-
Ken Sekimoto
1984 Volume 53 Issue 8 Pages
2425-2427
Published: August 15, 1984
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The exact space-correlation function is given of the two phase system for which the Avrami’s formula holds exactly. It is derived from the general standpoint of statistical geometry.
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Yukihiko Sasaki, Yoshio Takeuchi, Masakazu Marutake
1984 Volume 53 Issue 8 Pages
2428-2430
Published: August 15, 1984
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We have measured elastic compliance constants
sa,
sb and
sc for the elongation along the three crystallographic axes of the antiferroelectric CsH
3(SeO
3)
2 single crystal (triclinic, P\bar1) by the composite resonator method.
All the constants
sa,
sb and
sc have been found to exhibit large anomaly at the transition point (−128°C) and small anomaly near the temperature above it. This small anomaly suggests the existence of a new phase.
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Michio Midorikawa, Kazutoshi Gouhara, Yoshihiro Ishibashi
1984 Volume 53 Issue 8 Pages
2431-2433
Published: August 15, 1984
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Dielectric and dilatometric measurements were carried out to study the intermediate incommensurate phase of quartz crystal, which is stabilized between the α- and the β-phases. Anomalies associated with the transitions from the high temperature β-phase to the incommensurate phase and then to the α-phase were observed.
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Yukio Okwamoto
1984 Volume 53 Issue 8 Pages
2434-2436
Published: August 15, 1984
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An analytical study is made on a two-dimensional classical isotropic Heisenberg antiferromagnet in a uniform magnetic field. This model is expected to show the Kosterlitz-Thouless phase transition due to a XY-like degeneracy of a canted spin-flop ground state. It is shown that the transition temperature approaches zero logarithmically as the field approaches zero.
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Misuzu Watanabe, Kazuhiro Kaneda, Hiroyuki Takeda, Nobuo Tsuda
1984 Volume 53 Issue 8 Pages
2437-2440
Published: August 15, 1984
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An electrical conductivity and a thermopower of sintered Li
1.1Ti
1.9O
4 were measured. The Seebeck coefficient is proportional to temperature. The conductivity becomes larger with increasing temperature but it does not fit to the T
1⁄4 relation of a variable range hopping model nor to the relation for a small polaron hopping model at lower temperatures. To explain the transport, magnetic and thermal properties of Li
1+xTi
2−xO
4, it is proposed a bipolaron state in a random field.
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Kenji Makoshi, Hiroshi Kawai, Akio Yoshimori
1984 Volume 53 Issue 8 Pages
2441-2444
Published: August 15, 1984
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The effect of the intraatomic Coulomb interaction on the charge transfer is treated in the Hartree-Fock approximation with use of the time-dependent Anderson model which has been widely employed in gas-surface collision without the intraatomic interaction so far. The charge state of the scattered ion from the metal surface is calculated numerically for a case of simple time-dependence in a surface-adatom interaction within the wide band approximation. The total number of electrons transferred to the adatom-orbital is found to saturate in a rather short time interval. The spin polarisation grows exponentially, dependent on the spin splitting of the adatom level. Also shown is an oscillatory behaviour of spin polarisation near its equilibrium value after the exponential growth.
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K\={o}ki Takanashi, Hiroshi Yasuoka, Koyata Takahashi, Nobuyoshi Hosoi ...
1984 Volume 53 Issue 8 Pages
2445-2448
Published: August 15, 1984
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The interface magnetism of Co–Sb multilayered films with artificial superstructure has been studied from the
59Co NMR. The NMR signals from the nonmagnetic interface regions were successfully observed, distinctly separated from those from the ferromagnetic interior regions. The pattern of the spectrum suggests the possibility of the formation of a two-dimensional compound at the Co–Sb interface, where the local symmetry of Co atoms may have a similar structure as CoSb
2 or CoSb
3.
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Akihiko Sumiyama, Yasukage Oda, Hiroshi Nagano
1984 Volume 53 Issue 8 Pages
2449-2451
Published: August 15, 1984
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The Meissner effect of Au clad Nb wire has been measured using an ac Hartshorn bridge and a SQUID detector down to 15 mK. The thickness ρ of the Meissner region in Au induced by the proximity effect of Nb becomes larger as the temperature is decreased and almost the whole of the Au sheath shows the Meissner effect at lower temperatures. This effect is drastically suppressed by annealing the sample at about 600°C for a few minutes. The magnetic field dependence of ρ is also investigated. ρ is very sensitive to the magnetic field especially for the annealed sample.
