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Kêitsiro Aizu
1976 Volume 41 Issue 1 Pages
1-8
Published: July 15, 1976
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Following the preceding papers, the present paper is also concerned with homophone sequences of phase transitions, but assumes the soft modes more concretely to be of wavenumber zero. For every possible specification of both the point group of the prototypic phase and the irreducible representation for the soft modes, the pedigree is determined. Discussions are made about three typical cases in which the soft modes are threefold degenerate.
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Akira Onuki
1976 Volume 41 Issue 1 Pages
9-17
Published: July 15, 1976
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An explicit general expression is derived for the logarithmic term in the density expansion of transport coefficients of a gas. It is also shown that the collision processes contributing to the logarithmic term determine the behavior of the memory function associated with the one-body distribution function in the time region longer than the duration time of a binary collision and shorter than the mean free time.
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Yoshiichi Fukuda
1976 Volume 41 Issue 1 Pages
18-25
Published: July 15, 1976
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The frequencies of localized and resonance modes in the honeycomb lattice are calculated. The effects of change of mass and force-constant due to impurity atom are studied. It is shown that in the case of honeycomb lattices an impurity atom brings about an s-like and two p-like localized modes, while in the case of the triangular lattices an impurity atom produces an s-like, two p-like, two d-like and an f-like modes.
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Yuji Asada
1976 Volume 41 Issue 1 Pages
26-31
Published: July 15, 1976
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The specific heat of Pr
xCe
1−xRu
2 (0.0
≤x≤0.4) were measured from 1.3 to 20 K. The effective electron-electron interaction in BCS theory decreases monotonically with increasing
x. The increase of the superconducting transition temperature for low Pr concentrations depends mainly on the increase of the γ value. The magnetic contribution to the specific heat was observed for
x≥0.2. The transition to the superconducting state becomes broad abruptly beyond
x=0.3, which is related to the magnetic ordering of Pr. The magnetic properties were measured for 0.0
≤x≤1.0. Praseodymium possesses the magnetic moment of 3.57 μ
B for all alloys. This value is very close to that of Pr
3+. In this alloy system the magnetic interaction destroys the superconductivity before the ferromagnetism occurs.
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Nobuyoshi Sakamoto, Fujio Irie, Kaoru Yamafuji
1976 Volume 41 Issue 1 Pages
32-38
Published: July 15, 1976
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The flux flow voltage in a foil of type II superconductor has been shown to suffer a remarkable modification by the application of a small ac magnetic field, even if the frequency is much less than the depinning frequency.
In this paper, two types of simple phenomenological theories are derived in the presence of an ac field parallel to the foil by starting from different extreme assumptions. The results of the measurements in this configuration are also presented. The comparison with the present theories shows clearly the applicable ranges of these theories. The present conclusions also suggest the limitations of existing theories for other configurations started from similar assumptions.
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Yoshikazu Endo
1976 Volume 41 Issue 1 Pages
39-43
Published: July 15, 1976
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Localized magnons around an impurity spin in a linear Heisenberg ferromagnet are investigated up to three-magnon states. The easy axis of the host spins is assumed to be in the
z direction, while that of the impurity spin is in the
xy plane. Two- and three-magnon localized states are obtained by the method similar to that of the one-magnon problem. It can be applicable over the whole intensity region of the single-ion anisotropy constant
D′ of the impurity spin. In case of large
D′, the ground state is a one-magnon localized state when the magnitude
S′ of the impurity spin is 1, while, for
S′=3⁄2, the ground state may be a one- or more-than-one-magnon localized state depending on relative magnitudes of the single-ion anisotropy of the host spins, host-host exchange interactions, and impurity-host exchange interactions.
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Motohiro Matsuura, Yoshitami Ajiro
1976 Volume 41 Issue 1 Pages
44-49
Published: July 15, 1976
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Magnetic basic properties of the crystallographic two sublattice (C
2) system in which magnetic ions at these lattice points have inequivalent
g-tensors, are rigorously studied on the basis of the linear response theory. Such a C
2 system under a uniform field is quite equivalent to a fictitious single lattice (C
1) system under both a uniform and a staggered fields. So in such a C
2 system, the staggered magnetization as well as the uniform magnetization is induced in the paramagnetic state by applying a uniform field. On these facts, a possibility to derive the staggered susceptibility from the experimentally observed uniform and staggered magnetizations was examined based on the symmetry of zero field Hamiltonian of the system. Application of the result to the existing one and two dimensional Heisenberg antiferromagnets is discussed with some promising examples.
