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Kohji Yamamoto
専門分野: Kinetic and transport theory of fluids; physical properties of gases.
1994 年 63 巻 9 号 p.
3193-3196
発行日: 1994/09/01
公開日: 1999/10/01
ジャーナル
認証あり
The effect of anisotropy in scattering on the electron transportproperties is examined in a model gas. The drift velocity as afunction of electric field has regions of a hump and of negativedifferential conductivity. The effect of forward- andbackward-dominant anisotropies in the inelastic scattering markedlyappears in the hump region, where the velocity distribution is highlyanisotropic. This is considered to be due to the combined effect ofthe anisotropies in scattering and in the velocity distribution.
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Tadao Honzawa, Yoshifumi Saitou
専門分野: The physics of plasmas and electric discharges.
1994 年 63 巻 9 号 p.
3197-3199
発行日: 1994/09/01
公開日: 1999/10/01
ジャーナル
認証あり
Breaking of slow ion-beam modes into wave packets in ion-beam-plasma systems is experimentally studied. When pump waves of the mode with a frequency around 200, kHz have amplitudes larger than a critical one, wave-breaking into many packets is observed to start at the axial position x~= 9, cm, and the packet amplitudes rapidly grow with increasing x.
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Hirohisa Endo, Takuya Tsuzuki, Makoto Yao, Yukinobu Kawakita, Kaoru Sh ...
専門分野: Structure of liquids and solids; crystallography.
1994 年 63 巻 9 号 p.
3200-3203
発行日: 1994/09/01
公開日: 1999/10/01
ジャーナル
認証あり
We have carried out quasielastic neutron scattering measurements on liquid tellurium (l-Te) at 460°C, and inelastic neutron scattering measurements on trigonal tellurium (t-Te) at 400°C, supercooled l-Te at 400°C and l-Te at 467°C. The quasielastic scattering peak is comparatively narrow at momentum transfer Q=2.0, Å
-1 where the first peak of the static structure factor is seen. The vibrational density of states (V-DOS) of supercooled l-Te has a three-band structure similar to that of t-Te, indicating that the chain structure is preserved in the liquid state. The V-DOS of l-Te changes remarkably with temperature, which strongly demonstrates the modification of chain structure in the liquid state.
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Shinya Iwai, Kazuhiro Fukushima
専門分野: Lattice dynamics and crystal statistics.
1994 年 63 巻 9 号 p.
3204-3206
発行日: 1994/09/01
公開日: 1999/10/01
ジャーナル
認証あり
We directly observe the wave propagation in a Fibonacci lattice as an electric signal by use of a transmission line, which is constructed under the rule of the Fibonacci sequence. The experimental result shows that the spatial structure of lattice oscillation has a self-similar nested structure. The structure factor for spatial variation of wave amplitude is also calculated.
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Touru Yamauchi, Katsuya Shimizu, Nao Takeshita, Mamoru Ishizuka, Kiich ...
専門分野: Electronic transport in condensed matter.
1994 年 63 巻 9 号 p.
3207-3209
発行日: 1994/09/01
公開日: 1999/10/01
ジャーナル
認証あり
The Hall coefficient of metallic iodine is measured in pressures up to 74, GPa at room temperature and in 30, GPa at 4.2, K. The carrier of the pressure-induced metallic iodine is found to be a hole in agreement with the theoretical prediction.
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Katsuhiro Nakamura, Ken Ito, Yositake Takane
専門分野: Electronic transport in condensed matter.
1994 年 63 巻 9 号 p.
3210-3213
発行日: 1994/09/01
公開日: 1999/10/01
ジャーナル
認証あり
Quantum and classical analyses are made on transport in an open Bunimovich stadium billiard in the perpendicular magnetic field B. The mild and violent undulations of quantum conductance g(B) in low- and high-field regions are due to the stability of the fully chaotic phase space in the underlying classical dynamics and to the transitional instability of the ergodic part which is rapidly replaced by the Kolmogorov-Arnold-Moser tori, respectively. This crossover is also signaled by a marked difference between gradients of cusp-shaped central peaks in the autocorrelation functions.
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Nobuo Furukawa
専門分野: Electronic transport in condensed matter.
1994 年 63 巻 9 号 p.
3214-3217
発行日: 1994/09/01
公開日: 1999/10/01
ジャーナル
認証あり
The Kondo lattice model with Hund's ferromagnetic spin coupling is investigated as a microscopic model of the perovskite-type 3d transitionmetal oxide La
1-xSr
xMnO
3. In the classical spin limit S=∞ and the infinite-dimensional limit D=∞, the one-body Green's function is exactly calculated. Transport properties of the system in the presence of magnetic fields are obtained. The giant magnetoresistance of this model, which is in good agreement with the experimental data of La
1-xSr
xMnO
3, is explained by the spin-disorder scattering process.