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Hikaru Kawamura
1984 Volume 53 Issue 8 Pages
2452-2455
Published: August 15, 1984
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Lowest-order spin-wave analysis is applied to the antiferromagnetic plane rotator model on the triangular lattice in order to study the low-temperature properties in the presence of magnetic fields. Equilibrium spin configuration in the zero-temperature limit is calculated as a function of the magnetic field. It is found that the thermal-fluctuation effect reduces a continuous degeneracy of the ground state to a discrete one at non-zero temperatures.
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Kouichi Ishiyama, Akira Shinogi, Keizo Endo
1984 Volume 53 Issue 8 Pages
2456-2459
Published: August 15, 1984
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The temperature dependence of magnetic susceptibility, χ, of a cubic Laves phase compound ScCo
2 was measured in the temperature range 4.2–1018 K and found to have a broad maximum at about 600 K. The temperature dependent Knight shift,
K, of Sc was obtained from NMR experiment below room temperature. The
K vs χ plot gives a straight line resulting in −41 kOe/μ
B as a transferred hyperfine field from Co. It was concluded that ScCo
2 is an exchange enhanced Pauli paramagnet of the same kind of YCo
2 and LuCo
2.
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Yasuo Morimoto
1984 Volume 53 Issue 8 Pages
2460-2463
Published: August 15, 1984
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The properties of recurrence equation
X(
t+1)=
AX(
t)(1−
X(
t)−
X(
t−1)−
X(
t−2)) are investigated appearing in mutually connected nervous network having refractory period 3. The stable fixed point is 0 for
A<1 and (1−1⁄
A)⁄3 for 1≤
A<2.5. For 2.5≤
A<2.8 oscillation (or ultra long period periodic point) appears which shows critical behaviors. Usual analysis predicts instability at
A=3, which contradicts with numerical results. For 2.8<
A<2.85 chaos and window occur alternatively and large window from
A=2.85 to 2.9077. Above 2.9077 usual period-doubling bifurcation and chaos take place. The Lorenz plots of chaotic state have different structures below and above
A=2.9077.
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Shunji Kawamoto
1984 Volume 53 Issue 8 Pages
2465-2471
Published: August 15, 1984
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A cusp soliton solution, a usual soliton solution and periodic solutions to the normalized Boussinesq equation are obtained as stationary solutions. Also, the similarity equations are discussed as an integrability problem.
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Kazuaki Narita
1984 Volume 53 Issue 8 Pages
2472-2478
Published: August 15, 1984
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We discretize the wave equation with cubic nonlinearity along one of the two light-cone coordinates. The resultant semi-discrete equation exhibits discontinuous solutions in addition to the usual solitons. We interprete these as envelope solitons. We also discretize a complex wave equation with cubic nonlinearity and give its soliton solutions.
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Susumu Ohya, Katsuhiko Nishimura, Akira Furusawa, Naoshi Mutsuro
1984 Volume 53 Issue 8 Pages
2479-2484
Published: August 15, 1984
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175Ta and
177Ta nuclei were oriented at low temperature as dilute impurities in Fe. The magnetic hyperfine splitting frequencies ν=|μ
BHF⁄
Ih| of the
175Ta and
177Ta ground states have been measured to be 320.45(11) and 317.552(55) MHz by using the technique of NMR–ON. Taking the known hyperfine field of
181Ta in Fe, the magnetic moments have been deduced: |μ(
175Ta, 7⁄2
+)|=2.270(45) and |μ(
177Ta, 7⁄2
+)|=2.250(45) μ
N. These values of the magnetic moments are discussed in the framework of the rotational model.
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Jasbir Singh, M. L. Garg, Devinder Mehta, Nirmal Singh, P. N. Trehan
1984 Volume 53 Issue 8 Pages
2485-2490
Published: August 15, 1984
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The gamma-gamma directional correlation coefficients of 16 cascades in
160Dy following the decay of
160Tb (
t1⁄2=72.1 d) have been measured using a Ge(Li)–NaI(Tl) coincidence set-up (2τ≈6 n sec). Out of these, the correlation coefficients of the 310–962, 338–962, 392–(879)–87, 1003–(197)–87, 1103–(197)–87 and 1115–197 keV cascades have been measured for the first time. From these correlation measurements the spin value of 4
− has been confirmed for the 1386.5 keV level. The multipole mixing ratios of the 1003, 1103, 1115, 1200 and 1312 keV transitions in
160Dy have been determined for the first time.