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Kazushi Sugawara, C. Y. Huang
1976 Volume 41 Issue 1 Pages
50-53
Published: July 15, 1976
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The crystal-field splittings between the ground and the first excited states Δ of magnetic ions Dy
3+, Er
3+ and Ce
3+ have been acquired from the temperature-dependent ratio of the intensity of the Gd
3+ EPR to the EPR intensity of the magnetic ions. From our best fits we obtain Δ≈80 K and 30 K for Dy
3+ in YP and YAs, respectively; Δ≈45 K and 22 K for Dy
3+ in LaP and LaAs; Δ≈120 K and 70 K for Er
3+ in YP and YAs; and Δ≈22 K for Ce
3+ in LaSb.
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Yosiaki Tino, Yukihiro Nakaya
1976 Volume 41 Issue 1 Pages
54-58
Published: July 15, 1976
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As well known, the two-phase transformation γ→α+γ is extremely difficult to cccur in the Fe–Ni system, leading to an enormous thermal hysteresis. The nature of this unusual process as well as of the 36%Ni–Fe Invar alloy were studied by annealing the γ-phase Invar alloys in the two-phase region for long duration. A “tail part” in the magnetization(M)-temperature(T) curve was found to grow through three stages; first, a reversible tail becomes large, and then it begins to show a thermal hysteresis, finally it tends to disappear in the third stage. The X-ray spectra suggest that at first an imperfect γ→α lattice transformation occurs locally, and then the diffusion of concentration seems to start, where the distortion of the lattice becomes large due to local transformation. It is likely that the 36%Ni–Fe alloy contains a region corresponding to the tail in the M–T curve.
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Yosiaki Tino, Masaaki Kobayashi
1976 Volume 41 Issue 1 Pages
59-65
Published: July 15, 1976
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The effect of cold-swaging on the low thermal dilatation in the Fe–Ni Invar alloys, especially the negative dilatation of the 36%Ni alloy, was investigated by the X-ray and magnetic measurements as well as the thermal expansion measurements in the directions perpendicular and parallel to the swaging direction. Anomalies of the α→γ transformation were found in the irreversible alloy, which behaves as including higher
Af-points or lower nickel contents. The γ-phase alloy after this transformation includes presumably lower Curie points. For the 36%Ni alloy, a swelling portion was found in the magnetic susceptibility in the para-process versus temperature curve in a lower temperature range, which is in agreement with the range of the negative dilatation. To explain such a state, a shear mechanism was discussed.
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Kazuo Ohishi
1976 Volume 41 Issue 1 Pages
66-71
Published: July 15, 1976
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The effects of hydrostatic pressure on the first magnetocrystalline anisotropy constant
K1 were measured on both Ni–Pd (∼40 at.%Pd) and Ni–Cu(∼19 at.%Cu) alloy systems in Ni rich regions by torque method. Measurements were made under pressures up to 6 k bar at 77 K for both Ni–Pd and –Cu alloys and at 273 K for Ni–Pd alloys. The pressure derivatives of
K1, ∂
K1⁄∂
P, are all positive in sign for both alloy systems. At 77 K, ∂
K1⁄∂
P increases rather slowly with Pd content for Ni–Pd alloys, but it decreases rapidly with Cu for Ni–Cu alloys. The positive shift of
K1 with pressure and the different behaviour of ∂
K1⁄∂
P at 77 K for both alloy systems are discussed qualitatively on the itinerant electron model.
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Katsuyasu Kawano, Ryohei Nakata, Minoru Sumita, Eiichi Higuchi
1976 Volume 41 Issue 1 Pages
72-78
Published: July 15, 1976
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In RbCl: Eu
2+ crystals, there are found three groups of EPR spectra with an intensity ratio of 2:1:1, which are attributed to off-center displacements of Eu
2+ ions along [111] axis from normal lattice sites.
The spectra of the off-center Eu
2+ ions can be described by combining the spin Hamiltonian in an orthorhombic field and the perturbation terms depending on the magnetic field as follows; (
Remark: Graphics omitted.), where
g=1.995,
b20=294.6,
b22=−139.8,
A151=−31.3,
u=−0.2∼0.9,
U=0∼−0.05 (10
−4 cm
−1) at room temperature. The displacement is estimated from the angles between the principal axes and [110] directions to be 0.082
a (
a: anion to cation distance), and the induced dipole moment to be 2.57 Debye. Thermal stabilities of the off-centers are discussed in the temperature range between room temperature and 150°C.
