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Atsunori Danjo, Atsushi Matsumoto, Shunsuke Ohtani, Hirosi Suzuki, Hir ...
1984 Volume 53 Issue 12 Pages
4091-4093
Published: December 15, 1984
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Absolute cross sections for electron impact single ionization of doubly charged rare gas ions, Ne
2+, Ar
2+, Kr
2+ and Xe
2+, have been measured in the energy range from below threshold to 1000 eV. The measurements were performed with crossed electron and ion beam technique. The measured cross sections for Ne
2+ ions are found to be in good agreement with the semiempirical Lotz formula for direct ionization. For Ar
2+ ions is found a small discrepancy between the observed cross section and the formula at lower energies. For Kr
2+ and Xe
2+ ions the measured cross sections exhibit complicated structures from threshold to medium energy and are significantly larger than estimates for the direct ionization. These enhancements and complex structures are believed to be indirect ionization processes, such as excitation-autoionization.
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Kiyoshi Yamamoto
1984 Volume 53 Issue 12 Pages
4094-4097
Published: December 15, 1984
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Two-dimensional Navier-Stokes turbulence at very high Reynolds numbers is numerically investigated by the use of spectral method. The energy spectrum obtained here reveals almost the theoretically predicted
k−3 law in the inertial subrange at Reynolds numbers 5000 and 10000, while giving the
k−4 law at Reynolds number 1000 in agreement with the results of all the so far known numerical work.
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Fukuo Yoshida
1984 Volume 53 Issue 12 Pages
4098-4101
Published: December 15, 1984
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Dynamical properties of super-cooled liquids are studied in the intermediate wavenumber region. A polarization function is shown to describe the relaxation of the structure sustaining effective potentials. Effects of its slow relaxation are discussed on the dynamical structure factor as well as the transverse current correlation function for liquid argon.
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Ikuo Ono
1984 Volume 53 Issue 12 Pages
4102-4105
Published: December 15, 1984
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Monte Carlo simulations of three-state Potts models interacting with nearest-neighbor antiferromagnetic
J1 (<0) and next-nearest-neighbor ferromagnetic
J2 (>0) are carried out on a square lattice. At enough low temperatures an antiferromagnetic ordering is shown to appear except for
J2=0. In the intermediate temperatures the occurrence of the Kosterlitz-Thouless-like phase is indicated from the estimation of the critical exponent η.
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Hideoki Kadomatsu, Takanori Tsutaoka, Hiroshi Fujiwara
1984 Volume 53 Issue 12 Pages
4106-4108
Published: December 15, 1984
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The thermal expansion of Eu
xYb
1−x alloy was measured in the temperature range from 4.2 K to 80 K. Invar type anomaly was observed for
x=0.1 and 0.2. The minimum values of the thermal expansion coefficient for
x=0.1 and 0.2 were −7×10
−5 K
−1 and −6×10
−5 K
−1, respectively.
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Kichizo Asai, Fumitoshi Ambe, Shizuko Ambe, Hisashi Sekizawa
1984 Volume 53 Issue 12 Pages
4109-4112
Published: December 15, 1984
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Time differential perturbed angular correlation (TDPAC) of γ-rays emitted from
111Cd(←
111In) doped in α-Fe
2O
3 was measured. The spectrum observed at 420°C was analyzed well with a unique set of a hyperfine magnetic field and an electric field gradient. Conversely, the one observed at 20°C was analyzable only by introducing a distribution to a certain hyperfine parameter because of the after-effects of the preceding EC decay. Electric field gradient for the excited ions after the EC decay seems to be somewhat different from that for the stable ions. The disappearance of the after-effects at 420°C means that the strongly temperature dependent lifetime of the excited ions is very short at this temperature. The present results show that TDPAC using nuclides arising from EC decays can be useful in studying insulators by making a high temperature measurement.
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Midori Tanaka, Kiiti Siratori, Noboru Kimizuka
1984 Volume 53 Issue 12 Pages
4113-4116
Published: December 15, 1984
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Mössbauer spectra of
57Fe in RFeMO
4, a family of triangular antiferromagnets, were observed below 300 K, mainly at 4.2 K. For the compounds of M=Mn or Co, it was concluded from the spectra at 4.2 K that the axis of the electron spin of Fe
3+ is not determined as related with the crystal lattice but distributes homogeneously. The spin state was discussed briefly in connection with the recent theoretical work on the antiferromagnetic triangular lattice.