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Osamu Sueoka, Shigeki Mori
1984 Volume 53 Issue 8 Pages
2491-2500
Published: August 15, 1984
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Total cross-sections for 1.0–400 eV positrons and 1.2–403 eV electrons colliding with N
2, CO and CO
2 molecules have been measured using a retarding potential-TOF technique. Results of positron-collisions for e
+-CO have shown clearly the Ramsauer-Townsend minimum. But the minimum was not shown clearly for e
+-N
2 and e
+-CO
2. These data were compared recent experimental data. Total cross-sections of electron-collisions were measured by the same technique for the comparison with those of positron-collisions, and they were compared with prior experimental data.
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Kiyoshi Ueda, Yoshihiro Hamaguchi, Takashi Fujimoto, Kuniya Fukuda
1984 Volume 53 Issue 8 Pages
2501-2505
Published: August 15, 1984
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Oscillator strengths have been determined for 23 transitions from the ground level of Ba relative to that of the resonance line by the hook method. The results are in good agreement with other experimental values. Rate coefficients of He-, Ar- and Kr-induced broadening have been measured for 6
s2 1S0-6
snp 1P1 (
n=7 to 10), 6
s2 1S0-5
dnp 1P1 (
n=6 and 7), and 6
s2 1S0-5
d7
p 3D1 and
3P1 by the total absorption method. We find that, generally, the rate coefficient increases monotonously to its maximum value and then decreases with the effective principal quantum number of the upper level relative to the first ionization limit. For 6
s2 1S0-5
d7
p 3P1 and
3D1, the rate coefficients deviate from this tendency and show minimum values. This singularity is explained qualitatively on the basis of the Fermi potential model by taking account of the configuration mixing.
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N. Riahi
1984 Volume 53 Issue 8 Pages
2506-2512
Published: August 15, 1984
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Nonlinear convection with spherically symmetric basic state is investigated in a thin spherical shell with rigid and nearly insulating boundaries. The nonlinear problem of steady three-dimensional convection is solved by a perturbation technique. Six physically distinct solutions are determined for the case where
l=5 (
l is the degree of spherical harmonics) is preferred. The preferred mode of convection is determined by a stability analysis. The axisymmetric solution is found to be unstable, while a non-axisymmetric solution which transports the maximum amount of heat appears to be preferred.
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Shin-ichiro Yanase, Michio Yamada
1984 Volume 53 Issue 8 Pages
2513-2520
Published: August 15, 1984
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The effect of the finite outer Rossby radius on two-dimensional isotropic turbulence in a single-layered fluid is investigated using the modified cumulant expansion method. This type of turbulence may be considered as a model of geostrophic turbulence in the atmosphere. The beta effect is neglected in order to avoid extra complexity.
It is found that turbulent motions with scale larger than the Rossby radius are strongly suppressed and consequently the inverse cascade of the energy is remarkably reduced. At large wavenumbers, the similarity law of the energy spectrum is identical to that of two-dimensional turbulence without rotation. The kinetic energy decreases in time, while the potential energy increases.
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Kanefusa Gotoh, David Y. Chung
1984 Volume 53 Issue 8 Pages
2521-2528
Published: August 15, 1984
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Experiments of ultrasonic attenuation have been performed in a water-based magnetic fluid by pulse-echo method. A box-car integrator was used to measure the change in attenuation due to an external magnetic field applied at various angles relative to the ultrasonic propagation vector. Complicated results were obtained when the attenuation was plotted as a function of the magnetic field strength and angles. So far no existing theoretical model gives satisfactory explanation for these results. In this paper, we attempted to derive expressions for the attenuation from the ferrohydrodynamical equations of Tarapov. Numerical calculations give fairly good agreement between the theory and the experiment with adjustable parameters.
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Shunjiro Ikezawa, Shuji Yamamoto, Susumu Takeda
1984 Volume 53 Issue 8 Pages
2529-2535
Published: August 15, 1984
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Electron contribution in the RF confinement of a mirror plasma by two cylindrical electrodes is reported. It is effective at a frequency corresponding to a parallel resonance including the electrode and the plasma. The plasma is sufficiently confined by a voltage of 40 volts, peak to peak, externaly applied to the plasma with an electron density
ne∼10
10 cm
−3 and an electron temperature
Te∼20 eV. The plugging force for the confinement is caused by the electric field
Ez parallel to the mirror axis, which produces the ponderomotive potential in electrons, and ions are confined by the ambipolar electric field. The measured distribution of the space potentials can explain well that the plasma is confined by RF field between two cylindrical electrodes.
