y)
4]
x(H
1−yD
y)
2PO
4 (
x=0.5;
y=0, 0,5, 0.7, 1.0) were determined between 4.2 K and 350 K. Pronounced effects of deuteration were found in the temperature dependences of
s66E and
s66D. Deviation from the elastic Curie-Weiss law of (
s66E−
s66D)
−1 vs temperature was found below the onset temperature
Tm, as in the case of the dielectric one. The temperature
Tm increases with the increase of deuteration rate from 120 K (
y=0) to 220 K (
y=1.0). Unlike the case of the pure crystals of the KDP family, a slight anomaly of
s66D was observed between
Tm and the Vogel-Fulcher temperature
T0.
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Yoshio Kamishina, Yukikuni Akishige, Masao Hashimoto
1991 Volume 60 Issue 7 Pages
2147-2150
Published: July 15, 1991
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Dielectric constants and
D-
E hysteresis loops have been measured on trichloroacetamide (TCAA) single crystals. Only along the crystallographic
b-axis are remarkable dielectric anomalies found at
TC=354.6 K and
TI=356.9 K upon heating. The Curie-Weiss relation holds in the high-temperature phase with a very small Curie constant of about 5.6 K. Typical ferroelectric
D-
E hysteresis loops are observed only in a limited temperature range of a few degrees just below
TC; the spontaneous polarization
Ps and the coercive field
Ec are estimated to be about 0.2 μC/cm
2 and 4 kV/cm, respectively, at 350 K. Since the
Ec steeply increases with decreasing temperature, it is difficult to reverse the
Ps at room temperature. Some discussions are presented for the causes of the weak ferroelectricity on TCAA.
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Masao Nomura
1991 Volume 60 Issue 7 Pages
2151-2158
Published: July 15, 1991
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Caselle-Ponzano fusion rules, based on graph theory, are investigated in the framework of Wigner-Racah algebras. While in the graph theory parameters of fusion rules are taken over specific values, the restriction of parameters is removed in the present formalism. Formal extension to
q-analogs is also given.
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Yuji Nakawaki
1991 Volume 60 Issue 7 Pages
2159-2174
Published: July 15, 1991
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We consider the nonlinear Schrödinger model of spin-1/2 particles with attractive coupling to show a way to complete an infinite volume formulation of the quantum inverse scattering method. We use not any lattice models but only properties of the Jost functions satisfying given asymptotic boundary conditions in infinities. We find orthonormality relations of scattering data operators as well as underlying ones of the Jost functions and use them to derive operator identities satisfied by inverse operators of scattering data operators. Consequently we can simplyfy constructing the Gel’fand-Levitan equations. We also realize scattering data operators in terms of reflection coefficient operators.
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Nicolo’ Arena, Sebastiano Cavallaro, Alberto D’Arrigo, Gio ...
1991 Volume 60 Issue 7 Pages
2175-2178
Published: July 15, 1991
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An appropriate choice of the beam energy and detector geometry allowed us to observe the
8Be excitation energy region around 20 MeV by the
7Li(
d, αα)
n reaction. The analysis of the αα bidimensional spectra coming from this reaction at 7 MeV deuteron incident energy shows the contributions of the
8Be levels which in the above energy region decay also in two α particles. The width Γ of the
Jπ=2
+ and 0
+,
T=0
8Be states at
Ex=20.1 and 20.2 MeV, respectively, has been deduced.
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Isamu Nakata
1991 Volume 60 Issue 7 Pages
2179-2183
Published: July 15, 1991
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Nonlinear electromagnetic waves in a ferromagnet under an external magnetic field are investigated in the presence of dissipative effect by using a nonlinear perturbation method. In the lowest order of perturbation, it is found that the system of equations for the electromagnetic waves in a ferromagnet can the reduced to an integro-differential equation. It is shown that this equation admits steady state solutions representing either monotone or oscillatory shock waves according to the relative strength of the dissipation to the dispersion.