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Takashi Nishikawa, Yukio Yasui, Masatoshi Sato
専門分野: Electronic transport in condensed matter.
1994 年 63 巻 9 号 p.
3218-3221
発行日: 1994/09/01
公開日: 1999/10/01
ジャーナル
認証あり
The Mott-type metal-insulator transition has been successfully realized in a misfit-layer compound system La
1.17VS
3.17 by Sr substitution for La. The transport properties are found to exhibit anomalous behaviors which are very similar to those of high-T
c oxides, indicating that they are commonly found in systems having electrons with 2-dimensional nature located near the Mott metal-insulator phase boundary.
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Kenji Ishida, Yoshio Kitaoka, Kunisuke Asayama, Masaki Azuma, Zenji Hi ...
専門分野: Magnetics resonances and relaxations in condensed matter; MÖssbauer effect.
1994 年 63 巻 9 号 p.
3222-3225
発行日: 1994/09/01
公開日: 1999/10/01
ジャーナル
認証あり
Low-energy spin excitation in a spin S=1/2 two-leg ladder system SrCu
2O
3 has been investigated by Cu NMR. From an activated decrease of the nuclear-spin lattice relaxation rate, 1/T
1, in a T-range of 100--300, K, a spin gap, Δ, is demonstrated to open with a value of 680, K, which is in quantitative agreement with the theoretical value of Δ-- 0.5J=650, K, if the same value of 1300, K as in the square lattice system is used as the antiferromagnetic exchange coupling constant, J. It is furthermore deduced from the measurement of the spin-echo decay rate, 1/T
2G, that a magnetic coherence length, ξ/a (a: lattice spacing between Cu atoms along the chain), remains finite with (ξ/a)-- 13, comparable to a value in La
2CuO
4 near T
N. This class of cuprate is thus a frustrated quntum antiferromagnet (AF) with a spin gap.
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Takeshi Emoto, Ko Mibu, Nobuyoshi Hosoito, Teruya Shinjo
専門分野: Magnetics resonances and relaxations in condensed matter; MÖssbauer effect.
1994 年 63 巻 9 号 p.
3226-3229
発行日: 1994/09/01
公開日: 1999/10/01
ジャーナル
認証あり
In order to investigate the magnetic properties of nonmagnetic metal layers in multilayers, we prepared Co/Au multilayers in which
119Sn layers are inserted into Au layers, and applied Mössbauer spectroscopy. A fraction with large magnetic hyperfine fields was observed in the Mössbauer spectra, and thus magnetic polarization of conduction electrons in nonmagnetic layers is confirmed.
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Kenji Komatsu, Jun–ichi Wakita, Akio Nakahara, Mitsugu Matsushit ...
専門分野: Biophysics.
1994 年 63 巻 9 号 p.
3230-3233
発行日: 1994/09/01
公開日: 1999/10/01
ジャーナル
認証あり
Based on microscopic observations, a reproducible random-walker model is presented to simulate the growth of a bacterial colony. Random walkers expand their territory by pushing the wall surrounding their colony. Numerical studies revealed that the model can explain our experimental results obtained using the bacteria species Bacillus subtilis.
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Gen Yoneda
専門分野: Mathematical methods in physics.
1994 年 63 巻 9 号 p.
3235-3242
発行日: 1994/09/01
公開日: 1999/10/01
ジャーナル
認証あり
The previous paper I of this series presented four asymptotic conditions of smooth worldlines in Minkowski space and researched the inclusion relations between them. This paper moreover presents three asymptotic conditions that are used in special relativistic particle dynamics. (1) There is no end of the worldline. (2) From any point, the perpendicular to the worldline is drawable. (3) The acceleration vanishes asymptotically. The inclusion relations between seven conditions are researched by showing some inclusion relations and by examining some examples. Then the concluding Venn diagram is obtained.
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B. S. Sandhu, B. Singh, B. S. Ghumman
専門分野: Classical and quantum physics: mechanics and fields.
1994 年 63 巻 9 号 p.
3243-3248
発行日: 1994/09/01
公開日: 1999/10/01
ジャーナル
認証あり
The cross-section for two-photon Compton scattering for incident photons of energy 0.662, MeV and two emitted photons having energies greater than 50, keV has been measured at different scattering angles θ
1=30° to 150° and θ
2=π/2; φ
2=π. Our measured results, although of same magnitude, are consistently higher as compared to theory of Mandl and Skyrme. Some calculations of energy and direction of the recoil electron are also carried out to understand the important features of this weak process.
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Yoshihiro Nishiyama, Naomichi Hatano, Masuo Suzuki
専門分野: Statistical physics and thermodynamics.
1994 年 63 巻 9 号 p.