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Katsuji Chiyoda
1984 Volume 53 Issue 8 Pages
2536-2538
Published: August 15, 1984
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A sufficient criterion for MHD stability is derived by use of the energy principle. This is a generalization of the criterion of Rosenbluth. The sufficient criterion is applied to a cylindrical plasma. It is also applied to a field-reversed configuration (FRC). It is found that the FRC considered here does not satisfy the criterion.
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Tadatsugu Hatori
1984 Volume 53 Issue 8 Pages
2539-2545
Published: August 15, 1984
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Similarity solutions for 2D MHD and 3D MHD turbulence are obtained assuming the invariance of the mean square magnetic potential and the magnetic helicity respectively in the limit of infinite Reynolds number. The temporal decay laws of the energy, the cross-helicity and the magnetic helicity are derived from these similarity solutions. The present conjecture concerning the decay process is discussed in comparison with the one employed by J. B. Taylor (1974).
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Keiichi Takasugi
1984 Volume 53 Issue 8 Pages
2546-2554
Published: August 15, 1984
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Potential formation is studied in Nagoya Bumpy Torus (NBT-1M) by the use of a heavy ion beam probe. The concentric negative potential well and its positive rim are observed in the standard operation. The position of the rim moves with the second harmonic ECRH zone at the midplane of each mirror section. It is confirmed that the core electron heating is essential for the potential well formation. A stable positive potential is observed near T–M transition with a smooth change from the negative profile.
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Noboru Yamada, Takuro Ikeda
1984 Volume 53 Issue 8 Pages
2555-2564
Published: August 15, 1984
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The modulated structure in the incommensurate phase of K
2SeO
4 has been analyzed at 113 K by X-ray diffractometry based on the concept of four-dimensional space. The final
R-factor was 0.046 for all 905 reflections and 0.087 for 326 satellite reflections.
The modulation is characterized by the rotation of SeO
4 groups around
b-direction and the associated translation of K atoms along
c-axis. The eigenvector of the modulation mode was determined from the observed atomic displacement pattern and it is compared with that of
Σ2 soft mode determined by neutron experiment.
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Noboru Yamada, Yasuhiro Ono, Takuro Ikeda
1984 Volume 53 Issue 8 Pages
2565-2574
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The crystal structure of K
2SeO
4 in the ferroelectric phase was analyzed and the structural change at the transition from incommensurate to ferroelectric phase was elucidated. The phase transition is characterized by a commensuration of structural modulation as well as an additional homogeneous structural change both in rotation of SeO
4 radicals around the
y-axis and in translation of K ions along the
z-axis. The spontaneous polarization in the ferroelectric phase is estimated on the basis of these structural changes and the contribution of the latter additional part is presumed to attain 60% or so. The symmetry coordinate components of
Σ2 soft mode were determined and the feature of atomic displacement responsible to this transition is discussed.
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O. P. Gupta
1984 Volume 53 Issue 8 Pages
2575-2583
Published: August 15, 1984
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Calculations of the phonon frequencies, temperature variation of Debye temperature, Grüneisen parameter, and electrical and thermal resistivities of cesium have been made using the modified form of our recent lattice dynamical model. An equilibrium condition, which preserves the crystal stability is obtained and incorporated with the model. The computed values are compared with the available theoretical and experimental data. Our theoretical results are in reasonably good agreement with the theoretical and experimental values.
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Takeo Ishidate, Shingo Katagiri, Kuon Inoue, Motoichi Shibuya, Kazuhik ...
1984 Volume 53 Issue 8 Pages
2584-2591
Published: August 15, 1984
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The alloying and pressure dependences of Raman spectra due to optic modes of lattice vibration in crystalline Si–Ge alloys have been measured. The effect of alloying on the mode frequencies is interpreted by introducing the heteropolar term due to the effective charge into the interatomic interaction as well as taking account of the bond lengths expected from the EXAFS measurements. The asymmetry of the observed Raman spectral-line shape is discussed on the basis of the structural disorder with deviations of the bond lengths.