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Shoichi Shimizu, Yuichiro Murakami, Sukeji Kachi
1976 Volume 41 Issue 1 Pages
79-84
Published: July 15, 1976
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Cu
50−xNi
xZn
50 β phase alloys undergo a martensitic transformation from the CsCl-type ordered cubic (B2 structure) to the AuCuI-type tetragonal (L1
0 structure). The martensite L1
0 phase appears at room temperature when Ni composition
x becomes larger than 32.5 at.%, i.e. when electron atom ratio (
e⁄
a) becomes smaller than 1.175. In order to clarify the origin of B2–L1
0 transition, composition and temperature dependence of the elastic constants in Cu
50−xNi
xZn
50 alloys were measured. The elastic constant
C′=(
C11−
C12)⁄2 decreases with increase in
x and d
C′⁄d
T is positive (i.e. lattice softening) in the cubic phase, which are suggested to have an important role on the martensitic transformation in these alloys.
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Rayji Yamada, Noboru Watanabe, Kentaro Sato, Hajime Asano, Makoto Hira ...
1976 Volume 41 Issue 1 Pages
85-90
Published: July 15, 1976
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The local vibration spectra of hydrogen atoms dissolved in tantalum have been studied by the energy-loss scattering of pulsed neutrons. The observed time-of-flight spectra show split peaks of the local modes near 120 and 175 meV, which are almost invariant with changing concentration (H/Ta=0.1, 0.5 and 0.7) and configuration of hydrogen at 20° and 85°C. From comparison with previous neutron results on niobium and vanadium hydrides, it is shown that the energies of the split local modes are nearly independent of the metal-hydrogen distance, and the relative intensity and the FWHM of the high energy mode increase in the disordered phase at 85°C in comparison with the ordered phase at 20°C.
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Masamichi Morimoto, Koichi Shindo, Akira Morita
1976 Volume 41 Issue 1 Pages
91-99
Published: July 15, 1976
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Density functional formalism developed by Hoenberg, Kohn, and Sham is applied to the calculation of the surface tension of electron-hole droplets in anisotropic semiconductors. It is shown that the droplet warps because of the anisotropy of electron mass parameters. The shape of droplets in highly excited Ge under an uniaxial stress of about 0.3 kbar along the [111] direction is of the shape of oblate spheroid. The ratio of the minor axis to the major one is estimated to be 1.2∼1.9 under the assumption of local neutrality. The shape of droplets in Si under an uniaxial stress of about 1.5 kbar along the [111] direction is also shown to be oblate spheroid with the axis ratio less than 1.54. Determination of the shape of droplets by the light scattering experiment is discussed.
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Fujio Minami, Yasuo Oka, Takashi Kushida
1976 Volume 41 Issue 1 Pages
100-108
Published: July 15, 1976
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Optical spin orientation experiments have been made in GaSe under longitudinal and transverse magnetic fields at 4.2 K. From the results, the lifetime and the spin relaxation time of the direct exciton are determined to be of the order of 10
−9 s at zero magnetic field. The polarized luminescence spectrum due to the difference of the thermalized populations and that due to the spin memory have been obtained separately under longitudinal magnetic field. This makes it possible for the first time to determine the depolarization factor due to the origins other than the spin relaxation in the emitting state and also the correlation time of the random local field modulation which is responsible for the spin relaxation. Theoretical magnetic field dependence of the degree of polarization of luminescence is derived and compared with experiments for the free exciton line.
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Ko Sugihara, Madoka Tokumoto, Chikako Yamanouchi, Kazuo Yoshihiro
1976 Volume 41 Issue 1 Pages
109-115
Published: July 15, 1976
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Longitudinal magnetoresistance is measured in
n-InSb crystals with carrier concentration ranging from 7.5×10
13 to 9×10
15 cm
−3 at 4.2 K∼300 K. Magnetic fields up to 120 kOe are employed. Some samples exhibit negative magnetoresistance even at 200 K. By making use of the solution of the Boltzmann equation derived from the truncation of the infinite difference equation, the observed results can be qualitatively explained.
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Osamu Sueoka, Shoichiro Koide
1976 Volume 41 Issue 1 Pages
116-121
Published: July 15, 1976
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The mobility of a thermal positron in diamond is studied theoretically and experimentally. An approximate wave function of a positron is obtained by the Wigner-Seitz method for an effective hard sphere potential with radius determined by the WKB method. The dilatation due to the acoustic wave gives rise to a change in the energy determined as a function of the Wigner-Seitz cell radius, which yields the positron-phonon interaction of the deformation potential type. The estimated mobility has ambiguities but may have the order of magnitude 50∼500 cm
2/volt · sec. The experimental value of the mobility obtained by means of the angular correlation in positron annihilation is less than 20 cm
2/volt · sec at room temperature, much smaller than the mobility 1200 cm
2/volt · sec of a hole in the valence band.
