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Masahiro Kodama
1983 Volume 52 Issue 5 Pages
1503-1504
Published: May 15, 1983
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Day-to-day variations of cosmic-ray-produced neutron fluxes near the Earth’s ground surface are measured by using three sets of paraffin-moderated BF
3 counters, which are installed in the different locations; 3 m above ground, ground level and 20 cm under ground, respectively. Neutron flux decreases observed by these counters when snowcover exists show that there are upward-moving neutrons, that is, ground albedo neutrons near the ground surface. The amount of albedo neutrons is estimated to be about 40% of total neutron flux in the energy range 1–10
6 eV.
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Naoaki Bekki
1983 Volume 52 Issue 5 Pages
1505-1508
Published: May 15, 1983
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Turbulent ionization waves in the positive column of glow discharge are investigated theoretically. It is shown that the turbulent ionization waves can be described by a model of Burgers turbulence. The closed equation by means of the modified cumulant approximation is solved numerically for a typical initial condition. The squared density spectrum is shown to agree with the experimental results.
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Mamoru Yamashita, Hatsuo Kimura
1983 Volume 52 Issue 5 Pages
1509-1511
Published: May 15, 1983
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The reentrant behaviour (Sm C–Sm C
*–Sm C–Sm C
*) observed experimentally in an electric field near the chiral smectic C to smectic A phase transition point is investigated. That curious phenomenon is attributed to the nonlinear excitation of the turn of the director field in the smectic C phase. Similar behaviour near the Lifshitz point in the magnetic field versus temperature plane is also explained by that excitation.
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Hiroshi Niida, Tomiei Hori, Yasuaki Nakagawa
1983 Volume 52 Issue 5 Pages
1512-1514
Published: May 15, 1983
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Magnetization measurements and X-ray diffraction experiments have been made on ε-Mn
3Ga (71.4 at%Mn) having a triangular spin structure with a weak ferromagnetic component below 460 K. It has been found that the D0
19-type hexagonal structure is slightly distorted to an orthorhombic structure below 170 K, and that the transition is accompanied by a steep increase of spontaneous magnetization. The crystal distortion may enhance the deviation from the ideal triangular spin configuration.
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Izumi Tomeno, Sadao Matsumura
1983 Volume 52 Issue 5 Pages
1515-1517
Published: May 15, 1983
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The elastic stiffness
C11 of a single domain LiNbO
3 crystal (
C11E) and that of a multidomain crystal (
C11′) were measured by the ultrasonic phase comparison method in the temperature range between 300 and 1223 K. The stiffness
C11′ was about 2% larger than
C11E at room temperature and the both decreased linearly with increasing temperature. The results indicated that the spontaneous polarization
P3 was approximately constant in the temperature range described above.
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Mikihiko Ikezawa, Yasuhiro Kondo, Ichimin Shirotani
1983 Volume 52 Issue 5 Pages
1518-1520
Published: May 15, 1983
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Using a single crystal of black phosphorus, anisotropic absorption spectra due to the two-phonon summation process have been found in the wavenumber region from 300 to 900 cm
−1. By an oblique incidence method, the dipole moment of an infrared active mode at 470 cm
−1 has been confirmed to be in the z-direction of the crystal as predicted by Kaneta, Yoshida and Morita. Frequencies of unobserved A
u and B
1u modes are estimated to be about 420 and 250 cm
−1 from the absorption spectra of the two-phonon process.
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Keiichi Edamatsu, Mikihiko Ikezawa, Kenji Sato, Shozo Kono, Takasi Sag ...
1983 Volume 52 Issue 5 Pages
1521-1524
Published: May 15, 1983
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Anisotropic fundamental optical absorption bands have been found at 4.4 eV in K
2AgI
3 and Rb
2AgI
3, and at 4.9 eV in Rb
2AgBr
3. The X-ray photoelectron spectrum of Rb
2AgI
3 indicates that the uppermost valence band is the p-band of halogen. Optical absorption spectra are interpreted in terms of transitions of the charge transfer type from the halogen to the silver ion. The photo-excitation in the fundamental absorption region have been observed to induce luminescence and a radiation damage effect at low temperature.
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Shigeru Obayashi, Kunio Kuwahara
1983 Volume 52 Issue 5 Pages
1525-1530
Published: May 15, 1983
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A new two-point implicit scheme for solving the Euler equations was developed, which is second-order accurate in space and time. This is an extension of the MacCormack implicit scheme, and is taking account of the following points; 1. to solve for the physical quantity itself at a new time-step, not for change of the physical quantity in time, 2. to modify the implicit operators for stability so as not to decrease accuracy of the approximation of the first derivative. The resulting method is efficient and easy to program.