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Shigeo Kida, Masanori Takaoka
1991 Volume 60 Issue 7 Pages
2184-2196
Published: July 15, 1991
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The perpendicular components to vorticity of the Laplacian of vorticity multiplied by the kinematic viscosity, ν(∇
2ω)
⊥, represents the rate of breakdown due to viscous effects of the frozen motion of vortex lines with fluid particles, whereas the parallel component, ν(∇
2ω)
⁄⁄, represents the deviation of the stretching rates of vortex and fluid line elements. The spatial distributions of high-value regions of these two components and vorticity are compared in detail in several analytical and numerical flows. It is found that ν(∇
2ω)
⁄⁄ takes large negative values typically inside high-vorticity regions. On the other hand, ν|(∇
2ω)
⊥| is large where the high-vorticity regions are interacting, which suggests that ν(∇
2ω)
⊥ may serve as a good measure of the degree of vorticity reconnection.
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Tatsuo Watanabe, Chihiro Matsuoka, Nobuo Yajima
1991 Volume 60 Issue 7 Pages
2197-2200
Published: July 15, 1991
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Theoretical analysis is given on the reflection and transmission of a planar ion-acoustic soliton incident obliquely on a plasma sheath formed at both sides of a negatively biased metal mesh. Snell’s law is shown to hold for solitons propagating through the sheath.
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Yoshiomi Kondoh, Nobunao Takeuchi, Akio Matsuoka, Yasuyuki Yagi, Youic ...
1991 Volume 60 Issue 7 Pages
2201-2209
Published: July 15, 1991
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The effect of the pressure on the mode transition point of the relaxed state from the cylindrical state to the mixed helical one is investigated, by using the associated eigenvalue problem derived from the reminimization of the energy integral for the nonideal MHD plasma. The eigenvalue which gives the mode transition point is solved to the 1st order approximation by the perturbation method. Numerical results by the eigenvalue show that the pressure effect leads to fairly large shifts of the mode transition points and makes them closer to the experimental operating region reported so far. Comparison between the theoretical and the experimental data shows that the experimental data tend to evolve along the line of constant β
ax.
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Yoshinosuke Terashima
1991 Volume 60 Issue 7 Pages
2210-2217
Published: July 15, 1991
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Particle trajectories in the wave frame are expressed in an integral form which elucidates the roles of the applied electrostatic wave field and of the induced
Vp×
B field. Both the non-relativistic and relativistic cases are treated. In each case, the energy integral is shown to exist and a criterion for transition from trapping to detrapping is obtained, and thereby the optimum value of energy gain is deduced. It is shown that, when the
E×
B velocity, υ
E, due to the wave field in the wave frame is less than the light speed, the Lorents factor of an accelerated particle, γ(υ), is almost limited by γ
c=(1−υ
E2⁄
c2)
−1⁄2, while for υ
E>
c, γ(υ) possibly increases linearly with time.
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Seiji Ishiguro, Noriyoshi Sato
1991 Volume 60 Issue 7 Pages
2218-2228
Published: July 15, 1991
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Potential formation due to contact between a floated emissive plane electrode and collisionless plasma is investigated by means of particle simulations. When low-temperature high-density thermal electrons are emitted, a negative potential dip is created in front of the electrode. With an increase in the emission flux from the electrode, the electrode potential increases and finally becomes larger than the plasma potential. When a high-density electron beam is injected from the floated electrode, there appears a stationary electron sheath in front of the electrode, which reflects most of the injected electrons. This sheath also reflects ions flowing from the plasma toward the electrode. When the beam density is low, such an electron sheath is not created. An intermediate-density beam injection gives rise to a recurrence phenomenon and the electron sheath structure appears periodically in time.
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Yoshinori Katayama, Kenji Maruyama, Makoto Yao, Hirohisa Endo
1991 Volume 60 Issue 7 Pages
2229-2240
Published: July 15, 1991
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EXAFS, PAS and ESR measurements have been carried out on the Se–S mixed chains isolated in the channels of mordenite crystal. In the isolated Se
1−xS
x mixed chains the Se–Se and S–S like-pairs are somewhat preferable to the Se–S unlike-pairs. The photo-induced absorption bands appear in the mixed chains at low temperatures, which are accompanied by ESR signal. The induced ESR signal contains a strongly anisotropic component with average
g-value higher than 2. The anisotropic component can be assigned to the neutral dangling-bond defect C
10.