3249-3262
発行日: 1994/09/01
公開日: 1999/10/01
ジャーナル
認証あり
Numerical-diagonalization analyses of an effective Hamiltonian for the Haldane system are given; the phase diadram of this Hamiltonian was previously studied only by means of the Hatree-Fock approximation. Phase transitions of the transverse-Ising-model type are found, and the phase diagram in the λ-D plane is depicted. The dependence of the phase boundary on the next-nearest-neighbor competing interaction is also studied in this effective-Hamiltonian formalism. A physical point of view is obtained by inspecting the low-lying excitation spectra of the effective Hamiltonian, and the correspondence to the original Haldane system is discussed.
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Michihiro Shibata, Tomohiko Ikuta, Akihiro Taniguchi, Akihiko Osa, Aki ...
専門分野: Nuclear decay and radioactivity.
1994 年 63 巻 9 号 p.
3263-3272
発行日: 1994/09/01
公開日: 1999/10/01
ジャーナル
認証あり
The β-decay of
15159Pr
92 to the levels in
15160Nd
91 has been studied from the fission products of
235U using an on-line isotope separator (KUR-ISOL). Gamma-rays and conversion electrons have been measured. Conversion coefficients have been determined for the first time. The precise decay scheme is proposed up to 2430, keV. The newly observed 65 γ-rays and 16 levels are incorporated in it. The deduced level scheme of
151Nd was compared to the calculated level scheme on the basis of the rotation-vibration coupling model with a Nilsson potential. Low-lying levels were well reproduced by this model.
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N. M. Mettwalli, L. Kelany
専門分野: Nuclear reactions and scattering: specific reactions.
1994 年 63 巻 9 号 p.
3273-3279
発行日: 1994/09/01
公開日: 1999/10/01
ジャーナル
認証あり
From the projectile fragments, emerged from noncentral collisions of 60, AGeV/c
16O collisions in nuclear emulsion, He nuclei were singled out and followed for their interactions. Multiplicity characteristics of secondary charged particles from 434 inelastic He-emulsion interactions at 60, AGeV/c were compared with the corresponding ones from the same interactions at 2.1 and 4.5, AGeV/c. The multiplicity distribution of shower particles compared with Fermi model predictions, have shown that He-emulsion interaction at 60, AGeV/c can be considered as superposition of nucleon-nucleus and collective He-nucleus collisions. The multiplicity characteristics of grey and black particles are energy independent.
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Jae–Tack Jeong, Hyung–Jong Ko
専門分野: Fluid dynamics.
1994 年 63 巻 9 号 p.
3280-3287
発行日: 1994/09/01
公開日: 1999/10/01
ジャーナル
認証あり
Two-dimensional slow viscous stagnation flow around a vertical plate on a plane wall is investigated based on the Stokes approximation. An exact formal expression of the stream function is obtained by use of the Wiener-Hopf technique. From the formal expression obtained, the streamline patterns around the plate are shown and the force exerted on the plate is calculated. The flows near the corner and the leading edge of the plate are also discussed. By examining more general stagnation flows toward the plane wall, the procedure how a viscous corner eddy merges into the main flow is explained.
抄録全体を表示
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Hyung–Jong Ko, Jae–Tack Jeong
専門分野: Fluid dynamics.
1994 年 63 巻 9 号 p.
3288-3294
発行日: 1994/09/01
公開日: 1999/10/01
ジャーナル
認証あり
Two-dimensional slow stagnation flow towards a plate with a slit is investigated on the basis of the Stokes approximation. The flow fileds are obtained in a closed form by finding two analytic functions which are determined by solving a pair of Riemann-Hilbert problems. The discharge through the slit and the stress distributions on the plate are calculated. The features of the flow including the local behavior near a sharp edge as well as the formation of viscous eddies and saddle stagnation points are also determined. The streamline patterns for some typical cases are presented.
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James W. Bradley, Hiroshi Amemiya
専門分野: The physics of plasmas and electric discharges.
1994 年 63 巻 9 号 p.
3295-3302
発行日: 1994/09/01
公開日: 1999/10/01
ジャーナル
認証あり
The pre-sheath potential and ion flux to the sheath have beensolved in the case of beam-plasma interaction. A finite temperature isassumed for the beam. The break-down in the space-charge sheathformation and the uncertainty of the floating potential appearing onthe assumption of monoenergetic beams are avoided. The mono-energeticcase is treated consistently as a limit of the present theory. Thepotential of the pre-sheath boundary increases with the beam densityratio and shows an abrupt jump to a higher value above a criticalratio. The floating potential increases from the usual value as thebeam density ratio increases and tends to a value above the potentialequivalent of the beam energy. The abrupt jump of the pre-sheath, however, causes only a small discontinuity in the floatingpotential. The results are also relevant to Langmuir probestudies in beam-plasma systems.