This scheme was compared with various other schemes for a shock tube problem. No physically irrelevant pressure distributions of the shock wave obtained by the present method were observed. It was confirmed that the present one produced good results for a large CFL number.
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Sumiyoshi Fujiki, Keisei Shutoh, Yoshihiko Abe, Shigetoshi Katsura
1983 Volume 52 Issue 5 Pages
1531-1540
Published: May 15, 1983
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Monte Carlo simulations of the Ising model on the triangular lattice with the antiferromagnetic nn interaction
J and the ferromagnetic nnn interaction
J′ are carried out. Several physical quantities (magnetizations, energies, susceptibilities, specific heats of sublattices and of the total system) are calculated. A phase which resembles the partially disordered phase proposed by Mekata is observed in the finite temperature region. But it is shown in this region that the sublattice magnetizations vanish at the thermodynamic limit and the Kosterlitz-Thouless phase transition is predicted by the finite size analysis.
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Masakazu Ichiyanagi
1983 Volume 52 Issue 5 Pages
1541-1548
Published: May 15, 1983
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In the spirit of the linear response theory, a simple derivation is given of a Langevin equation for collective modes of a macroscopic system. Unlike in the usual treatment, we separate a weak interaction of individual particles with collective modes which is allowed to depend on time. In nonequilibrium cases, we have shown that a damping constant of the collective modes can be expressed in terms of a time correlation function, in which its average is taken with respect to a nonequilibrium density matrix rather than a usual canonical density matrix. A microscopic expression for a Langevin random force is obtained in terms of fluctuations of a density matrix.
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Osamu Sano, Rhyji Takaki
1983 Volume 52 Issue 5 Pages
1549-1554
Published: May 15, 1983
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Thermochromism in aqueous solutions of cobalt chloride with sodium chloride was used to visualize temperature distributions in liquid. Changes of color of the solution due to temperature variations were observed both by direct photography and by measurements of the transmittance of light. The advantage of the present method is that it visualizes the temperature itself (not its gradient) without giving any disturbance to the fluid. Several examples of applications to typical flows were shown.
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Shinobu Nakazaki
1983 Volume 52 Issue 5 Pages
1555-1562
Published: May 15, 1983
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Usefulness of the first-order exchange Coulomb approximation has been examined by applying it to the electron impact excitation processes of helium-like ions. Collision strengths for the excitation from the ground state to the
n=2 states (2
3S, 2
1S, 2
3P and 2
1P) for Li
+, C
4+, O
6+ and Si
12+ have been calculated at energies up to five times threshold energies. It is found that the present approximation improves the Coulomb-Born-Oppenheimer approximation remarkably and gives results comparable with the five-state close-coupling calculation of Wyngaarden
et al. (1979). It is also found that the short range distortion effect is largely taken care of in the present first-order approximation.
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Kazuhiro Sakimoto
1983 Volume 52 Issue 5 Pages
1563-1571
Published: May 15, 1983
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Several decoupling schemes are discussed for the semiclassical impact parameter treatment of collisions between atoms and linear rigid rotors. First, a decoupling method analogous to the quantum mechanical one originated from the conservation of parity is found also in the semiclassical treatment. Next, presently derived semiclassical versions of
l-dominance and decoupled
l-dominance approximations provide us with an intuitive understanding of the physical meaning of these approximations. Numerical applications are performed for the H
+–CO collision system.
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Hiroshi Kotegawa
1983 Volume 52 Issue 5 Pages
1572-1580
Published: May 15, 1983
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The Coulomb-eikonal approximation is applied to evaluate the electron exchange amplitude in the ionization of hydrogen-like ions by an electron impact. This amplitude is reduced to a three-dimensional integral expression suitable for numerical calculations. The cross section including the contribution of the electron exchange is calculated for the ionization of He
+, whose results show a reasonable agreement with experimental results. The exchange effect is found to be important in the ionization process in the intermediate as well as in the low energy region.