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Akira Shinogi, Keizo Endo, Yoshio Kitaoka, Hiroshi Yasuoka
1984 Volume 53 Issue 12 Pages
4117-4120
Published: December 15, 1984
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The magnetic susceptibility of CsCl-type CoTi was expressed as the Curie-Weiss susceptibility plus temperature independent term at temperatures above about 300 K, i.e. 1637⁄(
T+6.66)+3.92 in the unit of 10
−4 emu/mol. In the same temperature range, the d spin component of the relaxation rate associated with the
59Co nuclei showed saturation from the low temperature Korringa process. From the analysis of the d-spin relaxation, it is concluded that the amplitudes of the temperature dependent spin density fluctuations are saturated above
T*=300 K and behave as if local moments are induced.
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Yoshiyuki Takayama, Kiyoshi Deguchi, Eiji Nakamura
1984 Volume 53 Issue 12 Pages
4121-4124
Published: December 15, 1984
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Dielectric dispersion of triglycine sulfate in the vicinity of the Curie temperature
Tc was observed in the frequency range from 1 kHz to 1 GHz. The relaxation time τ of the dispersion is well expressed by the power law τ∝(
T−
Tc)
−Δ in the region 0.07 K\lesssim
T−
Tc\lesssim10 K with
Δ=1.07 that is quite different from the non-classical value,
Δ\simeq2⁄3, reported recently. The magnitude of the activation energy of dipole reversal is found to be about 3
kTc, which is fairly larger than that in the earlier study, indicating that the phase transition is of the order-disorder type.
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Yasukazu Yoshizawa, Shinji Nakanoda, Yasuhiro Kawabata, Eiichi Tanaka, ...
1984 Volume 53 Issue 12 Pages
4125-4128
Published: December 15, 1984
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Energies of positron annihilation radiation from various materials were measured with Ge detectors. Energies of annihilation radiation are clearly smaller than the electron rest mass. The Compton wavelength and the rest mass of electrons were determined to be 2.426310(15) pm and 511003.1±3.2 eV, respectively, with correction of the positronium binding energy by using annihilation radiation from ice. For other cases the differences are attributed to the minimum potentials of positrons in material as well as the binding energies of electrons. However, the differences are deviated from the expected values.
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Walter Strampp
1984 Volume 53 Issue 12 Pages
4129-4137
Published: December 15, 1984
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In this paper we study interrelations between the Lax-formulation, Bäcklund transformations and recursion operators. It is shown that different integrability conditions can be connected via Lie-Bäcklund symmetries of the Lax-formulation. This is then used to derive Bäcklund transformations and recursion operators for various equations.
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Hikaru Kawamura, Seiji Miyashita
1984 Volume 53 Issue 12 Pages
4138-4154
Published: December 15, 1984
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Ordering process of the antiferromagnetic Heisenberg model on the two-dimensional triangular lattice is studied both by topological analysis of defects and by Monte Carlo simulation. It is shown that the order parameter space of this model is isomorphic to the three-dimensional rotation group SO(3) due to the inherent frustration effect. Homotopy analysis shows that the system bears a topologically stable point defect characterized by a two-valued topological quantum number and exhibits a phase transition driven by the dissociation of the vortices. A Monte Carlo study on the specific heat and the behavior of vortices strongly suggests the occurence of a Kosterlitz-Thouless-type phase transition. It is, however, argued that in contrast to the two-dimensional
XY model, the spin-correlation function decays exponentially even in the low-temperature phase. In order to distinguish the high- and low-temperature phases qualitatively, we introduce a “vorticity function” analogously to the Wilson loop in the quark-confinement problem in the lattice gauge theory. A discussion is made on possible interpretations of the experimental data for triangular lattice Heisenberg antiferromagnets.
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T. P. Pandya, L. M. Bali, Ms. Usha Bakshi, A. K. Singh
1984 Volume 53 Issue 12 Pages
4155-4157
Published: December 15, 1984
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A covariant formulation of the single particle dynamics in free electron laser is presented. The equations of motion are solved to obtain an expression for gain upto the fourth order. The theory puts Colson’s approximation scheme in a clearer perspective and indicates decrease in laser gain at high power densities.
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Takashi Inoue
1984 Volume 53 Issue 12 Pages
4158-4168
Published: December 15, 1984
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Excitation functions and angular distributions of the
19F(p, α
i)
16O reactions have been measured in the energy range
Ep=4.15–13.0 MeV. The results were analysed by the statistical model. Correlation analyses were made to investigate resonance-like structures. No marked correlations between different channels were found. The DWBA calculations were made to interpret a backward rise which appeared in the α
0 channel.