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Shin’ichi Takeda, Shuzi Harada, Shigeru Tamaki, Yoshio Waseda
1991 Volume 60 Issue 7 Pages
2241-2247
Published: July 15, 1991
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The structure factor of liquid aluminum at 670°C has been newly determined by neutron diffraction with sufficient accuracy and compared with the structural data obtained by X-ray diffraction. A remarkable difference in these two structural informations is clearly detected and it is apparently larger than the experimental uncertainties. The ion-electron correlation function in liquid aluminum has been estimated from this difference with the help of theoretical values of the electron-electron correlation function by the Utsumi-Ichimaru scheme, and the valence electron charge distribution around an ion in liquid aluminum was obtained. The present result is found to agree well with the distribution function of valence electrons in solid aluminum using the pseudopotential method and suggests that the valence electrons in liquid aluminum would most likely behave as nearly free, although there is a minor mixing with the atomic wave function at the close vicinity of the ionic radius, corresponding to the orthogonalised plane wave.
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Norikazu Ishimura, Takao Yamamoto
1991 Volume 60 Issue 7 Pages
2248-2255
Published: July 15, 1991
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We introduce a new one-dimensional competitive system constructed of particles with Ising spin variables in a periodic substrate potentials, a hard-core type inter-particle interaction and a spin-spin interaction whose exchange energy depends linearly on the distance between adjacent particles. The hard-core interaction mediates an antiferromagnetic spin-spin interaction. Although the range of the inter-particle interaction is finite, long-period commensurate phases are caused. Many commensurate phases appear in the ground state phase diagram.
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Masayuki Hasegawa, Takeshi Inaoka, Toshihiro Ichikawa
1991 Volume 60 Issue 7 Pages
2256-2268
Published: July 15, 1991
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We propose a theory of multiple scattering in the reflection high-energy electron diffraction (RHEED) intensities from liquid metal surfaces and apply it to liquid In, for which preliminary RHEED experiments have recently been performed. In this theory, we first calculate the RHEED specular reflectivity based on an effective refractive index model, in which external electrons are supposed to be reflected by a smoothed surface potential. Multiple scattering effect is taken into account in terms of the damping factor of the refracted and specularly reflected waves calculated in this model. Specular reflectivity is then calculated using this damping factor together with an appropriately defined local reflectivity. Application of this theory to liquid In shows that multiple scattering effect is not very appreciable in the range of small glancing angles, where preliminary RHEED data are available.
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Dai S. Hirashima, Yoshiaki \={O}no, Kazuo Miura, Tamifusa Matsuura, Hi ...
1991 Volume 60 Issue 7 Pages
2269-2284
Published: July 15, 1991
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Electronic states in the
d-
p model, particularly those around the half-filled case, are investigated with the help of the auxiliary boson method and the 1⁄
N-expansion. The critical value of the charge transfer energy for a metal-insulator transition to occur at the half-filled case is evaluated. The analytic expression for the charge susceptibility is given. Then characteristics of the charge fluctuation around the transition point are clarified; it is found that the charge susceptibility vanishes on the critical point. Furthermore, dependence of the charge susceptibility on the hole number and on the charge transfer energy is studied. Relevance to high temperature superconducting materials is then discussed.
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Katsuhiko Takegahara, Tadao Kasuya
1991 Volume 60 Issue 7 Pages
2285-2294
Published: July 15, 1991
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The APW band calculations for LaThCuO
4 with Nd
2CuO
4 type crystal structure were performed with two kinds of structure for the La and Th layers. It was shown that, as the Th doping increases in La
2CuO
4, the Cu
d-O
p antibonding band on the CuO
2 layer rises steadily but the La–Th
d(
xy) band falls sharply with the bottom at the X point. In LaThCuO
4, the bottom of
d(
xy) band is well below the top of the antibonding band as well as the Fermi energy. Various experimental results in the Th or Ce doped Nd
2CuO
4 are explained by the present result.
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Masaki Goda, Hiroaki Yamada, Yoji Aizawa, Kaoru Kurumi, Akira Shudo, H ...