抄録全体を表示
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Masayuki Yoshikawa, Masaru Masuzaki, Ritoku Ando
専門分野: The physics of plasmas and electric discharges.
1994 年 63 巻 9 号 p.
3303-3310
発行日: 1994/09/01
公開日: 1999/10/01
ジャーナル
認証あり
High frequency strong electric fields originating from interaction ofan intense short-pulse relativistic electron beam with an unmagnetizedplasma were measured using two optical diagnostic techniques; theStark shift measurement and the plasma satellite method. Strongelectric fields with Gaussian distribution existed in the plasma. Thedimensionless electrostatic energy density W-- 1.1. So the plasmawas in a strong Langmuir turbulent state. The strong field regionswere found to occupy a few percent of the beam volume. The final scaleof caviton was determined to be about 22 λ
D. The turbulentstate lasted about thirty times as long as the IREB duration. Thephoton intensity decreased exponentially, while the distribution ofelectric fields remained the same. These aspects are remain to beexplored further.
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Weixing Ding, Rikizo Hatakeyama, Seiji Ishiguro, Noriyoshi Sato
専門分野: The physics of plasmas and electric discharges.
1994 年 63 巻 9 号 p.
3311-3318
発行日: 1994/09/01
公開日: 1999/10/01
ジャーナル
認証あり
Measurements are performed on plasma responses to electron injectionsfrom a floated emissive endplate into a magnetized collisionlessplasma column produced in a single-ended Q machine. When low-energyand high-density electrons are injected, the plate can be charged uppositively, forming a stable potential barrier to prevent ions fromflowing toward the plate. There appears a drastic increase in theplasma density. In case of high-energy and low-density electronsinjected, however, a large electron sheath formed in front of theplate is always accompanied by a periodic change of plasma structure.
抄録全体を表示
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Keiichi Aoyama, Rikizo Hatakeyama, Weixing Ding, Noriyoshi Sato
専門分野: The physics of plasmas and electric discharges.
1994 年 63 巻 9 号 p.
3319-3325
発行日: 1994/09/01
公開日: 1999/10/01
ジャーナル
認証あり
Measurements have been performed on ion cyclotron oscillations inducedby a small emissive disc plate floating in a magnetized collisionlessplasma column. The oscillations are observed when the emission is solarge that the disc potential is higher than the plasmapotential. This means that the oscillations are generated even in theabsence of dc electric current passing through the plasma column ifthe disc potential is positive with respect to the plasmapotential. The situation is in contrast with the case of applyingpositive potentials to a small cold disc plate to generate the ioncyclotron oscillations, where a dc electric current is induced alongthe plasma column. Main features of the oscillations are consistentwith the “potential-driven” model for the generation of ioncyclotron oscillations.
抄録全体を表示
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Hitoshi Yamamoto, Takaaki Suisyu, Shinichi Yano, Masami Tanaka
専門分野: Structure of liquids and solids; crystallography.
1994 年 63 巻 9 号 p.
3326-3332
発行日: 1994/09/01
公開日: 1999/10/01
ジャーナル
認証あり
The cholesteric pitch (P) and its temperature dependence(ΔP/ΔT) were studied for the chiral nematicsinduced by the compounds having 1-methyl-heptyloxy phenyl group. Theortho-substitution of methyl or halogen atoms to the1-methyl-heptyloxy phenyl group decreased P and increasedΔP/ΔT. An energy barriers for intra-chainrotation around chiral center of 1-methyl-heptyloxy phenyl group and astrength of nematic inter-molecular interaction were evaluated usingan empirical molecular orbital calculating method. As the result, itwas proposed that the conformational structure of 1-methyl-heptyloxyphenyl group predominantly controls P and ΔP/ΔTfor the present systems.
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Takao Furubayashi, Takehiko Matsumoto, Takatsugu Hagino, Shoichi Nagat ...
専門分野: Structure of liquids and solids; crystallography.
1994 年 63 巻 9 号 p.
3333-3339
発行日: 1994/09/01
公開日: 1999/10/01
ジャーナル
認証あり
Crystal structure and magnetic susceptibility were investigatedfor a thiospinel compound CuIr
2S
4, which exhibits a transitionfrom metallic to insulating on cooling at the transition temperatureT
c of 230, K. It was found that the transition is accompanied by afirst-order structural transition. As the compound is cooled throughT
c, the structure transforms from cubic to tetragonal with a volumecontraction of 0.7%. The tetragonal phase has an axial ratio of about 1.03. Magnetic susceptibility, which is paramagnetic in the metallicregion, decreases sharply and becomes diamagnetic at T
c on cooling. The susceptibility is mostly temperature independent in each regionabove and below T
c. Magnetic measurements also revealed that highpressure stabilizes the insulating phase, in contrast with most of thecompounds that exhibit metal-insulator transitions. Possiblemechanisms of the metal-insulator transition are discussed.