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Fusayoshi J. Ohkawa
1976 Volume 41 Issue 1 Pages
122-129
Published: July 15, 1976
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The electronic structures of the subbands of
p-channel inversion layers of silicon are calculated by including an image potential and a many-body interaction. The effects of the image potential and the many-body interaction are as large as the typical energy separation between the subbands. Optical spectra are calculated and compared with the experiment by Kamgar
et al. A quantitative agreement between the theory and the experiment is obtained. Many-body effects on the quasi-particle mass are shown to be small except in a very low surface carrier concentration, and the validity of the previous results concerning cyclotron masses obtained in the Hartree approximation is confirmed.
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Kunio Wakamura, Toshihiro Arai, Keiei Kudo
1976 Volume 41 Issue 1 Pages
130-136
Published: July 15, 1976
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The vibrational frequencies of infrared-active modes in ferromagnetic crystals, HgCr
2Se
4 (Curie temperature
Tc=120 K) and CdCr
2Se
4 (
Tc=130 K), have been measured in the temperature range of 300 K to 85 K. To compare their behaviours with those in non-magnetic crystal, the same measurement has been made for CdIn
2S
4. All the measured frequencies increase continuously with decreasing temperature. In the magnetic crystals, the frequencies indicate some anomalous shifts to the higher frequency side (0.4∼0.6 cm
−1) near
Tc. Such anomalous shifts are proportional to the magnetizations of magnetic crystals: this anomalous shift has not been observed in CdIn
2S
4. The value of the continuous frequency shift is estimated from the mode-Grüneisen parameter and the variation of volume determined by an X-ray technique. The anomalous shift is explained phenomenologically by using an expansion of the atomic potential with respect to the magnetization.
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Toshio Bandai, Hirohito Fukutani, Goro Kuwabara
1976 Volume 41 Issue 1 Pages
137-142
Published: July 15, 1976
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The stress-induced linear dichroism (SLD) of the
1E
a band in the antiferromagnetic KNiF
3 is studied under the 〈001〉 and 〈111〉 stress. The large SLD, which is non-linear to the stress, is explained as due to the reorientation of the collinear spins toward the direction of the stress. The analysis of the SLD leads to the assignments of the structures of the
1E
a band. The band located at 634.5 nm consists of an overlap of a T
1u phonon-assisted electric dipole transition and a magnon sideband. The band at 619.5 nm arises from an exciton-magnon-phonon transition.
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Yasuo Sakisaka, Takehiko Ishii
1976 Volume 41 Issue 1 Pages
143-151
Published: July 15, 1976
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It has been found that the optical absorption spectra of CoX
2(X≡Cl or Br) evaporated on substrates of KX or RbX change drastically when samples are annealed above 70°C. An analysis of X-ray photoemission lines of core levels indicates that the change is caused by the formation of a new compound as K
2CoX
4 or RbCoX
3. The chemical reactions, CoX
2+KX→K
2CoX
4 and CoX
2+RbX→RbCoX
3, proceed fast above 80°C. The major results include the intense crystal-field bands in the 1.5–2 eV region arising from 3
d electrons of Co
2+ occupying tetrahedral sites and the
p→
d charge-transfer bands above 4 eV, as well as the X-ray photoemission spectra of valence electrons. The
f-values of the
d→
d transitions are of the order of 10
−3. All of the observed spectra are interpreted in terms of the localized excitation in a CoX
42− complex-ion.
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Akio Honma, Satoshi Ooaku
1976 Volume 41 Issue 1 Pages
152-161
Published: July 15, 1976
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The line shape functions for the B-band with and without the effect of magnetic field are studied theoretically by use of the perturbation theory and the classical Franck-Condon approximation. The sum of the linear electron-lattice interaction and the Zeeman energy is treated as the perturbing Hamiltonian through which the mixing of the A- and C-states into the B-state occurs. Because of its vibration-dependent transition moments, the B-band is found to have the following characteristics. Although the
T2g mode is responsible for the structure of the absorption spectrum, the
Eg mode gives the similar shape of the magnetic circular dichroism (MCD) spectrum to that due to the
T2g mode. In comparison with the A- and C-bands, the structure of the absorption spectrum is indistinct, while the shape of the MCD spectrum is complicated and very strange. The calculated spectra explain satisfactorily the experimental ones.
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Seiji Kojima, Kikuo Ohi, Terutaro Nakamura
1976 Volume 41 Issue 1 Pages
162-166
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The temperature dependence of electrooptic coefficient
z63 and spontaneous birefringence
ΔnxyS is determined by static measurements on a single-domain and mono-phase region of a GMO crystal under the temperature control with the precision of ±10
−2°C, so that the thermal hysteresis of about 0.1°C is clearly observed at the transition. Results on
z63 are in good agreement with those of Fousek’s dynamical measurements within experimental uncertainty. The third power of
ΔnxyS decreases linearly with increasing temperature in the neighborhood of the transition point. Temperature dependence of
z63 and
ΔnxyS is qualitatively explained by Aizu-Dvo\v{r}ák’s theory.