1991 Volume 60 Issue 7 Pages
2295-2304
Published: July 15, 1991
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Spectral property and Lyapunov exponent of electronic wave function (
L-exponent) in a modified Bernoulli system with inverse-power-law structural correlation, is studied in detail numerically and theoretically. By changing the value of the bifurcation parameter
B specifying a strength of the correlation in the interval (1, ∞), two transitions (a transition around
B=3⁄2 and another one at
B=2) appear. For the case 3⁄2≤
B<2 of long-range structural correlation, two peaks appear and compete in the distribution function of
L-exponent of finite system and the distribution does not obey the central-limit theorem. At the critical point
B=2 (and also for
B>2),
L-exponent in infinite system vanishes with probability 1.
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Shintaro Nakamura, Terutaka Goto, Yosikazu Isikawa, Shinichi Sakatsume ...
1991 Volume 60 Issue 7 Pages
2305-2310
Published: July 15, 1991
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Elastic properties of the dense Kondo compounds CeNiSn and CePdSn with orthorhombic structure have been investigated by the ultrasonic measurements. The anomalous softening of the longitudinal C
11, C
22 and C
33 modes in CeNiSn is responsible for the energy gap at the Fermi level in the quasiparticle band. A remarkable anisotropic behavior on the resistivity as well as the elastic constant in the magnetic field along the crystallographic
a,
b,
c-axes has been observed. In CePdSn, the softening in the longitudinal C
22 and C
33 modes has been found.
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Mikio Eto, Hiroshi Kamimura
1991 Volume 60 Issue 7 Pages
2311-2323
Published: July 15, 1991
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Electronic structures of La–Sr–Cu–O and Nd–Ce–Cu–O compounds are investigated from first principles, taking CuO
6, CuO
4, Cu
2O
11 and Cu
2O
7 clusters, as a model. Many-body states are calculated in the presence of the correlation effect by the MCSCF-CI variational method. In the hole-doped CuO
6 cluster we have shown that the ground state changes from
1A
1g to
3B
1g near the doping concentration of the onset of superconductivity, owing to the effect of the apical oxygens. While in the electron-doped CuO
4 cluster the ground state is always
3B
1g, in which the dopant electron is accommodated in the Cu 4s orbital. The effects of the doped ions are also discussed. In the undoped Cu
2O
11 and Cu
2O
7 clusters two electrons are localized at Cu sites, reflecting the strong correlation effect, and are coupled antiferromagnetically. The destruction mechanism of the antiferromagnetic ordering is shown to be different between in the hole-doped Cu
2O
11 and in the electron-doped Cu
2O
7 clusters.
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Kenichi Tenya, Hideki Miyajima, Shuetsu Haseyama, Yuuichi Ishikawa, Sh ...
1991 Volume 60 Issue 7 Pages
2324-2332
Published: July 15, 1991
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The magnetic flux pinning force in Tl
2Ba
2Ca
2Cu
3O
x high-
Tc superconductor (
Tc=120 K) were measured as functions of temperature and magnetic field by using a torque magnetometry. The magnetic torque curves exhibit a large rotational hysteresis accompanied with a delayed angle for the rotation of applied magnetic fields. The number density of fluxoids and the pinning force acting on the fluxoids were estimated using a combined model with the Bean model and the Silcox-Rollins model for low and high magnetic field regions, respectively. The pinning force depends on the temperature as (1−
t2)
15⁄2, where
t is a normalized temperature by 80 K. Above 80 K, the pinning force is too small to be observed, and it indicates that the fluxoids may become into a flux flow state.
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Sadao Nakajima, Minoru Sato, Yoshimasa Murayama
1991 Volume 60 Issue 7 Pages
2333-2340
Published: July 15, 1991
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Mean field approximation is applied to nonlinear equations of motion in the holon-spinon operator formalism proposed previously. A simple interpolation scheme, which looks very much like the conventional band theory, is thus established between insulating and metallic limits of the
tJ model. The transport equation of the normal state is given and critical temperatures of
S-wave and
D-wave superconducting states are calculated.
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Manfred Sigrist, Nobuyuki Ogawa, Kazuo Ueda
1991 Volume 60 Issue 7 Pages
2341-2350
Published: July 15, 1991
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In time-reversal symmetric unconventional superconductors time-reversal breaking structures can occur under certain conditions. This effect is demonstrated on two examples: a domain wall and a thin film for a superconductor with an order parameter consisting of two components. It is shown that the occurrence of time-reversal breaking states is compatible with the general stability conditions of a Ginzburg-Landau theory.