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Hidehiko Sugimoto
1984 Volume 53 Issue 8 Pages
2592-2599
Published: August 15, 1984
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A formulation for the elastic energy of metal-hydrogen systems is derived by taking account of uniaxial components of strain in addition to dilatation, and a change of the self-trapped state with elongation of the
c axis is examined by solving the Schrödinger equation for a hydrogen isotope on interstitial sites in a bct lattice. From these calculations, it is shown that, in VH
0.5 and VD
0.5, the bct structure with an axial ratio
c⁄
a=1.1 is stabilized at low temperatures, with H(D) atoms occupying O
z sites.
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Hideyo Yoshida, Hiroaki Takemasa, Yasuo Oshino, Yasuharu Makita
1984 Volume 53 Issue 8 Pages
2600-2605
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The specific heat and thermal expansion of NH
4BeF
3 were measured. The crystal undergoes successive phase transitions at −22°C, 60°C and 253°C. The transition entropies were deduced from the data of the specific heat to be 0.66 cal/mol·deg for the phase transition at −22°C and 0.40 cal/mol·deg for the ferroelastic phase transition at 60°C, respectively.
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Hideyo Yoshida, Takeyo Tsukamoto, Hideo Futama, Yasuharu Makita
1984 Volume 53 Issue 8 Pages
2606-2612
Published: August 15, 1984
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The domain structures in ferroelastic NH
4BeF
3 were observed and examined with a polarizing microscope both in the presence and absence of relevant external stresses. The crystal exhibits domain structures with a group of (100), (010), (001), (10
n), (10\bar
n) (
n=2.06) walls and another group of the (101) and (10\bar1) walls. Only the domain structures of the first group disappear above the ferroelastic phase transition point of about 60°C. The crystal is triclinic at room temperature and orthorhombic at 80°C. It is shown that all the observed domain structures of the first and second groups can be deduced from the strain-compatibility condition by taking account of the symmetry change from mm2 to 1 associated with the ferroelastic phase transition at 60°C and a symmetry change associated with a hypothetical hexagonal-orthorhombic phase transition, respectively.
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Yukio Okwamoto
1984 Volume 53 Issue 8 Pages
2613-2621
Published: August 15, 1984
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A study is made on a two-dimensional classical XY model with anisotropic coupling yielding a helical ground state. Two phase transition temperatures are estimated in the neighborhood of the Lifshitz point by examining the stability of the helimagnetic phase against formation of vortices and domain walls between regions of opposing chirality of the helical state. These temperatures are different from those obtained by Garel and Doniach.
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Tadao Ishii
1984 Volume 53 Issue 8 Pages
2622-2628
Published: August 15, 1984
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The lowest eigenvalue of the transfer-integral equation for the Frenkel-Kontorowa system, having the misfit parameter
l (closely related to a normalized particle density ρ), and the specific heat derived therefrom are analytically discussed from a high-temperature expansion approach. In the case of
l=0 (ρ=1) for which Schneider-Stoll [SS] have obtained exact numerical solutions, we can reproduce a maximum of the specific heat about 1.06 at
kBT=11.0 in SS units, being passably consistent with the SS exact result. The cases for
l≠0 (1>ρ>0.5) are also studied together with a validity range of the present approximation.
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Jun-ichi Igarashi
1984 Volume 53 Issue 8 Pages
2629-2639
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A theoretical study is presented of the spherically symmetric phase (SP) of solid orthodeuterium at high pressure, where the processes making one roton split into two and three ones are taken into account. The Raman spectra due to rotational excitations are calculated, where the width of three peaks in the spectra becomes broad with increasing pressure in good agreement with the experiment by Silvera and Wijngaarden. The transition from the SP to the phase of broken symmetry is studied by taking account of the correlation energy. A rapid shift of the frequency of vibron (intramolecular-vibrational excitation) is predicted to occur in the close vicinity of transition pressure.
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Fusayoshi J. Ohkawa, Hidetoshi Fukuyama
1984 Volume 53 Issue 8 Pages
2640-2650
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Magnetoresistance through an interplay between the Kondo effect and the Anderson localization is investigated in the weakly localized regime. The anomalous resistivity in the order of
J3, which is in proportion to
Td⁄2−2 in the absence of magnetic fields, is seen to be suppressed, once the Zeeman energy exceeds the thermal energy;
J,
T and
d are an exchange interaction constant, temperature and dimensionality, respectively.