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Yasuharu Makita, Akikatsu Sawada, Yutaka Takagi
1976 Volume 41 Issue 1 Pages
167-173
Published: July 15, 1976
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Dynamical properties of mechanical twins in (NH
4)
2SO
4 have been studied using a polarizing microscope both in the paraelectric and ferroelectric phases. It has been found that both {011} and {031} twins can be introduced into an originally untwinned crystal, and twin planes once introduced can propagate through the crystal by application of mechanical stress. The threshold stress necessary to move twin planes was found to increase with decreasing temperature, but did not show any abrupt jump at the ferroelectric transition point. It is suggested by considering twinning condition that propagation of twin planes is accompanied with the reorientation of tetrahedral molecules SO
4−−.
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Akikatsu Sawada, Yasuharu Makita, Yutaka Takagi
1976 Volume 41 Issue 1 Pages
174-180
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We have found that, if in (NH
4)
2SO
4 a hexagonal phase happened to exist somewhere on higher temperature side, we can explain group-theoretically various experimental results of mechanical twins observed in (NH
4)
2SO
4 crystals as straightforward consequences of a hypothetical hexagonal-orthorhombic phase transition. The transition occurs through an instability at the
M point of the Brillouin zone. The microscopic picture of the transition may be the ordering in the orientations of the tetrahedral SO
4−− ions.
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Kêitsiro Aizu
1976 Volume 41 Issue 1 Pages
181-187
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Even if two different sets of degenerate soft modes are severally of \bar
nM=∞ for ferroelectricity or, in other words, are each neither normally nor faintly ferroelectric, it is possible that some condensation of both sets produces a ferroelectric phase, where it is immaterial whether this condensation of both sets is simultaneous or successive, and (if successive) which set condenses earlier and which later. Examples are presented and discussed. For convenience’ sake, the concept of faintness index which has been introduced for
monophone cases (i.e., cases that the soft mode system consists of only one set of degenerate modes) is extended to
diphone cases.
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Jun Hatano, Fujio Suda, Hideo Futama
1976 Volume 41 Issue 1 Pages
188-193
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The domain wall energy as a function of wall orientation in triglycine sulfate (TGS) crystals has been calculated on the basis of the Zhirnov-type continuum theory. Contrary to the Fousek’s misleading conclusion [Japan. J. appl. Phys.
6 (1967) 950.], the isotropic treatment of the correlation-energy coefficient κ gives an inadequate result to explain the observed wall orientation which is nearly perpendicular to the crystallographic
c axis. An anisotropy of κ has been reasonably introduced; a wall orientation consistent with the observations has been successfully brought about. The anisotropies of the dielectric, elastic and electrostrictive constants of TGS rather ineffectively contribute to the orientation of the domain walls.
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Akihiko Hattori, Masao Tomura, Osamu Fujii, Hitoshi Nishimura
1976 Volume 41 Issue 1 Pages
194-201
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Luminescence and excitation spectra of intrinsic and extrinsic luminescences of RbI crystals are studied in a temperature range of 2.5∼80 K. Under the excitation in the first exciton absorption band, only one luminescence at 3.03 eV is observed in an undoped crystal. This luminescence is ascribed to the self-trapping of a free exciton to a lattice site. In Tl
+ doped crystals under the excitation in the exciton absorption band, the 3.03 eV luminescence decreases and conversely the Tl
+ luminescence increases with the increase of the Tl
+ concentration, while the total yield of both luminescences remains constant. It is concluded that the induced Tl
+ luminescence is the result of the exciton diffusion. The diffusion coefficient of the free exciton is found to be proportional to (
Remark: Graphics omitted.) below 20 K and above that temperature to (
Remark: Graphics omitted.) in which hω is the energy of the longitudinal optical phonon.
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Mareo Ishigame, Masahisa Kojima
1976 Volume 41 Issue 1 Pages
202-210
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The second-order Raman spectra of the thorium dioxide crystal have been investigated. The results are interpreted in terms of the phonon energies near the Brillouin zone boundaries and the zone center, which have been calculated by using Born-von Karman force model. A nearly complete interpretation of the spectra is given. The observed polarization of Raman spectra is in good agreement with the calculated selection rules for the second-order Raman process at the symmetric points
Γ, M and L.