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Nobuo Kobayashi, Tomohisa Nakamura, Yozaburo Kaneko
1983 Volume 52 Issue 5 Pages
1581-1584
Published: May 15, 1983
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Fine-structure transitions, j=3⁄2→1⁄2 and 1⁄2→3⁄2, in the collisions of Kr
+(
2P
j) with rare gases were studied with an ion energy-loss spectrometer in the energy range from 500 eV to 1300 eV. The ions were produced with an electron-impact type ion-source. The fractional ratios of j=1⁄2 to j=3⁄2 states,
N(1⁄2)⁄
N(3⁄2), contained in the primary beam were determined as a function of the electron energy in the ton source from 20 eV to 150 eV. The values were almost constant above the electron energy of 40 eV, and the aberage value of 0.479±0.002 which is close but not exactly equal to the statistical value, 0.5, was obtained. The cross sections for the fine-structure transitions in the collisions of Kr
+ with He were also obtained.
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Takehiko Ishiguro, Takashi Ukachi, Katsuo Kato, Keizo Murata, Koji Kaj ...
1983 Volume 52 Issue 5 Pages
1585-1592
Published: May 15, 1983
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Mechanical kinks are formed in a needle crystal of bis (tetramethyltetraselenafulvalenium) perchlorate, (TMTSF)
2ClO
4, by applying stresses. The kink which has definite angle of 18.4° accompanies antikink with the same angle in the opposite direction. By the X-ray precession photograph, we show that the kink is ascribed to the mechanical twinning with the boundary on the (210) plane. The electrical resistivity measurements in a deformed part lying between the kink and antikink and in a region including the kink were carried out, but they did not show substantial difference compared with those in an underformed part. However, the kink which accompanies distortion in a molecular stack is considered to be one of causes of the resistance jump (stepwise increase in resistance), which is frequently observed during cooling.
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Akio Fukuyu
1983 Volume 52 Issue 5 Pages
1593-1601
Published: May 15, 1983
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The energy spectrum function
E(
k,
t) for one dimensional Burgers’ turbulence is defined as a Taylor series expansion in time variable
t. Assuming a multivariate Gaussian distribution of velocity field at an initial instant, first six coefficients of this Taylor series are calculated explicitly in terms of the initial energy spectrum. To approximate to
E(
k,
t) the Padé approximation is adopted. The numerical results show that a Padé approximant to it is much better than a partial sum of Taylor series as an approximation to
E(
k,
t) for the wave numbers not so large compared with a representative wave number.
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Kenichi Nanbu
1983 Volume 52 Issue 5 Pages
1602-1608
Published: May 15, 1983
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By use of the new direct-simulation method, the exact numerical solution of the Couette-flow problem is obtained over the whole range of the Knudsen number. (The wall Mach number is 3.0) By comparing the obtained solution with the approximate six-moment solution, the accuracy of the latter is examined in detail: as to the flow velocity and shearing stress, the six-moment solution shows reasonable agreement with the simulation solution; as to the temperature, density, and heat flux, the error of the six-moment solution is fairly large in all flow regimes except the near-continuum one; as to the pressure, it is not uniform in the transition-flow regime, differently from the prediction of the six-moment solution.
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Mitsuyasu Yatsuzuka, Kikoh Satoh, Sadao Nobuhara, Kiyoshi Yatsui, Masa ...
1983 Volume 52 Issue 5 Pages
1609-1617
Published: May 15, 1983
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An ion beam modulated near the lower-hybrid frequency is injected into a low-β plasma immersed in a longitudinal magnetic field. Parametric excitation of a drift wave and a lower-hybrid wave is observed. From the measurement of the threshold electric field, an rf field parallel to the magnetic field is found to play an important role in the excitation of the instability. Substantial increase of the ion and electron temperatures has been observed with the growth of the instability. Such a rapid heating may be principally due to the drift wave instability driven parametrically.
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Satoru Iizuka, Koichi Saeki, Noriyoshi Sato, Yoshisuke Hatta
1983 Volume 52 Issue 5 Pages
1618-1628
Published: May 15, 1983
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A systematic experiment is performed on the Buneman instability and the Pierce instability in a bounded plasma consisting of beam electrons and stationary ions. Current fluctuations are confirmed to be induced by the Buneman instability. On the other hand, the Pierce instability gives rise to a current limitation. The phenomena are well explained by Mikhailovskii’s theory taking account of ion motion in a bounded plasma.