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Yoshimasa Kumashiro, Kazutaka Tsuji, Shuzo Takano
1984 Volume 53 Issue 8 Pages
2651-2658
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Effects of In-impurity on the electrical properties of an In-doped n-type Pb
1−xGe
xTe (
x=0.02) are investigated between 4.2 K and 300 K. It is found that the Hall coefficient shows the qualitatively similar anomalous behaviour to that of In-doped PbTe. But, the resistivity increased almost exponentially with increasing temperature. The phase transition is not affected by In-doping. The energy spectrum in the rhombohedral phase is studied by observing the quantum oscillations of the sound velocity at 1.5 K. It is found that the angular dependences of the observed periods are well fitted to the model which has been proved to be valid for undoped Pb
1−xGe
xTe in our previous work.
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Nobuyoshi Hosoito, Kenji Kawaguchi, Teruya Shinjo, Toshio Takada, Yasu ...
1984 Volume 53 Issue 8 Pages
2659-2667
Published: August 15, 1984
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Multilayered films with artificial superstructures were synthesized by alternate deposition of Fe and V in ultrahigh vacuum. X-ray diffraction confirmed the establishment of artificial periodicities with very short wavelengths,
e. g. Fe(4Å)–V(8 Å) of the minimum case, and bcc [110] texture. Magnetic properties as a function of Fe layer thickness were studied from Mössbauer and SQUID measurements.
Local magnetization at the Fe interface layer contacting with V is discussed from Mössbauer results on surface-selectively enriched samples and also from polarized neutron diffraction experiments.
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Takao Itoh, Koichi Kitazawa, Shoji Tanaka
1984 Volume 53 Issue 8 Pages
2668-2673
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Specific heat coefficient of BaPb
1−xBi
xO
3 at low temperatures was measured by the thermal relaxation method. Although the discontinuity in the specific heat
C at the superconducting transition temperature
Tc could not be detected, it was clearly observed in the lowest experimental temperature region that
C in the superconducting state at zero magnetic field was smaller than in the normal state at
H=59 kOe. The electronic specific heat coefficient γ increased with
x until
x=0.25 and then decreased above, corresponding to the composition dependence of
Tc. However, the γ value,
e.g. 1.6 mJ mole
−1K
−2 at
x=0.25, was one to two orders of magnitude smaller than those of the other typical high
Tc superconducting metals. The Debye temperature was in the range 166 K to 196 K for 0≤
x≤0.3.
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Koh-ichi Ueda, Yoshio Kitaoka, Yoh Kohori, Takao Kohara, Kunisuke Asay ...
1984 Volume 53 Issue 8 Pages
2674-2680
Published: August 15, 1984
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Pulsed NMR studies of
59Co and
11B have been performed in a series of antiferromagnetic RECo
4B
4 compounds (RE=Gd, Tb, Ho, Er, Tm) in both paramagnetic and magnetically ordered states. In the paramagnetic state, NMR signals of both
59Co and
11B were observed only in GdCo
4B
4 in the temperature range of 77–300 K. From the isotropic Knight shift measurement, we obtained the conduction electron spin polarization at both Co and B sites generated by the
d-
f exchange interaction on the rare earth site. The electron spin polarization estimated in RECo
4B
4 is about twice as large as that in RERh
4B
4 system. In the antiferromagnetic state, zero-field resonances of
59Co and
11B were observed for GdCo
4B
4, TbCo
4B
4 and DyCo
4B
4 at 1.3 K. From the hyperfine fields and NMR spectra, the spin structure is shown to be the same type as in the antiferromagnetic superconductor Ho(Rh
0.3Ir
0.7)
4B
4.
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Sadamichi Maekawa, Hiromichi Ebisawa, Hidetoshi Fukuyama
1984 Volume 53 Issue 8 Pages
2681-2687
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The superconducting transition temperature
Tc and upper critical field
Hc2 in dirty superconductors are studied by taking into account the dynamically screened Coulomb interaction and disorder, perturbatively. We find that the results depend on the relative magnitude of τ
0−1 and ω
D, τ
0 and ω
D being the relaxation time of an electron and the phonon-Debye frequency, respectively, even in the weakly localized regime. We examine the case of τ
0−1<ω
D exclusively in this paper. The Anderson localization enhances the Coulomb repulsion between electrons and modifies the density of states. In addition, disorder induces the depairing effect due to the retardation of the Coulomb interaction. We obtain that
Tc decreases in proportion to the sheet resistance in thin films and to λ
2 in bulk systems where λ=h⁄2πε
Fτ
0, ε
F being the Fermi energy. The correction in
Tc is a function of |ln
Tcτ
0| in both bulk systems and thin films.