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Katsuhiko Hasebe, Takanao Asahi, Hironobu Kasano, Hiroyuki Mashiyama, ...
専門分野: Equations of state, phase equilibria, and phase transitions.
1994 年 63 巻 9 号 p.
3340-3343
発行日: 1994/09/01
公開日: 1999/10/01
ジャーナル
認証あり
X-ray scattering of K
2ZnCl
4 was studied near thetransition temperature at 145, K, by the use of a source ofsynchrotron radiation and ordinary X-ray source. Characteristicdiffuse scattering was observed above the transition temperature nearsuperlattice reflections which appears below 145, K. An incommensuratephase was not found just above 145, K.
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K. S. Sidhu, S. S. Sekhon, S. S. Chandra
専門分野: Transport properties of condensed matter (nonelectronic).
1994 年 63 巻 9 号 p.
3344-3348
発行日: 1994/09/01
公開日: 1999/10/01
ジャーナル
認証あり
Copper glasses (CuI+Cu
2O+MoO
3) have been prepared byin-situ quenching of mixtures molten (i) in air (ii) under N
2 beingcontinuously flushed, (iii) in static vacuum with initial pressure of10
-6, Torr and (iv) in vacuum being continuously pumped. Thesamples prepared under different conditions had differentionic/electronic transference number. The electronic part ofconductivity has been explained in terms of Mo
6+ → Mo
5+and Cu
+ ⇔ Cu
++ conversion. The presence ofCu
++ and Mo
5+ has been established by ESR studies.
抄録全体を表示
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Yoshikazu Tanaka, Yoshiharu Sakurai, Susumu Nanao, Nobuhiro Shiotani, ...
専門分野: Electron states in condensed matter.
1994 年 63 巻 9 号 p.
3349-3355
発行日: 1994/09/01
公開日: 1999/10/01
ジャーナル
認証あり
A single Al
59.3Li
29.3Cu
11.4 icosahedral quasicrystalis prepared with the Bridgman method. To study the electronicstructure of this phase, high resolution Compton profiles along theaxes of the five- and two-fold symmetries of the single quasicrystalphase have been measured with 60-keV synchrotron radiation X-rays. TheFermi cutoffs are observed clearly in the profiles. Anisotropy in theelectron momentum distribution is not found. Although the valenceelectron profiles can be fitted with an inverted parabola, thefree-electron model does not explain the shape of profiles and themomentum values of the Fermi cutoffs. Based on a concept of thequasi-Brillouin zone boundary the effects of strong electron-latticeinteraction on the electron momentum distribution have been examined.
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M. Pal, P. Brahma, D. Chakravorty
専門分野: Electronic transport in condensed matter.
1994 年 63 巻 9 号 p.
3356-3360
発行日: 1994/09/01
公開日: 1999/10/01
ジャーナル
認証あり
Bismuth substituted barium hexaferrites in the composition series BaO·(6-x)Fe
2O
3· xBi
2O
3 with 0
s with s having values in the range 0.5 to 0.8. The electrical conductivity is believed to arise due to the creation of Fe2+ sites by the reducing action of Bi3+ ions. The ac conductivity variation is explained on the basis of overlapping-large-polaron-tunnelling (OLPT) mechanism.
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Yositake Takane, Hiroshi Otani
専門分野: Electronic transport in condensed matter.
1994 年 63 巻 9 号 p.
3361-3368
発行日: 1994/09/01
公開日: 1999/10/01
ジャーナル
認証あり
A simple method is outlined for the calculation of theweak-localization correction to resistance for metallic wire systemsin contact with a superconductor. To illustrate the approach, calculations of the resistance correction are carried out for simplesystems. We found that the weak-localization correction for anormal-metal wire is enhanced when an end of the wire is connected toa superconductor instead of a normal-metal probe. A similarenhancement is also seen in a normal-metal ring in contact with asuperconductor. Resistance oscillations with unusual period hc/4eare discussed for a doubly-connected structure containing asuperconducting segment.
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Masahiko Hayashi, Hidetoshi Fukuyama
専門分野: Superconductivity.
1994 年 63 巻 9 号 p.
3369-3391
発行日: 1994/09/01
公開日: 1999/10/01
ジャーナル
認証あり
The electromagnetic linear response both in the lattice stateand liquid state of vortices in type-II superconductors are studiedbased on the dynamical superfluid density. The calculations arecarried out paying special attention to the difference of the internaland the external vector potential. By use of the obtained dynamicalsuperfluid density the static superfluid density, the electricconductivity and the magnetic permeability are studied. A significantdifference in responses between the two states is found especially inthe Lorentz force free configuration, namely when the supercurrentflows in the direction parallel to the applied magnetic field; thevortex lattice state is superconducting in this direction while theliquid state is not becaue of the vortex entanglement and cuttingeffects. The magnetic susceptibility, especially in lattice state, hasbeen examined in detail.