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N. Riahi
1984 Volume 53 Issue 12 Pages
4169-4178
Published: December 15, 1984
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The problem of thermal convection is studied in a horizontal layer of fluid with an internal heat source which is restricted to vary linearly with the vertical variable. Square and hexagonal cells are found to be the only possible stable convection cells. Finite amplitude instability can occur for a range of the amplitude of convection. The presence of internal heating is found to be able to affect strongly the cell’s size, the critical Rayleigh number, the heat transported by convection, the stability of the convective motion and the internal motion of the hexagonal cells.
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Yasutomo Ohguchi
1984 Volume 53 Issue 12 Pages
4179-4183
Published: December 15, 1984
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It is known that thermal conductivity of hydrogen gas over 4500 K derived from theories much deviates from conductivity determined through experiments. This paper points out that the conductivity determined by experiments is not directly measured, and that the method is inconsistent. The inconsistency results from the use of Elenbaas-Heller equation despite of strong nonequilibrium of the used arc plasmas. The real thermal conductivity is estimated through examinations of temperature profiles and
E-
I characteristics derived from the two-temperature theory and those measured by Steinberger. It is reasonable that the real thermal conductivity lies between two curves obtained by theories and by experiments.
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Ken Adachi, Ryuji Takaki
1984 Volume 53 Issue 12 Pages
4184-4191
Published: December 15, 1984
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Vibration of a single drop of liquid nitrogen, oxygen or argon was observed by putting it on a horizontal plate with the room temperature. The drop had a shape of flattened disk and floated on the plate owing to rapid evaporation. It showed a characteristic mode of vibration, namely a standing wave appeared along the periphery and the plane view showed a polygonal shape. As the radius of drop reduced through evaporation, sudden transitions to modes with smaller number of vertices occurred. The measured vibrational frequency was proportional to (wave number)
3⁄2, and depended in a simple way on the surface tension and the density of the liquid.
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Katsuhisa Koura
1984 Volume 53 Issue 12 Pages
4192-4199
Published: December 15, 1984
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The isotope effects of H
2 and D
2 on the thermalization of epithermal electrons in gases are studied with the Monte Carlo simulation using the experimental cross sections. The influence of the gas temperature
T on the isotope effects is examined at
T=300 K, 77 K [∼θ
r(H
2)], and 40 K [∼θ
r(D
2)], because the characteristic rotational temperature θ
r corresponds to the rotational threshold. The electron velocity distribution deviates significantly from the local Maxwell distribution (MD) in both H
2 and D
2; consequently the degradation of the effective electron temperature
Te is slower than that obtained with the MD assumption. The electron thermalization time τ
th when
Te⁄
T=1.1 is larger than that for the MD to the extent of 290% in D
2 at
T=40 K. The isotope effect is most prominent for the pressure normalized thermalization time τ
thp at
T=77 K [τ
thp(D
2)⁄τ
thp(H
2)=0.35] because θ
r(H
2)\gtrsim
T>θ
r(D
2).
Te and τ
thp are compared with those calculated from available experimental energy exchange rate coefficients.
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Yoshiomi Kondoh
1984 Volume 53 Issue 12 Pages
4200-4209
Published: December 15, 1984
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A hybrid plama diode model with rapid current expansion is proposed for charged particle accelerations in the plasma focus discharge. It is shown that the model leads to strong induced electric fields sufficient for MeV order accelerations with a short acceleration time less than or around 1 nsec and a short acceleration length around 1 mm. A simple scaling for resultant energies of charged particles by the model is discussed and compared with results of a simulation of the plasma focus discharge. A possibility of connection of the model with one of the origins of cosmic rays is discussed.
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Nagao Kamijo, Kichiro Koto, Yoshiaki Ito, Hironobu Maeda, Kazuhiro Tan ...
1984 Volume 53 Issue 12 Pages
4210-4220
Published: December 15, 1984
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Extended X-ray absorption fine structure (EXAFS) studies are carried out for fluorites, β-PbF
2 (at 80 K, 293 K and 640 K) and SrF
2 (at 293 K and 640 K) to investigate their ion conduction mechanism of anion. In β-PbF
2 it is found that fluorine ion does not occupy only the center of the Pb tetrahedron site but displaces along 〈111〉 into several separate sites even at 80 K and this tendency is remarkably increased as temperature increased up to its transition temperature. In SrF
2 it is found that fluorine ion also displaces along 〈111〉 but is smaller in quatity at the same temperature as compared with β-PbF
2. These interstitial anions play a key role in ion conduction process indicating that hopping model of anion is probable.