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Shigeki Ohsugi, Yoshio Kitaoka, Kenji Ishida, Kunisuke Asayama
1991 Volume 60 Issue 7 Pages
2351-2360
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The nuclear spin-lattice relaxation time
T1 of
63Cu in La
2−xSr
xCuO
4 was measured in the concentration range of
x=0.075∼0.15 near the magnetic phase boundary around
x=0.05. At low Sr concentration and low temperature, (
T1T)
−1 was found to increase markedly with a development of strong antiferromagnetic (
AF) spin correlation among Cu spins. In normal state, (
T1T)
−1 exhibits a temperature dependence of
C⁄(
T+θ) associated with the
Curie-Weiss law of the staggered susceptibility χ
Q(
T) at the zone boundary,
Q=(π⁄
a, π⁄
a), above 60 K and approaches a nearly constant value in a narrow
T-region just above
Tc.
Tc decreases with decreasing θ, becoming zero at
x=0.05 when θ is extrapolated to zero. The rapid decrease of 1⁄
T1 below
Tc has commonly been observed irrespectively of further development of the
AF correlation with decreasing Sr content.
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Masukazu Igarashi, Fujio Tsuruoka, Hidekazu Tanaka, Yoshitami Ajiro, K ...
1991 Volume 60 Issue 7 Pages
2361-2370
Published: July 15, 1991
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Magnetic phase diagram of the quasi-one-dimensional antiferromagnetic mixture CsMn
1−xCo
xCl
3·2H
2O has been studied through the magnetic susceptibility measurement and neutron diffraction experiment. The
x-
T diagram essentially consists of two parts, one for
x<0.1 already reported and the other
x>0.1. For
x>0.1,
TN increases with increasing
x, reaching a broad maximum at about
x=0.45 and then decreases as
x approaches 1.0. Between the two different magnetic structures for
x=0.1 (C-structure) and for
x=1 (D-structure), a modurated structure described as antiferromagnetic chains extending in the
a-direction coupled ferromagnetically along the
c-direction and arrayed in an up-up-down-down manner along the
b-direction has been observed.
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Keiichiro Oguchi, Keisuke Tajima, Yoshio Shinoda
1991 Volume 60 Issue 7 Pages
2371-2379
Published: July 15, 1991
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The first order magnetic transition of spiral to ferromagnetic structure of Dy-4%Y alloy, which is induced by both temperature and magnetic field, has been investigated by means of X-ray diffraction and magnetization measurement. The development of the ferromagnetic phase could be studied by X-ray diffraction measurement for the observation of the hexagonal to orthorohmbic crystal distortion accompanying the first order magnetic transition. Below
Tc, the ferromagnetic and spiral phases coexist down to 10 K and the latter was found to be in a meta-stable state. The development of the ferromagnetic phase induced by both temperature and magnetic field exhibits a time dependent behavior and is proportional to log
t. The results are discussed with the one dimensional kink model assuming the “spin slip” in the spiral phase.
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Hiroyuki Nojiri, Makoto Uchi, Sigeki Watamura, Mitsuhiro Motokawa, Hid ...
1991 Volume 60 Issue 7 Pages
2380-2387
Published: July 15, 1991
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A determination of magnetic structures of metamagnetic PrCo
2Si
2 has been made in high fields up to 16 T by using a pulsed high magnetic field system developed by the present authors. It has been confirmed that the complicated magnetic structures in high fields obtained by this experiment are identical with those suggested by high field magnetization measurement. The maximum field in this experiment is the highest one reported so far as the magnetic field used for the neutron diffraction experiments and it has been turned out that the pulsed field method is useful to determine the magnetic structures in high field phases.
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Riichiro Saito, Koichi Kusakabe
1991 Volume 60 Issue 7 Pages
2388-2393
Published: July 15, 1991
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We propose
non-orthogonal spin 1/2 functions of
N spins with the total spin
Stot=
S, and its
z components of
Sztot=
M, which are generated by the standard tableaus of Young’s diagrams of the symmetric group. The proof that the spin functions form a complete set of the space of {
Stot=
S,
Sztot=
M} is presented in terms of permutation operators of the symmetric group.