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Seiichi Kagoshima, Jean Paul Pouget, Hiroyuki Anzai
1983 Volume 52 Issue 5 Pages
1629-1634
Published: May 15, 1983
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In the organic one-dimensional conductor TMTTF–TCNQ, the 2
kF and the 4
kF CDW were found by the diffuse X-ray photographic method. The 2
kF CDW condenses at 36 K, at which the metal-insulator transition occurs, and forms three-dimensionally ordered structures indicating the occurence of the Peierls transition. A different and unusual temperature dependence is shown by the 4
kF CDW. The transverse ordering of CDW is easily destroyed by the X-ray irradiation. Observed wave number of the transverse ordering and the strong irradiation effect suggest that the 2
kF CDW grows on both TCNQ and TMTTF stacks. However the 4
kF CDW is expected to be present mostly on the TMTTF stack.
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Toyonori Munakata
1983 Volume 52 Issue 5 Pages
1635-1640
Published: May 15, 1983
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Substrate-strain effects on the Frenkel-Kontorova system are investigated under the continuum approximation. Long-wavelength component of the strain field is shown to give rise to an extra biharmonic potential, modifying the basic equation from the sine-Gordon to the double sine-Gordon equation. A kink propagates accompanied by a localized strain field, thus behaving like a kind of polaron. Implication on the commensurate-incommensurate transition studied by Frank and van der Merwe and others is also given.
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Isao Minagawa
1983 Volume 52 Issue 5 Pages
1641-1645
Published: May 15, 1983
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A theoretical study is made of the order-disorder transition of cubic ice Ic, where interaction energies between water molecules are considered, seven order parameters are used, and Takagi’s method is employed. The ordered phase is ferroelectric when the interaction energies between neighbouring molecules are assumed to be the same as that in ice Ih. The transition is of the first order. The Curie-Weiss temperature θ
C is the same as that of Ih in the
c-axis and the transition temperature is 1.29θ
C=59 K. The phase transition from ice Ic to Ih is discussed.
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Mitsuo Harada
1983 Volume 52 Issue 5 Pages
1646-1657
Published: May 15, 1983
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The phase transition at 66°C in RbCuCl
3 has been investigated by X-ray diffraction methods. Structure analyses have been carried out using the photographic data. For high-temperature structure, three equally plausible space groups
P6
3⁄
mmc,
P\bar62
c and
P6
3mc have been examined by a block diagonal least squares refinement. The room-temperature structure has the superstructure with the lattice parameter doubled along the
b-axis and the space group is
Pbcn. The mode analysis of the Jahn-Teller active mode was carried out and the intensity distribution of the superlattice reflections was consistent with the atomic shifts corresponding to the zone boundary
M4+-mode. There exists the second-order piezodistortive coupling between the antiferrodistortive static displacements and the homogeneous strains. From this coupling, the precise temperature dependence of the superlattice reflection is derived.
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Kuniyoshi Ebina, Tuto Nakamura
1983 Volume 52 Issue 5 Pages
1658-1664
Published: May 15, 1983
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Effect of the correlation energy on the Thomas-Fermi-Dirac statistical model of the condensed matter is studied systematically by means of a perturbation method. The pressure curves are obtained with main interest in the low pressure region where the correlation effect is appreciable. The instability of the statistical model occurring at a certain negative pressure is discussed in connection with the thermodynamical stability of electron gas in the outermost region of the Wigner-Seitz sphere, and with the binding problem for an aggregate of atoms at zero pressure.
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Hiroshi Fujiwara, Nobuyuki Nakagiri, Motoyuki Nomura
1983 Volume 52 Issue 5 Pages
1665-1668
Published: May 15, 1983
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The orientation distribution of the {110} diffracted line of the pressure-induced B2 phase of RbCl after B1→B2 transition was measured with an X-ray four-circle diffractometer on which the Merrill-Bassett type diamond anvil pressure cell was mounted. Judging from the {110} pole figure of the B2 phase, the center of which is the [100] axis of the B1 phase, the orientation relation was [111](B2)//[100](B1) and [100](B2)//[111](B1). The result agreed with that obtained by Okai from X-ray diffraction photography.
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Takashi Suzuki, Masahito Yoshizawa, Terutaka Goto, Tsutomu Yamakami, M ...
1983 Volume 52 Issue 5 Pages
1669-1675
Published: May 15, 1983
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The sequence of the structural phase transitions of the layer compound (C
2H
5NH
3)
2FeCl
4 has been determined with the ultrasonic, dielectric and polarized microscope measurements as following; Phase I (
D4h17)—(378.8 K)—Phase II (
D2h18)—(203.5 K)—Phase III—(133.7 K)—Phase IV. The set of the critical exponents obtained with ultrasonic methods are explained by the results of the renormalization group theory on the three dimensional XY model. The ferroelastic domains are observed in the phase II and phse III. The anomaly of the dielectric constant is found near the II–III phase transition point.