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Kotaro Ono, Takao Kino
1984 Volume 53 Issue 12 Pages
4221-4229
Published: December 15, 1984
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A thermal generation kinetics from faulted loops in high purity aluminum has been studied by the pulse heating technique and the residual resistance measurement. The average concentration of vacancies generated from the loops exceeds the thermal equilibrium concentration of vacancies at the pulsing temperature, depending on the size of the loop. Such a generation profile is explained by a generation mechanism which is promoted by the line tension of the faulted loop. The characteristic promotive energy
ΔE in this process is derived to be 0.018 eV and 0.038 eV for the loops with the average diameter 75 nm and 40 nm, respectively. It is concluded that the significant part of
ΔE is due to the elastic energy change of the loop associated with the emission of a vacancy, and that the contribution from the stacking fault to
ΔE is small in contrast to the earlier works in aluminum.
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Yoshio Saito
1984 Volume 53 Issue 12 Pages
4230-4240
Published: December 15, 1984
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Structural studies on vacuum-deposited amorphous Ge films have been carried out by high resolution electron microscopy using an axial beam illumination. Crossed lattice images are observed in the films, which show that the amorphous films consist of micro-crystallites. The micro-crystallite size is about 14 A in diameter. It is shown that the 14 A micro-crystallite has a minimum value of the surface energy. An oriented and a distorted micro-crystallite models based on the diamond structure are proposed for the amorphous Ge and Si. The distorted micro-crystallite model interprets the diffraction intensity over the wide scattering angle, much better than any model that has ever been reported.
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Yukio Noda, Shinji Nishihara, Yasusada Yamada
1984 Volume 53 Issue 12 Pages
4241-4249
Published: December 15, 1984
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Time resolved X-ray scattering experiments have been carried out to investigate the kinetics of configurational ordering process in Cu
3Au alloy in the vicinity of its order-disorder phase transition point. In the later stage of the ordering process, we observe that the X-ray diffraction profiles show universal scaling property in terms of space and time; when reciprocal space and time are scaled properly, the observed diffraction spectra give a common functional form irrespective of the quench depth. The experimental scaling function is expressed simply by a squared Lorentzian curve. It is also seen that the critical droplet size and the incubation time which give the scaling parameters with respect to space and time critically diverge as the quench depth is reduced to zero.
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Yoshihiro Ishibashi, Ikuo Suzuki
1984 Volume 53 Issue 12 Pages
4250-4256
Published: December 15, 1984
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The functional form of the thickness dependence of the pinning energy of kinks due to discreteness of substrate lattices is discussed by using the contour integral method. It is shown that the functional form can be guessed without knowing the energy distribution as a function of coordinate. The relative stability of the kinks of the odd and the even types may be sometimes reversed according to the parameter values describing the substrate potential. The result previously reported for a nonlinear deformable potential is interpreted. The contour integral method is applied to calculate the pinning energy of the double quadratic kinks.
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Kunihiko Yamaguchi, Yuichiro Nishina
1984 Volume 53 Issue 12 Pages
4257-4265
Published: December 15, 1984
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The mode behaviors of the zone-edge phonons in the pseudo-binary layer-type semiconductor GaS
xSe
1−x (0≤
x≤1) have been analyzed in terms of the inelastic electron tunneling (IET) spectra in Pb-GaS
xSe
1−x-Pb junctions. The IET spectral peaks correspond to those phonon energies with their extrema in the density of states at the zone-edges. The
x-dependence of the phonon energy thus determined indicates that most of these phonons exhibit two-mode behaviors.
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J. Houard, A. A. Gomes
1984 Volume 53 Issue 12 Pages
4266-4270
Published: December 15, 1984
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A quenched disordered system A
1−cB
c possessing an easy magnetization plane and exhibiting competing exchange and anisotropy is studied by means of a Monte Carlo simulation. The phase diagram (temperature as a function of concentration c) shows ferromagnetic, antiferromagnetic and spin canted phases.