View full abstract
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Satoru Funahashi, Jun Akimitsu, Kiiti Siratori, Noboru Kimizuka, Midor ...
1984 Volume 53 Issue 8 Pages
2688-2696
Published: August 15, 1984
Released on J-STAGE: June 01, 2007
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Neutron and X-ray diffraction studies were carried out on polycrystalline specimens of stoichiometric (S-) and non-stoichiometric (N-) YFe
2O
4. An asymmetric diffraction line was observed above the Néel point (
TN\simeq235 K) in S-YFe
2O
4 and both above and below
TN (
TN\simeq210 K) in N-YFe
2O
4. At above
TN, the line profile was quantitatively interpreted as due to two-dimensional critical scattering, on an assumption that the scattering cross section is a Lorentzian in a
h-
k plane, independent of
l. The correlation length, κ, and the susceptibility at (1/3, 1/3,
l), χ, obey an exponential law: κ∝(
T−
TN′)
ν and χ∝(
T−
TN′)
−γ, respectively, with ν=1.5±0.05, γ=3.1±0.1 and
TN′=233.0±0.5 K in S-YFe
2O
4. It was concluded that the spin correlation is two-dimensional in the hexagonal YFe
2O
4, both in the S- and N-compounds, but a crystal deformation induces a three-dimensional spin ordering in S-YFe
2O
4.
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Fusayoshi J. Ohkawa
1984 Volume 53 Issue 8 Pages
2697-2702
Published: August 15, 1984
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The density function theorem is proven that there is a unique one-to-one correspondence at the absolute zero temperature between the density of
f electrons and the depth of
f levels. The ground state properties such as the Kondo temperature, and the charge and spin susceptibilities are calculated for infinitely large Coulomb correlation, and they are expressed in terms of the density instead of the depth. An application to a lattice Anderson Hamiltonian (or the dense Kondo state) is briefly discussed; the correction due to nearly empty excited
f multiplets is small enough to be ignored in the critical number of occupied
f electrons for the realization of the dense Kondo state; the critical number is very close to unity.
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Shunya Abe, Takejiro Kaneko, Masayoshi Ohashi, Hajime Yoshida, Kazuo K ...
1984 Volume 53 Issue 8 Pages
2703-2709
Published: August 15, 1984
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It is experimentally known that an antiferromagnetic compound CrSb (
TN≅700 K) with a NiAs type crystal structure exhibits unusual magnetic properties, that is, sharp decrease of magnetic moment, steep increase of magnetic specific heat and of magnetic susceptibility just below
TN with increasing temperature. These unusual behaviours are discussed on the basis of a molecular field theory by taking into account anisotropic strain dependence of exchange interactions. And it is pointed out that an effect of anisotropic normal thermal expansion of the crystal lattice can not be neglected.
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Mitsuhiro Motokawa, Takaaki Harada, Toshiro Sakakibara, Muneyuki Date, ...
1984 Volume 53 Issue 8 Pages
2710-2717
Published: August 15, 1984
Released on J-STAGE: May 29, 2007
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Magnetization measurements of Rb
2Co
xMg
1−xF
4 (
x=0.91, 0.82, 0.75, 0.70, 0.60, 0.30), which is a two-dimensional random Ising spin system, have been performed by pulsed high magnetic field up to 500 kOe. The abrupt magnetization changes at 190 kOe and 380 kOe, which are independent of concentration, are due to the exchangeflips of spins with 1 and 2 nearest neighbor Co
2+ spins, respectively. Another change, whose field depends on the concentration, is ascribed to the order-disorder transition similar to that observed in three-dimensional Fe
xZn
1−xF
2. The temperature dependence of this transition field is also measured for
x=0.82 and 0.75 up to the Néel temperature and phase diagrams are obtained. The Néel temperatures determined from this experiment are 68 and 60 K, respectively.