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Kibou Ichikawa, Yukio Morii, Tohru Hata, Chiemi Kanamori, Hiroyuki Oka ...
1983 Volume 52 Issue 5 Pages
1676-1681
Published: May 15, 1983
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Nuclear magnetic susceptibility and Zeeman-exchange relaxation time
TZX of solid
3He have been measured by pulsed NMR method using Pomeranchuk cooling technique between 15 mK and 0.97 mK in a static field of about 70 gauss. Magnetic transition to the antiferromagnetic phase was observed at 1.00 mK where the susceptibility decreased to 42% of its maximum value. This drop in susceptibility coincides with the abrupt leveling of
3He pressure in cooling process which shows thermodynamically a phase transition due to abrupt decrease of solid
3He entropy.
The magnitude of
TZX is consistent with the one estimated from BPP (Bloembergen-Purcell-Pound) theory, but the observed temperature dependence can not be explained on this basis.
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Susumu Fukuchi, Yosuke Kayanuma
1983 Volume 52 Issue 5 Pages
1682-1686
Published: May 15, 1983
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The magnetic-nonmagnetic transition of impurities in semiconductors is studied by a simple one-dimensional model. The model is a two-electron system in a linear chain with a short-range impurity potential
v. The intra-site two-body repulsive energy
U is assumed throughout the crystal. The phase boundary for the transition is calculated numerically exactly by the use of the Green’s function formalism. In contrast with the model of Mattis and Lieb, the singlet ground state becomes degenerate with the lowest one-electron scattering state (magnetic) for practically all value of
v as
U exceeds a critical value
Uc which is of the same order of magnitude as
v.
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Sayaka Yoshino, Kozo Hoshino, Masaki Goda
1983 Volume 52 Issue 5 Pages
1687-1691
Published: May 15, 1983
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The properties of eigenvalues and/or eigenfunctions of disordered binary alloys A
xB
1−x with off-diagonal disorder are investigated numerically in the two-dimensional square lattice with 50×50 lattice sites. Special attention is focused on the eigenfunctions near the band edges of A or B subbands when
tAB is much larger than
tAA and
TBB, where
tij’s (
i,
j=A or B) are transfer energies between
i and
j sites. It is shown that the states near the inner band edges are highly localized within A or B atom clusters and the states near the outer band edges are localized within the clusters of atoms connected by AB bonds. The numerical results of the density of states as a function of
tAB are consistent with our previous results and support the importance of the repulsive effect between bands.
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Yasuhiro Iye, Joseph Heremans, Kazuo Nakamura, Giyuu Kido, Noboru Miur ...
1983 Volume 52 Issue 5 Pages
1692-1700
Published: May 15, 1983
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Longitudinal magnetostriction has been measured in bismuth along the binary axis and in graphite along the
c-axis in pulsed magnetic fields up to 40 T. The field dependence of the magnetostriction of bismuth is compared with theoretical calculations based on a model proposed by Vecchi
et al. for the lowest quantum number Landau levels. A better correspondence with the experimental result is obtained by using a set of parameter values recently given by Hiruma
et al. rather than the original Vecchi
et al.’s values. For graphite, a large and field-superlinear magnetostriction has been found.
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Fusayoshi J. Ohkawa, Hidetoshi Fukuyama, Kei Yosida
1983 Volume 52 Issue 5 Pages
1701-1709
Published: May 15, 1983
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Interplay between localization and the Kondo effect has been examined for a model two-dimensional system. Various physical quantities associated with localized spins are calculated perturbatively in terms of exchange coupling constant
J and λ=h⁄2πε
Fτ
0 where ε
F is the Fermi energy and τ
0 is the relaxation time of plane wave states; the susceptibility and the conductivity are shown to have quantum corrections proportional to λ
J2ln
2 (
t) and λ
J3⁄
t, respectively, where
t=h⁄2πτ
0kT.
It is discussed that the ground states of localized spins are qualitatively the same as in pure systems because the ensemble average of local densities of states defined by <<ρ(ε
1,
r)ρ(ε
2,
r)…ρ(ε
n,
r)>> appears to be non zero for any
n in the limit of equal energies, ε
i→ε
F.
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Fusayoshi J. Ohkawa
1983 Volume 52 Issue 5 Pages
1710-1717
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The ensemble average of local densities of states defined by
g2(ε
1, ε
2)=<<ρ(ε
1,
r)ρ(ε
2,
r)>> is theoretically investigated, where ρ(ε,
r) is the local density of states of disordered systems. It is shown by using the self-consistent theory due to Vollhardt and Wölfle and a physical picture of localization due to Mott, which includes the effect of “level repulsion”, that
g2(ε
1→ε
2) is non zero even if the states around ε
2 are localized.