抄録全体を表示
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Tomohei Sasada
専門分野: Superconductivity.
1994 年 63 巻 9 号 p.
3392-3398
発行日: 1994/09/01
公開日: 1999/10/01
ジャーナル
認証あり
Recent observations of a stretched exponential relaxation ofthe current on a ceramic Y-Ba-Cu-O by Masuda et al. and of thetorque on a ceramic La-Ba-Cu-O by Giovannella et al. are suggestiveof the existence of a hierarchically organized vortex glass. We obtainthe I-V / characteristics for such a vortex glass to show that it is asuperconducting state with zero resistance below the glass-transitiontemperature. The formation of pinning centers and its relevance tophase transitions are discussed briefly.
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Akihiko Sumiyama, Masahito Nakagawa, Yasukage Oda
専門分野: Superconductivity.
1994 年 63 巻 9 号 p.
3399-3404
発行日: 1994/09/01
公開日: 1999/10/01
ジャーナル
認証あり
The maximum supercurrent I
c passing through the S(Nb)-N(Cu doped with Mn)-S(Nb) junction made of Cu-clad Nb wire has been measured down to 30, mK, in order to investigate the relation between the superconducting proximity effect and the Kondo effect. The maximum supercurrent becomes small with an increase in Mn concentration and remarkably with a decrease in electronic mean free path in Cu. The electronic mean free path dependence of I
c may be explained qualitatively in consideration of the spin flip scattering and the RKKY interaction of Mn impurities. The Meissner effect induced by the proximity effect in Cu-clad Nb wire can be understood through the behavior of the coherence length ξ
N in Cu which is derived from I
c.
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Masaharu Kawachi, Makoto Hagiwara, Kuniyuki Koyama, Motohiro Matsuura
専門分野: Superconductivity.
1994 年 63 巻 9 号 p.
3405-3411
発行日: 1994/09/01
公開日: 1999/10/01
ジャーナル
認証あり
The superconductive ordering of a YBa
2Cu
4O
8 ceramic with a single phase and of homogeneous sub-micron size grains, is studied by systematic DC magnetic measurements under weak magnetic fields. Successive phase transitions of a hierarchical nature are identified to occur at two temperatures T
C1(~= 80, K) and T
C2(~= 37, K). The transition at T
C1 is that from the normal into the intra-grain superconductive state. The transition at T
C2 is that into the inter-grain superconductive state and results in an infinite superconductive network over the whole sample. Taking a possible Josephson junction type coupling into account, the second transition at T
C2 is speculated to be a long range ordering among the superconductive grains and similar to that for a three-dimensional XY ferromagnet.
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Hidekazu Tanaka, Kazuhisa Kakurai
専門分野: Magnetic properties and materials.
1994 年 63 巻 9 号 p.
3412-3420
発行日: 1994/09/01
公開日: 1999/10/01
ジャーナル
認証あり
Structural and magnetic phase transitions in RbVBr
3 have been investigated by neutron scattering. A structural phase transition occurs at T
t=89.6, K. The unit cell below T
t is described by enlarging that of CsNiCl
3 to √{3}a, √{3}a, c. The intensity of the nuclear Bragg peak forQ=(1/3, 1/3, 2) varies continuously at T
t, implying that the transition is of the second kind or very close to it. RbVBr
3 undergoes two magnetic phase transitions at T
N1=28.1, K and T
N2=21.0, K due to the inequality of the interchain exchange couplings which arises from the structural phase transition. The critical exponent of the sublattice magnetizations for T
N1 is found to be β
1=0.32± 0.01 which is a little smaller than the exponent of the three dimensional XY universality. The intensity of the magnetic (1, 1, 1) reflection which is very weak in the intermediate phase grows steeply below T
N2. This indicates that the partially disordered collinear structure is acquired in the intermediate phase.
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Masaaki Kontani, Takashi Nishioka, Yoshitaka Hamaguchi, Hisayuki Matsu ...
専門分野: Magnetic properties and materials.
1994 年 63 巻 9 号 p.
3421-3430
発行日: 1994/09/01
公開日: 1999/10/01
ジャーナル
認証あり
We report systematical measurements of specific heat, electrical resistivity and magnetization on heavy-fermion antiferromagnets U
14Au
51-xCu
x (0≤ x≤ 9) and UAu
3 and a paramagnet UAu
2 in wide temperature and magnetic field ranges. The linear-like decrease of T
N of U
14Au
51-xCu
x with x, corresponding to the decrease of the lattice constants, is interpreted as a chemical pressure effect. The high field magnetization process of U
14Au
51-xCu
x at 4.2, K exhibits a metamagnetic-like jump around 25, 23 and 14, T for x=0, 3 and 9, respectively. The heavy fermion ground states of U
14Au
51 and UAu
3 have been studied by specific heat measurements down to 0.5, K in magnetic fields upto 8, T.