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Kazuo Gesi, Masashi Iizumi
1984 Volume 53 Issue 12 Pages
4271-4278
Published: December 15, 1984
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The normal-incommensurate phase transition in K
2ZnCl
4 was studied by neutron scattering measurements. A well-defined soft phonon behavior was not observed above the normal-incommensurate transition temperature of
Ti=288°C. Diffuse scattering develops around (
h, 0,
l±0.3) as temperature approaches
Ti from above, and the peak intensity obeys a Curie-Weiss law above
Ti. The results indicate that the normal-incommensurate phase transition in K
2ZnCl
4 can be interpreted as an order-disorder process.
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Kozo Hoshino
1984 Volume 53 Issue 12 Pages
4279-4283
Published: December 15, 1984
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Analytic expressions for the excess entropy in the hard-sphere system, the charged-hard-sphere (CHS) system and the classical one-component plasma (OCP) are summarised. The excess entropy of liquid alkali metals is discussed in relation to these model systems. It is shown that, to reproduce the observed excess entropy, a significantly reduced values of plasma parameter have to be used in the CHS system as well as in the OCP.
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Shin-ya Miyatani
1984 Volume 53 Issue 12 Pages
4284-4299
Published: December 15, 1984
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One-dimensional diffusion equation for chemical or ambipolar diffusion in ionic-electronic mixed conductors is solved under various experimental conditions. (1) Electronic or ionic electrodes are set at arbitrary positions of specimen having various end conditions: (A) Both ends of specimen are left free. (B) Large blocks of the material which is the same as that of the specimen are attached at both ends so that the concentration of ions at the ends is kept constant. (C) Small blocks of the specimen material are attached at both ends. (2) Atomic electrodes—combined electronic and ionic electrodes—are used. (3) Constant voltage is applied between two ionic electrodes attached at both ends of the specimen, instead of current intensity being kept constant. Experiments are carried out on silver chalcogenides, typical mixed conductors, showing good agreement with calculation results.
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Kazuyuki Matsumoto, Takeo Izuyama
1984 Volume 53 Issue 12 Pages
4300-4308
Published: December 15, 1984
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In a quantum lattice of closely packed hard core fermions such as hcp
3He, the tunneling motion for particle exchange is strongly coupled with zero-point lattice vibrations. The hybridization of the exchange tunneling and the zero-point vibration is considered by a simplified model. In this model the exchange of a nearest neighbour pair of fermions is supposed to grow rapidly when the third fermion closest to the pair is displaced to make enough space for the exchange tunneling.
Such displacement is assumed to be described by the Einstein model. The high temperature expansion series are obtained for the specific heat, for the pressure and for the susceptibility. It is shown that the susceptibility deviates from the Curie law in the direction usually seen in ferromagnets.
It is demonstrated, however, that the hcp quantum solid does not exhibit the simple ferromagnetic spin order in the low temperature phase.
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Shuzo Takano, Yoshimasa Kumashiro, Kazutaka Tsuji
1984 Volume 53 Issue 12 Pages
4309-4314
Published: December 15, 1984
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Electrical measurements of n- and p-Pb
1−xGe
xTe have been made between 4.2 K and 300 K. Below 40 K, resistivity exhibits anomalous behaviours similar to the Kondo effect in a dilute magnetic alloy. The anomaly is strongly correlated with the phase transition temperature. The formation of the pseudo-spins and the effect of their ordering on the resistivity anomaly are discussed.
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K\={o}ki Takanashi, Hiroshi Yasuoka, Kenji Kawaguchi, Nobuyoshi Hosoit ...
1984 Volume 53 Issue 12 Pages
4315-4321
Published: December 15, 1984
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A
51V NMR investigation has been made on the magnetic properties, particularly the interface magnetism, of an Fe–V metallic superlattice. Three kinds of signals have been observed; the two kinds associated with the atomic layers having induced V magnetic moments at the interface region, and the other with the nearly nonmagnetic sites in the more distant V layers. From the distribution of the hyperfine field it is concluded that the interface atomic layer is the mixture of Fe(50%)–V(50%) atomic concentration with a positive atomic short range order, and that the compositional modulation is restricted to three atomic layers at the interface. It is also found that the hyperfine field at the nearly nonmagnetic sites has an anisotropy which can not be expected in random alloys.