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Kazuhide Tanaka, Takanobu Saito, Masabumi Yasuda
1983 Volume 52 Issue 5 Pages
1718-1724
Published: May 15, 1983
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Electronic states associated with aluminium atoms in ternary Cu–Ni–Al and Cu–Mn–Al alloys with B2 and L2
1 order structures, respectively, were investigated by measuring Al
Kβ emission spectra. The spectra generally consisted of three peaks which changed in strength and in energy (Cu–Mn–Al) systematically with compositions. The lower two peaks were assigned to bonding states of aluminium 3
p electrons hybridizing with the 3
d states of copper and nickel or manganese atoms. These assignments were consistent with a CPA model calculation on the
K emission spectra of transition-transition and transition-simple metal alloys by Kudrnovský, Smrcka and Velický.
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Shigeki Matsunaga, Shigeru Tamaki
1983 Volume 52 Issue 5 Pages
1725-1729
Published: May 15, 1983
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The electrical resistivity of Na–Pb alloys has been measured as a function of temperature and concentration. The curve of the resistivity has a remarkable maximum around the composition of 75 at%Na. The curve of temperature dependence of the resistivity has also a sharp maximum at 80 at%Na. From these results and the thermodynamic properties of this system, it is inferred that there forms a grouping of Na
4Pb in liquid Na–Pb alloys. The resistivity isotherm was analysed in terms of compound-forming effect.
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Setsuo Ichimaru, Hiroshi Iyetomi
1983 Volume 52 Issue 5 Pages
1730-1733
Published: May 15, 1983
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Local-field correction due to the exchange and correlation effects between electrons introduces the screening function for the electron-ion interaction different from that for the ion-ion interaction. The resulting corrections to the calculation of the electric resistivity are numerically investigated. It is found that the corrections are substantial in magnitude even at the electron density (
rs\simeq1) of relatively weak coupling.
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Giyuu Kido, Noboru Miura
1983 Volume 52 Issue 5 Pages
1734-1739
Published: May 15, 1983
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Magnetophonon resonance of high purity epitaxial
n-type GaAs was investigated in the configuration of
j⊥
B at various temperatures from 77 to 303 K using pulsed high magnetic fields up to 30 T. In the high magnetic field and low temperature region, a nonlinear increase of the amplitude againt the field was clearly observed in the resonant oscillation. A relation between the damping factor and the magnetic field was determined to be γ∝
B2⁄3 from our experiment, which suggests that the electron-phonon scattering is the dominant process for the damping at high magnetic field according to the Barker’s theory.
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Tsuneya Ando
1983 Volume 52 Issue 5 Pages
1740-1749
Published: May 15, 1983
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A computer simulation is performed to study localization of a two-dimensional electron system in strong magnetic fields. Scatterers with short-range δ-potentials are assumed, and the localization criterion based on the Thouless number
g(
L) is employed. It is shown that states are localized exponentially except in the vicinity of the center of each Landau level. The decay rate of the localized wave function, i.e., the inverse localization length, approaches zero smoothly at the center. This suggests that only the states just at the center of the Landau level are not localized and all the other states are exponentially localized, although the localization length is extremely large near the center. The energy range where the localization length is extremely large becomes wider with the Landau level index.
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Tomio Koyama, Sadamichi Maekawa, Masashi Tachiki
1983 Volume 52 Issue 5 Pages
1750-1758
Published: May 15, 1983
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Magnetization process in the mixed state of ferromagnetic superconductors is theoretically studied. By taking into account the electromagnetic and the s-f exchange interactions between conduction electrons and localized magnetic moments, the Ginzburg-Landau free energy is obtained. The polarization of localized magnetic moments depresses the stability of mixed state and causes a convex curvature in the magnetization versus magnetic field curve near the upper critical field
Hc2 above the ferromagnetic transition temperature. This curvature becomes larger with decreasing temperature, and the magnetization jump occurs at low temperatures. The characteristic features of magnetization process are in good agreement with those experimentally obtained by Crabtree
et al. in single crystals of ErRh
4B
4.