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Tsuneaki Tsuru, Shin-ichi Kurokawa, Tetsuji Nishikawa, Shiro Suzuki, K ...
1976 Volume 41 Issue 1 Pages
211-218
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An experiment has been made on production of monochromatic gamma rays by strongly collimating the coherent bremsstrahlung from a single crystal of silicon around the beam axis. The internal electron beam with the energy of 1 GeV in the synchrotron was collimated on the crystal target by a set of beam scrapers distributed at the straight sections.
The energy spectrum shows a sharp spike at the photon energy
k=185 MeV with the signal-to-background ratio as large as 12 and the width at the half maximum intensity of
Δk=±8 MeV. The maximum intensity of 2×10
4 photons/MeV · sec has been obtained at the spike.
The obtained spectrum is in good agreement with theory based on Überall’s treatment, if the primary angular divergence of the incident electrons and the multiple Coulomb scattering in the radiator are taken into account.
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Fumiaki Kanô
1976 Volume 41 Issue 1 Pages
219-227
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The transition between the intra β-structure and the random coil of a polyamino chain is discussed. By making use of a propagator method, the partition function is calculated for chain consisting of Gaussian chain portions and β-structure portions.
In our model, there exists a transition point. This β-coil transition may be explained as the transition between a system of one-dimensional sequence and a system of two-dimensional sequence.
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Yoshitsugu Oono
1976 Volume 41 Issue 1 Pages
228-236
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The mean square end-to-end distances 〈
R2〉∝
N2ν and the end-to-end vector distribution functions
P(
R) of a polymer chain at
Θ-point and in the polymer melt are considered in the framework of the self-consistent approximation developed by Edwards. The following conclusions are drawn. i) At
Θ-point 2ν=1, but
P(
R) is not gaussian in three dimensional space. ii) In the melt 2ν=1 and
P(
R) is very close to gaussian in three dimensional space. iii) The mechanisms making 2ν unity in the two cases above are different and hence 〈
R2〉 are generally different in these two cases. iv) The parameter
z of the two-parameter theory is not a good parameter for analyzing the data near
Θ-point.
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Birendra Bahadur, Suresh Chandra
1976 Volume 41 Issue 1 Pages
237-239
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The temperature variation of molar compressibility or Wada constant of three nematic liquid crystals HBT, OBT and EBBA has been reported in mesomorphic and isotropic phases. The Wada constant shows an abrupt fall in the vicinity of nematic-isotropic transition temperature.
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Akio Ishida, Kyoji Nishikawa
1976 Volume 41 Issue 1 Pages
240-246
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Effect of finite perpendicular extent of a cold relativistic electron beam on the two-stream instability excited in a warm plasma is investigated. It is shown that if the beam density profile is sufficiently slowly-varying the fastest growing modes are deeply trapped in the beam region and have growth rates comparable to the maximum growth rate of the usual two-stream instability by a uniform beam. The trapping is due to the frequency downshift of the space-charge wave below the Bohm-Gross frequency in the beam region. Both the dispersion relation analysis based on the WKB approximation and the eigenvalue analysis are presented.
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Toshihide Tsunematsu
1976 Volume 41 Issue 1 Pages
247-253
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A procedure is developed for evaluating the hydromagnetic-instability growth rates of a fixed boundary plasma. The procedure is based on the energy principle. Three components of a plasma displacement are treated as independent variables and are expanded in terms of complete systems of functions. The potential-energy change δ
W and the kinetic energy δ
K are expressed as quadratic forms of the expansion coefficients. The growth rates are obtained by minimizing δ
W⁄δ
K with respect to the expansion coefficients. As an example of application, the growth rates of the Bennett pinch are evaluated for incompressible displacements. Results show that the expansion with only 3 or 4 terms for each variable gives satisfactory values of growth rates.
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Kunizo Ohkubo, Shigetoshi Tanaka
1976 Volume 41 Issue 1 Pages
254-256
Published: July 15, 1976
Released on J-STAGE: June 01, 2007
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The spatial damping of Whistler waves are investigated experimentally in plasma columns with large diameter and high value of ω
p⁄ω
c. The observed strong damping near the resonance is shown to be mainly the electron cyclotron damping.
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Tatsuki Ogino, Susumu Takeda
1976 Volume 41 Issue 1 Pages
257-264
Published: July 15, 1976
Released on J-STAGE: June 01, 2007
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The behavior of the spherical and cylindrical ion-acoustic solitons are studied by the computer simulation using a fluid model as well as the theoretical analysis. The simulated results agree well with those obtained by approximately solving the modified Boussinesq equation.