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Takeshi Fukami, Naoyuki Inoue, Shoichi Mase
1984 Volume 53 Issue 12 Pages
4322-4331
Published: December 15, 1984
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By means of measurements of the ultrasonic attenuation and velocity change, we have derived the magnitude of McMillan’s parameter λ of the oxide superconductor BaPb
1−xBi
xO
3 (
x=0.20–0.25). In this derivation we have assumed that the interaction between the conduction electrons and the sound waves is of the deformation potential type and the magnetic field dependent part of the attenuation at
T<
Tc is contributed from the normal conduction electrons. The value obtained is λ∼0.85 for the sample with
Tc=10.5 K. It is shown that a relatively large deformation potential constant |
Vd|=2.0 eV, which is 2.7 times larger than the Fermi energy and comes into λ in square, counterbalances the small density of states of this material and consequently leads to a reasonably large magnitude of λ for this rather semimetallic material.
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Hiizu Nakanishi
1984 Volume 53 Issue 12 Pages
4332-4343
Published: December 15, 1984
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Using an electron-phonon system, the problem of the competition between the superconductivity and the itinerant ferromagnetism is investigated. We calculate the free energy assuming the ferromagnetic and superconducting order and obtain the transition temperatures, the order parameters, and the specific heat. As a result, we show that only the successive transition, para normal→ferromagnetic→superconducting state on cooling, is possible for this system. This coincides with the transition which Y
9Co
7 shows.
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Fusayoshi J. Ohkawa, Hidetoshi Fukuyama
1984 Volume 53 Issue 12 Pages
4344-4352
Published: December 15, 1984
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Various types of anisotropic superconductivity have been investigated near its transition temperature in the periodic Anderson Hamiltonian with a weak attractive interaction between the nearest neighbor
f electrons. The superconductivity with the
s-,
p- or
dγ-symmetry is possible in a model where the
f sites form a simple cubic lattice. Due to the finite range of the interaction, even the
s-symmetry Cooper pairs can be anisotropic. This anisotropic
s-wave superconductivity has many different properties from the ordinary BCS superconductivity if the Fermi wave vector is large; the transition temperature
Tc can be significantly reduced by nonmagnetic impurities, the specific heat jump can be smaller than the BCS value, and the energy gap near
Tc can vanish along lines on the Fermi surface. The competition among different symmetries is discussed.
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Hiroshi Maeta, Fumihisa Ono, Tomoyoshi Kittaka
1984 Volume 53 Issue 12 Pages
4353-4358
Published: December 15, 1984
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Magnetic torque measurements have been made at 77 K for a single crystal disc of pure iron before and after a fast neutron irradiation at 5 K and after successive isochronal annealings at various temperatures between 77 K and 293 K. The observed torque curve after the irradiation contains both uniaxial and biaxial components. By analyzing the irradiation-induced torque and its change during isochronal annealings, the existence of 110-dumbbells has been confirmed, and the mechanism of the aggregation of interstitials and the change in their arrangements predicted theoretically by Bullough and Perrin have experimentally been proved.
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Kazuyoshi Ichinose, Katsuyuki Fujiwara, Hiroshi Yoshie, Hiroyuki Nagai ...
1984 Volume 53 Issue 12 Pages
4359-4361
Published: December 15, 1984
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Nuclear magnetic resonance of
27Al nuclei in (Gd
1−xTb
x)Al
2 has been observed at 4.2 K as a function of Tb concentration. Two peaks are observed and their positions decrease almost linearly with Tb concentration, indicating that the gadolinium moment direction does not change all over the concentration. The transferred hyperfine fields from rare earth ions in these compounds are analysed from RKKY theory.
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Shigeki Matsunaga, Shin’ichi Takeda, Shigeru Tamaki
1984 Volume 53 Issue 12 Pages
4362-4366
Published: December 15, 1984
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The magnetic susceptibilities of liquid Na–Pb alloys have been measured as a function of temperature and the electron susceptibilities of these alloys are extracted under the assumption of the partial formation of chemical short range order of Na
4Pb.
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Takashi Miyamoto, Yutaka Nakai, Nobuhiko Kunitomi
1984 Volume 53 Issue 12 Pages
4367-4372
Published: December 15, 1984
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Average magnetic moment of Mn in bcc Fe
90Mn
5Cr
5 alloy has been studied by means of polarized neutron diffuse scattering in order to investigate the anomalous magnetic behavior of Mu impurity in Fe. By assuming the average magnetic moment of Fe and Cr to have the same value as in an Fe
95Cr
5 alloy, we have determined the average magnetic moment of Mn at temperatures of 10 K, 150 K, 295 K and 383 K. The value of Mn average magnetic moments obtained for this alloy is larger than that in an Fe
95Mn
5 alloy at all temperatures. A simple nearest neighbor model has been discussed in which Mn atoms in Fe have either positive or negative moments according to the various environmental conditions. In Fe(Mu, Cr) alloys, the negative Mn moments will always flip to positive direction if it has at least one Cr atom in its nearest neighboring shell. This model has explained the experimental results at least qualitatively.