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Masaki Konno
1983 Volume 52 Issue 5 Pages
1759-1764
Published: May 15, 1983
Released on J-STAGE: June 01, 2007
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Invar alloy films with the fcc structure were prepared using the vacuum evaporation technique. Using the thickness graded film in the alloy compositions of 21%NiFe and 36%NiFe, the thickness dependence of saturation magnetization was studied. As the film thickness decreases from 1000 A to 200 A, the saturation magnetization of 36%NiFe decreases monotonically and that of 21%NiFe initially increases down to 350 A, and finally decreases. The temperature dependence of the saturation magnetization of 21%NiFe shows very flatter one compared with that of the theoretical Brilloin function.
These results are supposed to be origniated not from the existence of the gradient of the composition but from the appearance of γ
2 phase through the interface interraction between the substrate and film.
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Satoru Ohta, Akihiko Fujii, Shuichiro Anzai
1983 Volume 52 Issue 5 Pages
1765-1773
Published: May 15, 1983
Released on J-STAGE: June 01, 2007
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Magnetization and susceptibility are investigated on a solid solution between Cr
3Te
4 [a ferromagnetic (F) and canted ferromagnetic (CF) compound] and Rh
3Te
4 [a Pauli paramagnetic one]. The ferromagnetic Curie temperature
Tc decreases with increasing
y, while the transition temperature
Tt between CF and F phases increases. In the higher
y region, CF phase directly changes to the paramagnetic (P) phase at a transition temperature
TCF. The transition temperature
TCF decreases with increasing
y, and disappears at
y=0.47±0.02 and
T=55±15 K. An extra phase (Q) is found beyond CF one. Some characteristics of spin glass or mictomagnetic states are observed in Q phase. Between 0.29±0.03≤
y≤0.47±0.02, Q phase changes to CF one as the temperature increases. In the much higher
y region, Q phase directly changes to P one. These features, together with the anomalous
y-dependence of Weiss constant, are discussed on the competition between the negative and the positive exchange interactions.
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Koh Wada, Takuma Ishikawa
1983 Volume 52 Issue 5 Pages
1774-1780
Published: May 15, 1983
Released on J-STAGE: May 29, 2007
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Monte Carlo calculations have been used to study the spin ordering on a triangular Ising lattice with antiferromagnetic nearest neighbor and ferromagnetic next nearest neighbor couplings. It is suggested that a partially disordered antiferromagnetic phase does not occur stably because the sublattices interchange their roles among them due to lattice symmetry.
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Ikuo Nakai
1983 Volume 52 Issue 5 Pages
1781-1790
Published: May 15, 1983
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Detailed magnetization measurements for single crystals of Ni-rich Fe–Ni alloys have been carried out between 4.2 K and 300 K in external magnetic fields up to 16.9 kOe to a relative accuracy of 5×10
−5. It is found by iterative least-squares analysis of these observed values that the temperature variation of magnetization consists of two parts: one is due to the spin-wave excitations and the other due to the Stoner-type excitations. The coefficient of the latter part has a considerable value at pure Ni, decreases with addition of Fe atoms to pure Ni, vanishing around 70 at%Ni, and reappears at about 65 at%Ni. A simple picture for metallic ferromagnetism at finite temperatures is proposed.
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Ikuo Nakai, Fumihisa Ono, Osamu Yamada
1983 Volume 52 Issue 5 Pages
1791-1798
Published: May 15, 1983
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Precise measurements of magnetizations for single crystals of FCC Fe–Ni alloys in the Invar region have been made at temperatures from 4.2 K to 300 K in external applied fields up to 16.9 kOe to a relative accuracy of 5×10
−5. In an analysis of these observed results with iterative least-squares method, it is found that there exists a large Stoner-type contribution varying as
T2.00±0.05 besides the spin-wave one to the temperature change in magnetization and that the coefficient of the Stoner-type contribution increases rapidly with decreasing Ni concentration, showing a maximum at about 35 at%Ni, and decreases for the alloys containing less than 35 at%Ni. It becomes evident that ferromagnetism in FCC Fe–Ni alloys disappears at a critical concentration of about 31 at%Ni. An anomalous behavior of the magnetization at low temperatures is also shown.
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Hiroaki Kadowaki, Kinshiro Hirakawa, Koji Ubukoshi
1983 Volume 52 Issue 5 Pages
1799-1806
Published: May 15, 1983
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CsVCl
3 is composed of one-dimensional antiferromagnetic chains which are coupled weakly antiferromagnetically in the basal hexagonal plane. In order to clarify the anomalous properties hitherto observed, an inelastic neutron scattering has been studied. We observed good one-dimensionality of
J′⁄
J=2.7×10
−4. But, though
S=3⁄2, the spin wave dispersion along the chain disagrees with the classical picture. The excitation spectra along the triangular lattice plane are unusual. The excitation is dominated by a dispersionless mode of strong intensity. Compared to this mode, the conventional acoustic spin wave branch seems to be of minor excitation at lower temperatures than the Néel point.