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Hiroshi Shimahara, Satoshi Takada
1991 Volume 60 Issue 7 Pages
2394-2405
Published: July 15, 1991
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The two dimensional Heisenberg model is studied with a Green’s function decoupling scheme in the ferromagnetic and the antiferromagnetic cases. We employ Kondo and Yamaji’s formulation and improve it quantitatively. The present theory does not violate the rotational symmetry and the sum rule of the correlation function. We calculate excitation spectrum, long range order, correlation functions, correlation length, energy, and spin susceptibility. The results are compared with those of the Monte Carlo simulations and the experiments of La
2CuO
4. Qualitative and semi-quantitative agreements are obtained. In particular, the temperature dependence of the susceptibility indicated by Monte Carlo simulations is reproduced over all temperature region.
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Kazuyoshi Yamada, Ken-ichi Takada, Syoichi Hosoya, Yousuke Watanabe, Y ...
1991 Volume 60 Issue 7 Pages
2406-2414
Published: July 15, 1991
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The structure and magnetic properties of Bi
2CuO
4 have been studied by neutron and X-ray diffraction, magnetic susceptibility and magnetization measurements. Three-dimensional (3D) and anisotropic antiferromagnetism is revealed for this compound rather than the previously anticipated one-dimensional one. Long-range antiferromagnetic order associated with a ferromagnetic stacking of Cu
2+ spins along the [001] axis starts to develop below
TN=42 K. A magnetic moment of 0.85±0.05 μ
B/Cu which is larger than those of Cu
2+ spins in the two-dimensional Heisenberg antiferromagnets such as La
2CuO
4 and Sr
2CuCl
2O
2 reflects the 3D character in Bi
2CuO
4. A non-linear magnetization curve under an inplane magnetic field is analyzed quantitatively by a continuous spin rotation in the (001) plane.
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Michio Kondo, Yosio Nisida
1991 Volume 60 Issue 7 Pages
2415-2423
Published: July 15, 1991
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Photo-magnetic (PM) effect is a change in magnetization which arises from spin reversal or orbital diamagnetism associated with optical excitation and subsequent relaxation processes. The PM effect on shallow impurities in silicon has been studied using a SQUID magnetometer. The SQUID-ESR has been also carried out to elucidate the origin of the PM effects. We have attempted to interpret the experimental results in terms of either the orbital diamagnetism of D
− states or the unthermalized donor spins. Consequently we conclude that the PM effect arises from the unthermalization of donor spins which is induced by the spin-exchange scattering between donors and photoexcited hot carriers. Based on this model, rate equation approximation is discussed.
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Shin’ichi Ishimaru, Nobuo Nakamura, Hideaki Chihara
1991 Volume 60 Issue 7 Pages
2424-2428
Published: July 15, 1991
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The dependence of the
1H spin-lattice relaxation rate (
T1−1) on temperature and frequency was measured in phenothiazine crystal in order to help clarify the mechanism of the ferroelastic phase transition on this material.
T1−1 in the low temperature phase shows the completely opposite frequency dependence to what the usual theory for
T1−1 based on thermal molecular motion expects. Such novel behavior of
T1−1 can be explained by the existence of a central-mode, and analysis of
T1−1 in the high temperature phase according to the central-mode theory led to the critical exponent of −1.0.
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Akira Yoshihara, Toru Otake, Tadao Fujimura
1991 Volume 60 Issue 7 Pages
2429-2436
Published: July 15, 1991
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Thermal magnons within the optical skin layer of ferromagnetic MnP single crystal (
Tc∼290 K) have been studied by Brillouin light scattering in a temperature range between 80 K and 310 K under zero magnetic field. For temperatures below ∼
Tc⁄2, the magnon energy gaps obtained from Brillouin scattering show good agreement with the bulk magnon gaps obtained from neutron scattering and torque method. Well below the Curie temperature, Brillouin scattering has been established as a convenient technique to determine the energy gaps in itinerant ferromagnets. The spins near the surface seem to undergo a surface magnetic phase transition at much lower temperatures than the bulk
Tc. A complete set of the elastic constants at room temperature has been determined.