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Kousuke Yakubo, Takamichi Terao, Tsuneyoshi Nakayama
専門分野: Magnetic properties and materials.
1994 年 63 巻 9 号 p.
3431-3441
発行日: 1994/09/01
公開日: 1999/10/01
ジャーナル
認証あり
The fracton dynamics of percolating Heisenberg antiferromagnets are studied in terms of a dynamic scaling argument and large-scale numerical analysis. It is shown that the spectral (or fracton) dimension for antiferromagnetic fractons, ˜{d}
AF, is bounded by the relation ˜{d}
AF≤ 1. The densities of states (DOS) are calculated for very large percolating antiferromagnets at the critical concentration p
c formed on d=2, 3, and 4 simple cubic lattices. It is concluded, from the calculated DOS's, that the spectral dimensions ˜{d}
AF are very close to unity for any Euclidean dimension d(≥ 2). We have also calculated the DOS for percolating antiferromagnets above p
c in order to clarify the crossover behavior from extended magnons to fractons. In addition, the dynamical structure factor S(q, ω) is investigated both analytically and numerically. It is found, postulating a single-length scaling, that the asymptotic behaviors can be characterized by two exponents, the dynamical exponent z
AF and a new exponent y. The numerical results for S(q, ω) support the validity of the single-length-scale postulate.
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Rikio Konno
専門分野: Magnetic properties and materials.
1994 年 63 巻 9 号 p.
3442-3446
発行日: 1994/09/01
公開日: 1999/10/01
ジャーナル
認証あり
We report the magnetization process with the SU(4) Kondo model (the single site Coqblin-Schrieffer model) taking into account the four 5f-levels from the lowest level split by the hexagonal crystalline field of the total spin J=4. We treat the model with the exact solution at the ground state. As an example, we investigate how far the theoretical result is fitted into the experimental results in UPd
2Al
3 within this approach. The crystalline field parameters used are inferred from those determined by the experimental data.
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Yutaka Nakai
専門分野: Magnetic properties and materials.
1994 年 63 巻 9 号 p.
3447-3453
発行日: 1994/09/01
公開日: 1999/10/01
ジャーナル
認証あり
Distributions of hyperfine magnetic field for four α-Mn specimens with 0.1 to 0.2, at.\spectra. The distributions at very low temperature have a sharp peak and a steep decline in the field magnitude, contrasting with the broad distribution of β-Mn(Sn) alloy which has a characteristic gradual decline in the field magnitude. The hyperfine field distribution for the 0.2, at.\ emperature-range below the Néel temperature. The Néel temperature obtained from the Mössbauer study rapidly increases up to 180, K by adding 0.2, at.\determined by neutron diffraction.
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Tomonobu Ohyama, Hiroyuki Shiba
専門分野: Magnetic properties and materials.
1994 年 63 巻 9 号 p.
3454-3473
発行日: 1994/09/01
公開日: 1999/10/01
ジャーナル
認証あり
Neutron scattering experiments have revealed that the excitation spectrum in quasi-one-dimensional ABX
3-type antiferromagnets, such as CsNiCl
3, differs appreciably from the prediction of the conventional linear-spin-wave theory even in the ordered phase. It was shown in a previous paper that the spectrum could be explained well by including two-magnon excitation processes in the spin-wave expansion. Here the theory is extended to study magnetic properties of CsNiCl
3 in a magnetic field. The magnetization curve is found to vary with the field nonlinearly with about a half of the classical value. The excitation spectrum is remarkably affected by nonlinear processes. In addition to the effects which are seen at zero field, a hybridization effect and two-magnon peaks in a certain polarization are found to be significant. The results are compared with available experiments and phenomenological theories previously proposed.
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Shigeyoshi Mori, Isao Mannari, Isao Harada
専門分野: Magnetic properties and materials.
1994 年 63 巻 9 号 p.
3474-3480
発行日: 1994/09/01
公開日: 1999/10/01
ジャーナル
認証あり
We study effects of a transverse magnetic field on theproperties of the one-dimensional spin-1/2 Ising-like antiferromagnet. In order to emphasize the relevant role of domain walls betweenopposite antiferromagnetic domains, the spin Hamiltonian is exactlymapped to the interacting fermion Hamiltonian, via the dualtransformation as well as the Jordan-Wigner transformation. Within thegeneralized Hartree-Fock approximation, we find that the excitationspectrum exhibits characteristic features, which are explained as aresult of the different roles of the transverse field and of thetransverse components of the exchange interactions in the propagationof the domain wall. At a critical field where the excitation gapvanishes, a ground-state phase transition is found to take place inthe same manner as that in the transverse Ising model. In addition, wediscuss the relevance of our magnetization curve with regard toexperimental data in CsCoCl
3.