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Tetsuya Sato, Makoto Sakata
1983 Volume 52 Issue 5 Pages
1807-1813
Published: May 15, 1983
Released on J-STAGE: June 01, 2007
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The magnetic susceptibility χ and the electrical resistivity ρ of CrGe and Cr
11Ge
8 are investigated at temperatures above 4.2 K. The magnetic susceptibility of CrGe exhibits a cusp at about 45 K and shows the
T2 dependence with positive coefficient at low temperatures. This behavior of CrGe, together with the behavior of ρ, is explained by the paramagnon theory for a nearly ferromagnetic metal. The reciprocal of χ of Cr
11Ge
8 deviates from the Curie-Weiss type relation at low temperatures, and ρ of Cr
11Ge
8 shows tendency of saturation at high temperatures. These behaviors of Cr
11Ge
8 are explained by the SCR theory for a nearly ferromagnetic metal. The magnetic and electrical properties of CrGe and Cr
11Ge
8 indicate that the natures of electron correlations of these compounds locate in the intermediate region between the Pauli paramagnet Cr
5Ge
3 and the ferromagnet Cr
11Ge
19.
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Kinshiro Hirakawa, Hiroaki Kadowaki, Koji Ubukoshi
1983 Volume 52 Issue 5 Pages
1814-1824
Published: May 15, 1983
Released on J-STAGE: May 29, 2007
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In order to study the frustration effects, we have taken powder diffraction patterns of VX
2, X≡Cl, Br and I) which are thought to be quasi-two-dimensional triangular lattice antiferromagnets. The spins in VCl
2, VBr
2 and VI
2 were found to order at 36.0, 29.5 and 16.3 K respectively forming a three sublattice structure in the basal plane. Contrary to our expectation, a partially ordered model gives a better fit to the observed diffraction rather than the Néel state with 120° structure though the spins are of Heisenberg symmetry. In VCl
2 and VBr
2, strong diffuse scattering can be observed not only at
T>
TN but also at
T<<
TN. No critical scattering characteristic for 2D could be seen but the temperature variation of sublattice magnetization is rather close to that for the Ising system.
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M. Umar, M. I. Haque, R. J. Singh
1983 Volume 52 Issue 5 Pages
1825-1828
Published: May 15, 1983
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Electron paramagnetic resonance of Cu
2+ ion in Sr(HCOO)
2·2H
2O were measured at room temperature. The spectrum was interpreted in terms of Jahn-Teller effect. Cu
2+ is found to be incorporated both interstitially and substitutionally. The substitutional Cu
2+ is found to be in nearly cubic environment and
Γ5 distortion is responsible for Jahn-Teller effect. The interstitial Cu
2+ finds itself in octahedral field which undergoes Jahn-Teller splitting due to
Γ3 coupling.
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Shin’ichi Katayama
1983 Volume 52 Issue 5 Pages
1829-1837
Published: May 15, 1983
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We present a theory of Raman scattering by the low-lying soft coupled plasmon-longitudinal optical (LO) phonon modes at low temperatures in semiconducting incipient ferroelectrics. The softening of this mode gives a dynamical intimation of the screened LO phonon instability induced by the displacive ferroelectric phase transition. We compare our calculations with Raman spectra from
n-KTaO
3 observed by Uwe
et al., on the basis of the soft mode-like behavior of the coupled modes as well as of the simple energy band structure.
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Takashi Kushida, Shuichi Kinoshita, Fumiaki Ueno, Tomoko Ohtsuki
1983 Volume 52 Issue 5 Pages
1838-1847
Published: May 15, 1983
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Transient behavior of secondary emission intensity has been measured near the fundamental absorption edge of ZnTe by means of a time-correlated single photon counting method under the excitation by subnanosecond light pulses from a CW mode-locked Ar
+ ion laser. The obtained time responses of bound-exciton luminescence lines, exciton-polariton luminescence bands and a Raman-like 2
LO line are analyzed. The dynamics of excitonic polaritons derived from the result are compared with a theoretical calculation, and the mechanisms of the appearance of the Raman-like
LO lines and the polariton luminescence bands are discussed.
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