A small residue of the high or low density is formed for the inward or outward propagation, respectively, after the spherical and cylindrical ion-acoustic solitons propagate. Moreover, the electron plasma and ion-acoustic waves are emitted from the solitons as they propagate inwards or outwards. The amplitude of the soliton such as the ion density does not grow infinitely for the finite ion temperature even when the soliton concentrates at the center. This is because the half width of the maximum amplitude is limitted by the ion Debye length.
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Koji Mio, Tatsuki Ogino, Kazuo Minami, Susumu Takeda
1976 Volume 41 Issue 1 Pages
265-271
Published: July 15, 1976
Released on J-STAGE: June 01, 2007
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The basic nonlinear equation which describes the Alfvén waves, with small but finite amplitude propagating along the magnetic field in cold plasmas, is derived modifying the reductive perturbation method proposed by Taniuti and Wei. Then as a result, the nonlinear dispersion relation is obtained through a procedure which clarifies the physical meaning. Furthermore, the modified nonlinear Schrödinger equation which describes the modulated Alfvén wave more correctly than the previous works is proposed. An example of the nonlinear phenomena is shown by the numerical calculations of the initial value problem, using our basic equation for the Alfvén waves.
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Mitsuo Kono, Nobuo Yajima
1976 Volume 41 Issue 1 Pages
272-280
Published: July 15, 1976
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The ion-acoustic wave propagation in a field of randomly excited low-frequency waves (phonon gas) is investigated, by obtaining the linear response function of plasmas in a turbulent phonon state. The turbulent phonons have an influence on the propagation of the coherent wave, to lead a decreased phase velocity. The coherent wave becomes unstable due to the resonant coupling with the beat wave of turbulent phonons. As the result of the instability, the coherent wave with long wavelength piles up in a plasma with turbulent phonons. The results qualitatively agree with the recent experiment.
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Tsutomu Ikemura
1976 Volume 41 Issue 1 Pages
281-291
Published: July 15, 1976
Released on J-STAGE: June 01, 2007
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Spatial behaviors of two electron Langmuir waves parametrically coupled because of the combined action of a density gradient and a high-frequency pump electric field which is uniform outside the plasma are investigated. It is shown that the effective density gradient decreases due to the electron ponderomotive force created by the space-dependent intense pump whose space-dependence is produced by the density gradient, leading to stabilizing effects on the convective-type instability treated in I, because it is excited more strongly, the greater is the density gradient. In a non-magnetized plasma with a monotonously varying density profile, any effective trapping of the instability is shown not to be expected under usual practical conditions. The scale size of the region in which the instability may spread, however, increases with the pump intensity from “smaller than the Airy characteristic length
l” to “much larger than
l.”
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Akio Ishida
1976 Volume 41 Issue 1 Pages
292-299
Published: July 15, 1976
Released on J-STAGE: June 01, 2007
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A general theory of wave energy in a plasma is developed in terms of a linear response of the field intensity to an externally applied infinitesimal disturbance. The theory is applicable to any situations, including the case when the conventional definition becomes invalid. An external disturbance can cause both frequency shift and amplitude change of the wave, and the sign of the wave energy in general depends on their relative importance and hence on the external disturbance. This feature is illustrated for the case of a cold-electron and cold-beam system. For the case when the dielectric function has a small anti-hermitian part, the conventional definition of the wave energy is recovered except for a special case where the frequency shift predominates over the amplitude change.
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Atsushi Ogata, Minoru Sugawara, Tetsuo Watari, Tatsuo Shoji, Shinji Hi ...
1976 Volume 41 Issue 1 Pages
300-304
Published: July 15, 1976
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The theory of the plasma heating by the use of an electrostatic ion cyclotron wave is presented. It provides the optimum heating condition as the interrelation between the plasma density and the
rf frequency. An experiment is carried out based on the theoretical prediction and the result agrees with the theory. The feedback control of the heating is also carried out with the afterglow plasma.
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Akiyosi Itakura
1976 Volume 41 Issue 1 Pages
305-308
Published: July 15, 1976
Released on J-STAGE: May 29, 2007
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A spontaneous electron plasma oscillation in a beam-plasma system can be suppressed by modulating the beam density. In this case small shift of frequency of the oscillation is observed. At the same time oscillations with frequencies 2ω−ω
m and 2ω
m−ω arise, where ω is the frequency of the spontaneous oscillation and ω
m is the modulation frequency. However, oscillations having frequencies ω
m+ω and |ω
m−ω| are not detected. These phenomena are interpreted on the basis of van der Pol equation with a driving term, and a good agreement is found between the theory and the experiment.