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Tetsuhiko Tomiki, Hideki Akamine, Mitsuhiko Gushiken, Yasunobu Kinjoh, ...
1991 Volume 60 Issue 7 Pages
2437-2445
Published: July 15, 1991
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The optical absorption spectrum (2 eV∼6.8 eV), the Ce
3+ emission spectrum (1.8 eV∼2.7 eV) and the excitation spectrum for the 550 nm Ce
3+ emission (2.4 eV∼6.3 eV) have been measured on single crystals of YAG:Ce
3+. The excitation spectrum for the 550 nm emission (2.7 eV∼11.2 eV) is also reported on powder phosphor of YAG:Ce
3+. With the use of these data, the energy position of all the five
d lines of the Ce
3+ centre, including the highest energy component of the
dε which has not been found hitherto, could be determeined. The crystalline field splitting, 10
Dq, of the
d levels of the Ce
3+ centre is thereby estimated as 2.22 eV. Further, the energy location of the lowest energy component of
dγ after the relaxation has been estimated.
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Takeshi Morimoto, Meiro Chiba
1991 Volume 60 Issue 7 Pages
2446-2460
Published: July 15, 1991
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Stimulated, interband Landau emission originating from excitation of electrons and holes by the action of the
J×
H force at the quantum limit has been observed, accompanied by a remarkable current saturation in the
V-
I curve, for the first time in bulk
n-type InSb at 4.2–135 K when passing a current density
J as low as 16–40 A/cm
2 in perpendicular to a magnetic field
H up to 7 T. Such an outstanding low value of the critical current density
Jc for lasing is considered to originate from extremely high value of the density of states of electrons populated in the lowest Landau level at the quantum limit. In addition to the tunability of the emission frequency controlled primarily by the magnetic field, lowering of Landau levels, which results in a virtual decrease of the energy gap of about 20 meV at around
Jc for
H=7 T, has also been observed in proportion to the current densities. The lowering of Landau levels can be interpreted in terms of the action of the strong electric field induced along
J×
H direction.
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Shin Arahira, Yoshiaki Uesu
1991 Volume 60 Issue 7 Pages
2461-2469
Published: July 15, 1991
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All independent components of the second-order nonlinear optical (SHG) tensors and Miller’s constants of Ca
2Pb(C
2H
5CO
2)
6 (DLP) were determined in the temperature range from −60°C to 90°C. Both in paraelectric and ferroelectric phases, the components
d11 and
d14 which are forbidden by symmetry and Kleinmann’s condition were also observed. Precise examination revealed that the phenomenon originated from the symmetry-lowering as a result of a strong internal electric field produced in the DLP crystal. By annealing the crystal at 250°C, the effect of symmetry-lowering could be diminished. The temperature dependence of the SHG tensors was analyzed by the bond-charge theory where Pb–O and Ca–O bonds were assumed to be the main contributions to the observed tensors. Opposite signs of the two-bond contributions cause the anomalous temperature dependence of the SHG tensors.
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Shin-ichi Furusawa, Hisaaki Hayasi, Yoshihiro Ishibashi, Akio Miyamoto ...
1991 Volume 60 Issue 7 Pages
2470-2474
Published: July 15, 1991
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The temperature dependence of Raman spectra of potassium titanyl phosphate (KTiOPO
4:KTP) was measured in detail at temperature range from 300 K to 1100 K. The frequency shift of the
A1 modes was measured as a function of temperature. No soft mode was observed.
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Giovanni Fazio, Giorgio Giardina
1991 Volume 60 Issue 7 Pages
2475-2476
Published: July 15, 1991
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Satoshi Kanai, Yoshimi Tsuchiya, Masayuki Hasegawa
1991 Volume 60 Issue 7 Pages
2477-2478
Published: July 15, 1991
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Ryouichi Uriu, Daisuke Shimada, Nobuo Tsuda
1991 Volume 60 Issue 7 Pages
2479-2480
Published: July 15, 1991
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Shigenori Tanaka, Noburu Fukushima, Hiromi Niu, Ken Ando
1991 Volume 60 Issue 7 Pages
2481-2482
Published: July 15, 1991
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