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Shoji Ishida, Setsuro Asano, Junji Ishida
1984 Volume 53 Issue 8 Pages
2718-2725
Published: August 15, 1984
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The bandstructures were calculated by the local-spin-density (LSD) method for the alloys Cu
2MnAl, Ni
2MnSn, Pd
2MnSn, Pd
2MnSb, Co
2MnSn, Co
2TiSn, Co
2TiAl and Mn
2VAl. We calculated the magnetic moments and the hyperfine fields for these alloys on the basis of the bandstructures. The peak near the Fermi level of the density-of-states (DOS) curve is characteristic for Co in Co
2YZ and plays an important role in determining the magnetic moment and the hyperfine field. For Mn
2VAl, the magnetic moments on Mn and V are antiparallel. Roughly speaking, the calculated hyperfine fields are in good agreement with the experimental ones. However, we evaluate the contribution to the hyperfine field from inner core
s-electrons small when we use the LSD method.
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Yoshikazu Ishikawa, Masatoshi Arai
1984 Volume 53 Issue 8 Pages
2726-2733
Published: August 15, 1984
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The magnetic phase diagram of MnSi near the critical temperature
TN=29.5 K has been studied by neutron small angle scattering at KENS. It has been found that the anomalous new phase predicted by various methods to exist around at 28 K and 2 kOe is the paramagnetic phase where the magnetic correlations exhibit the same characteristics as those found at 29.5 K and zero magnetic field. This phenomenon, together with the sharp decrease of the magnetic phase boundary at
TN and the substantial increase of the satellite
Q vector at this temperature, has been found not to be interpreted by the current theories.
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Yoshichika \={O}nuki, Yasunori Furukawa, Takemi Komatsubara
1984 Volume 53 Issue 8 Pages
2734-2740
Published: August 15, 1984
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We have measured the electrical resistivity and the magnetic susceptibility of Ce
xLa
1−xAl
2 (
x=0–1) single crystals to study the dense Kondo phenomenon. The magnetic resistivities per molar cerium, which result from the combined effect of the crystalline field and the Kondo scattering, are found to be almost the same at higher temperatures than ca. 50 K. The Curie temperature of ca. 30 K and the effective Bohr magneton of ca. 2.5 μ
B are also independent of the concentration of cerium ion. These data show that the dilute Kondo state is continuously connected to the dense Kondo state as a linear function of cerium concentration in the paramagnetic region.
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Kazuyoshi Ichinose, Katsuyuki Fujiwara, Hiroshi Yoshie, Hiroyuki Nagai ...
1984 Volume 53 Issue 8 Pages
2741-2744
Published: August 15, 1984
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Nuclear magnetic resonance of
27Al nuclei in (Gd
1−xDy
x)Al
2 compounds at 4.2 K has been observed for 0≤
x≤1. The spectra of these compounds have two peaks for 0≤
x≤0.3 and single peak for 0.4≤
x≤1. The results show that the direction of the gadolinium moment changes from the [111] to [100] direction around
x\simeq0.3. The experimental results have been explained by rotation of the dipole field.
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Masatsugu Suzuki, Kei-ichi Koga, Yoshinobu Jinzaki
1984 Volume 53 Issue 8 Pages
2745-2751
Published: August 15, 1984
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ESR measurements have been made at 9 GHz in the temperature range 4.2 K≤
T≤300 K, on the second-stage NiCl
2-graphite intercalation compound based on a single crystal of Kish graphite, which approximates to an ideal two-dimensional ferromagnet in the presence of an external magnetic field. The angular and temperature dependences of the ESR resonance field and line-width show that the spin symmetry of this system changes from XY-like to Heisenberg-like at ∼
Tg (≅30 K) as the temperature increases. The experimental results on ESR at sufficiently high temperatures above
Tg are qualitatively explained in terms of the magnetic behaviour of the two-dimensional Heisenberg-like ferromagnet.
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Kunihiko Morimoto, Kenji Shimomura
1984 Volume 53 Issue 8 Pages
2752-2760
Published: August 15, 1984
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Proton spin-lattice relaxation time
T1ρ in the rotating frame was measured in ammonium sulfate between 370 K and 118 K. The minimum value of
T1ρ (2∼4 sec) in the paraelectric phase of ammonium sulfate is attributed to the reorientation of SO
4−2 which modulates the dipolar interaction between
1H and the natural abundance of
17O spins (0.037%) and not the effect of the ferroelectric mode proposed by Knispel
et al. and Nordland
et al. The activation energy
Ea∼4 kcal/mol for the reorientation of SO
4−2 was determined.
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