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Tetsuya Sato
1976 Volume 41 Issue 1 Pages
309-314
Published: July 15, 1976
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In part I we derive a model nonlinear equation which describes the collective behavior of trapped particles or the nonlinear transport caused by electrostic waves both in a microplasma and in a macroplasma. The equation is found to be approximately of the form,
nt+
annx+
bnxxx2=0. In a Vlasov plasma
n stands for the velocity distribution function modified by narrow-band waves and
x for the velocity, whereas in a magnetized macroplasma
n stands for the density distribution deformed by waves and
x for a coordinate variable perpendicular to the magnetic field. In the course of deriving the nonlinear equation a general formula of saturation amplitudes for collisionless drift instabilities is derived, which is the same as previously derived for collisional drift instabilities. The saturation amplitudes of both collisionless and collisional instabilities are found to be essentially given by (κ
0l⁄2π), κ
0 being the initial logarithmic distribution gradient and
l representing the unstable range in the direction of the density gradient.
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Tetsuya Sato
1976 Volume 41 Issue 1 Pages
315-320
Published: July 15, 1976
Released on J-STAGE: May 29, 2007
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In part II we give some analytical properties and numerical solutions of the nonlinear equation which was derived in the companion paper (part I). As a result of numerical calculations, a new phenomenon is discovered, namely, that a positive pulse and a negative pulse placed separately begin to move in the direction toward each other and annihilate on collision. On the other hand, when only a positive (or negative) disturbance is imposed, it disintegrates into several pulses of the form cos
2x, each pulse running in the same direction with a speed proportional to its amplitude, so that a bigger pulse passes through a smaller one without changing the shape, as the KdV solitons do. When they get together, the amplitude of the combined pulse becomes smaller than the bigger one but the width becomes wider.
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Akira Yoshizawa
1976 Volume 41 Issue 1 Pages
321-327
Published: July 15, 1976
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This paper studies steady homogeneous turbulence by means of a statistical approach. The Liouville equation for the probability distribution function is solved as a perturbation expansion from the Fokker-Planck equation based on turbulent viscosity, turbulent diffusion and three kinds of renormalized vertices. Five nonlinear simultaneous integral equations are derived for these quantities, under the assumption that in the perturbative solution only the first two terms contribute to the second-order velocity correlations (turbulent energy) and the third-order velocity correlations (energy transfer functions). It is shown that the introduction of three kinds of renormalized vertices gives the possibility of removing the effect of the energy-containing range upon the inertial range and of leading to Kolmogoroff’s spectrum consistently.
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Hiroshi Tokunaga
1976 Volume 41 Issue 1 Pages
328-337
Published: July 15, 1976
Released on J-STAGE: June 01, 2007
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The statistical properties of one-dimensional compressible turbulence are investigated by means of the reductive perturbation method and the numerical integration of the governing equations. The mechanical energy of turbulence (
Remark: Graphics omitted.), which is the sum of the kinetic energy and the adiabatic internal energy, is shown to decay in time
t as (
Remark: Graphics omitted.), and the numerical result (
Remark: Graphics omitted.) confirms well this prediction. The kinetic and the adiabatic internal energies are found to oscillate in time with large amplitude around the common average (
Remark: Graphics omitted.), and thus the equipartition of both energies in the average is concluded. The numerically calculated mechanical energy spectrum is expressed as
E(
k)∝
k−2 at low wave-numbers and
E(
k)∝
e−αk, α being a constant, at higher wave-numbers. This behaviour of the energy spectrum reflects the structure of compressible turbulence composed of random trains of shocks and expansion waves.
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K. S. Rama Sastry, D. Premaswarup
1976 Volume 41 Issue 1 Pages
338-344
Published: July 15, 1976
Released on J-STAGE: May 29, 2007
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NQR Zeeman effect studies for the
79Br isotope of Bromine in 2, 4, 6 Tribromophenol were carried out using single crystals. The orientations of the principal
X,
Y, and
Z field gradient axes for all the zero-splitting loci, obtained in the first axis of rotation, were evaluated. An average value of about 0.04 was assigned for the asymmetry parameter of the electric field gradient tensor at the site of the Bromine nucleus. Percentages of single bond, double bond and ionic characters for each of the three C–Br bonds are calculated.
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Ikuo Ono
1976 Volume 41 Issue 1 Pages
345-346
Published: July 15, 1976
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The energy and spin pair-correlation in the ground state and the phase transition for a random mixture of the ferro-antiferromagnets in a quenched Ising system have been investigated by a new idea based on a division of the lattice into elementary units. The effects of the loop proper to the each lattices have been explicity considered. It is demonstrated that the transition temperatures are intimately related to the ground-state energy. Monte Carlo simulations performed on the square lattice are also reported.
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