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Fumitaka Matsubara, Sakari Inawashiro
1984 Volume 53 Issue 12 Pages
4373-4385
Published: December 15, 1984
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A Monte Carlo study of a hexagonal Ising Antiferromagnet reveals the occurrence of a new type of modulated phase in which a spin structure described by using three sublattices is randomly modulated in the lattice. The order parameter of this phase is not individual sublattice magnetizations but a symmetric function of them which corresponds to the magnetic structure factor
F(1/3, 1/3, 0). As the temperature is decreased, this phase gradually changes into a usual homogeneous ferrimagnetic phase. This process is discussed in detail. It is suggested that this modulated phase occurs in CsCoCl
3 and CsCoBr
3.
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Satoru Inagaki, Hidetoshi Fukuyama
1984 Volume 53 Issue 12 Pages
4386-4394
Published: December 15, 1984
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The phase diagram of the stable states in the presence of the magnetic field is obtained for the quasi-one-dimensional Heisenberg antiferromagnet coupled with the lattice distortion. The spin-flop state and the state having spin-solitons appear as the possible ground states besides the spin-Peierls state and the Néel state which are the ground state in the absence of the magnetic field. Three types of field-induced phase transitions are shown to exist depending on the relative strength of the weak interchain exchange interaction to the spin-lattice coupling.
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Mitsutaka Fujita, Kazushige Machida
1984 Volume 53 Issue 12 Pages
4395-4404
Published: December 15, 1984
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Spin-Peierls transitions under magnetic fields in a Heisenberg antiferromagnetic linear chain coupled to the spin-lattice distortion are discussed theoretically. Based on the mean-field Pytte Hamiltonian thermodynamic quantities such as magnetization, susceptibility and specific heat are derived, using the soliton lattice solution for the incommensurate state which takes into account infinite numbers of higher harmonics. The experimental data on TTF–MBDT (M=Cu and Au) and MEM (TCNQ)
2 are examined.
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Kazuo Gesi, Kunio Ozawa
1984 Volume 53 Issue 12 Pages
4405-4412
Published: December 15, 1984
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Effect of hydrostatic pressure on the antiferroelectric phase transitions in NH
4H
2AsO
4 and deuterated analogue (deuterium concentration ∼80%) was studied by dielectric constant measurements at high pressures up to about 0.8 GPa. The transition temperature linearly decreases with increasing pressure with the ratios of −19.7 K GPa
−1 and −14.5 K GPa
−1 for NH
4H
2AsO
4 and the deuterated compound, respectively. The pressure effect is compared with previously reported results of other KH
2PO
4-type ferro- and antiferroelectric crystals.
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Kazuoki Kuramoto, Hiroshi Motegi, Eiji Nakamura
1984 Volume 53 Issue 12 Pages
4413-4419
Published: December 15, 1984
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Complex dielectric constants of KH
2PO
4 single crystals along the
a- and the
c-axes have been measured in the temperature range from 2.5 K to 30 K at frequencies between 10 Hz and 20 kHz. Dielectric dispersions with small loss peaks are observed in both directions. The dispersion along the
c-axis (dispersion C) is found only in the multidomain crystal, whereas the dispersion along the
a-axis (dispersion A) is insensitive to the domain structure. The relaxation frequency of the dispersion C obeys the Arrhenius’ relation with the extremely small activation energy of 0.019 eV. A large deviation from the Arrhenius’ relation is found for the dispersion A. The temperature dependence of the dispersion frequency and the profile of the dispersion curves of the dispersion A are well explained by a damped oscillator model with a Gaussian distribution of the resonant frequencies.
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Masayoshi Obashi, Tokuo Matsukawa
1984 Volume 53 Issue 12 Pages
4420-4424
Published: December 15, 1984
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X-ray
K absorption edge structures of chlorine ion in trans-[CoCl
2(en)
2]NO
3, trans-[CoCl
2(en)
2]Cl and [Co(en)
3]Cl
3·3H
2O are measured with a high-resolution vacuum two-crystal spectrometer. The spectra, except that of [Co(en)
3]Cl
3·3H
2O having no ligand Cl
− ion, show an extremely narrow absorption line at the absorption threshold. All of the spectra show a broad absorption band extending to the higher energy region of the narrow absorption line. It is found that a characteristic of the respective spectra depends on the different chemical states between the cobalt and chlorine ions. The result is interpreted on the basis of molecular orbital theory.
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Nobuhiko Yamashita, Shozo Iwasaki, Sumitada Asano, Masakazu Ohishi, Ke ...
1984 Volume 53 Issue 12 Pages
4425-4431
Published: December 15, 1984
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The details of the luminescence spectra and the decay characteristics of the luminescence have been examined over a wide range of temperature. At low temperatures, the luminescence decay curve after the
A-band excitation has two components, fast and slow. The difference between the decay times, about 10 ns and 4.1 ms at 4.2 K, enables one to decompose the emission spectrum into the
3T1u→
1A1g and
3A1u→
1A1g bands by time-resolved emission spectroscopy. The zero-phonon line at 445.3 nm of the former band and the zero-phonon line (
A0) at 460.7 nm and the one-phonon line at 465.0 nm of the latter band are observed at 6 K. The
A0 line grows under an external magnetic field. The optical excitation mechanism has been also examined by observing the excitation spectra at various temperatures.
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Takenari Goto, Yoshihiro Sasaki
1984 Volume 53 Issue 12 Pages
4432-4437
Published: December 15, 1984
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Absorption spectra in a very thin film of PbI
2 have been measured by using multiple total reflections at 90 K. A new band appearing at 21.14 kcm
−1 is assumed to be associated with an exciton located in a few layers adjacent to vacuum, and the exciton binding energy of 650±50 cm
−1 is larger than that of the bulk exciton. This larger binding energy suggests quasi-two dimensionality of this exciton.
Moreover, a step and a plateau appear at 20.8 kcm
−1 and in 22–23 kcm
−1, respectively. These structures are concluded to be due to the band-to-band transition in the quasi-two dimensional electronic structure.
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Hiroyasu Shimizu, Kazuyuki Matsumoto
1984 Volume 53 Issue 12 Pages
4438-4444
Published: December 15, 1984
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The Raman spectra of solid bromoform and bromoform-
d have been measured up to 100 kbar at 300 K in a gasketed diamond anvil cell. The pressure dependence of six intramolecular and three intermolecular vibrations has been investigated in comparison with the Raman results of a low-temperature solid at atmospheric pressure. The α→β and the β→γ phase transition at respective pressures 10 and 42 kbar are presented by the high-pressure behavior of the ν
3 intramolecular mode and the intermolecular vibrations. The mixing state of the β and the γ phase was found at pressures between 34 and 55 kbar. The γ phase metastable at atmospheric pressure becomes stable at high pressures above 42 kbar.
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Yoshinori Tokura, Takao Koda, Gunzi Saito, Tadaoki Mitani
1984 Volume 53 Issue 12 Pages
4445-4455
Published: December 15, 1984
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In order to investigate the effect of doping on the neutral-to-ionic phase transition, reflection spectra due to the intramolecular excitations have been measured on TTF-
p-chloranil single crystals doped with the substitutional weak acceptor, trichloro-
p-benzoquinone, at various temperatures and dopant concentrations. The thermal shifts of the spectra are considerably blurred by doping in contrast with a sharp spectral change at
Tc=84 K in pure crystal. It is concluded that the phase transition in doped crystals occurs inhomogeneously due to a binary phase separation into quasi-ionic and quasi-neutral regions even below
Tc. On the basis of these results, a microscopic model is presented for the effect of impurities on the neutral-to-ionic phase transition in TTF-chloranil crystal.
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Makoto Kuwata
1984 Volume 53 Issue 12 Pages
4456-4470
Published: December 15, 1984
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Highly sensitive momentum-space spectroscopy, named two-photon polarization spectroscopy (TPPS), is presented in the Z
3 exciton resonant region of CuCl. This spectroscopy is based on the induced optical anisotropy associated with the formation of
Γ1 excitonic molecules (EM’s). By this method the following facts are confirmed: the upper branch polaritons (UBP’s) and the lower branch polaritons (LBP’s) coexist in the wide energy range above the longitudinal exciton energy; the conversion of UBP into LBP occurs in the reflection at the sample boundary; the EM relaxation depends on the wave number in the large wave number region. From the quantitative analysis of the spectra, it has been found that the damping of the Z
3 exciton depends strongly on its energy in the L–T gap region. The prospects of the ABC problem are also discussed.
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