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Shinsaku Kambe, Takato Machi, Izumi Tomeno, Hiroshi Yasuoka, Akihiko H ...
専門分野: Magnetics resonances and relaxations in condensed matter; MÖssbauer effect.
1994 年 63 巻 9 号 p.
3481-3487
発行日: 1994/09/01
公開日: 1999/10/01
ジャーナル
認証あり
We have extracted the T-dependence of the dynamical susceptibility at q-- 0 and q-- Q from the spin-lattice and the spin-spin relaxation measurements at the Cu and O sites in the normal state of YBa
2Cu
4O
8. The estimated dynamical susceptibility suggests that the relation of T
1TK
spin=const does not hold around q=0. We have measured the temperature (T)-dependence of the Knight shift and the spin-lattice relaxation time at the Y site in the same sample. Based on the comparison between the observed T-dependence of T
1 at the Y site and the calculated one using the extracted single layer dynamical susceptibility, we have suggested the development of thesinglet or antiferromagnetic bi-layer coupling in the YBa
2Cu
4O
8.
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Tatsuo Kanashiro, Toshihiro Yamanishi, Yutaka Kishimoto, Takashi Ohno, ...
専門分野: Magnetics resonances and relaxations in condensed matter; MÖssbauer effect.
1994 年 63 巻 9 号 p.
3488-3493
発行日: 1994/09/01
公開日: 1999/10/01
ジャーナル
認証あり
The temperature dependence of the spin-lattice relaxation time for
7Li has been measured in a single crystal of LiNaSO
4 over the temperature range of 450, K--770, K. The result can be explained by a mechanism of vacancy diffusion. The activation energies for the hopping of Li
+ and Na
+ vacancies are estimated to be E
1=0.70, eV and E
2=1.20, eV, respectively. In addition, the ionic conductivity has been measured as a function of frequency from 500, Hz to 20, MHz and the value of 1.59, eV is deduced as the activation energy, E
m for the ionic diffusion in the extrinsic region. These values of E
1, E
2, E
m are well compared with the corresponding values of 0.70, eV, 1.24, eV and the intermediate value between 1.74, eV for Li
+ and 1.90, eV for Na
+ ions evaluated from the previous NMR measurements.
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Takayuki Goto, Shinji Kazama, Kazuya Miyagawa, Tetsuo Fukase
専門分野: Magnetics resonances and relaxations in condensed matter; MÖssbauer effect.
1994 年 63 巻 9 号 p.
3494-3503
発行日: 1994/09/01
公開日: 1999/10/01
ジャーナル
認証あり
La-based high-T
C oxides La
2-xBa
xCuO
4 (LBCO) and La
2-xSr
xCuO
4 (LSCO) show a local minimum in the curve of T
C versus x around 0.125 for LBCO and around 0.115 for LSCO. In order to investigate the origin of this local minimum, temperature dependence of
63/65Cu/
139La-NMR/NQR spectra has been studied on spray-dry-made samples with various Ba/Sr-concentrations. Existence of the antiferromagnetic ordering was confirmed by a significant broadening in the resonance lines at low temperatures below 35, K for LBCO (x≅ 0.125) and 32, K for LSCO (x≅ 0.115). By the analysis on the anisotropy in the broadening, the direction of the ordered field was found to be within the CuO plane. The hyperfine field and the Néel temperature showed a maximum at the Ba/Sr-concentration around which T
C is most suppressed, suggesting the crucial interplay between the antiferromagnetic ordering and the suppression in T
C.
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Seitaro Mitsudo, Hitoshi Yamazaki
専門分野: Magnetics resonances and relaxations in condensed matter; MÖssbauer effect.
1994 年 63 巻 9 号 p.
3504-3508
発行日: 1994/09/01
公開日: 1999/10/01
ジャーナル
認証あり
Parallel pumping experiments in yttrium iron garnet have been performed at a pumping frequency 9.45, GHz and at a temperature 4.2, K. Above the spin-wave instability threshold, auto-oscillations of magnon amplitude are observed. Just above the onset of the auto-oscillations, signal has character of intermittent. From time-series data, Poincaré return maps and distribution of laminar period lengths are obtained. These results are in agreement with the theory based on symmetrical mapping that describes the dynamics of Lorentz type flows. Bifurcation parameters obtained by the best fit with the theoretical relation are presented as a function of the microwave power. Relationship between the average of the laminar lengths and the bifurcation parameter is in good agreement with the theoretical prediction.
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Cheol Eui Lee, I. Choi, J. E. Kim, C. H. Lee
専門分野: Magnetics resonances and relaxations in condensed matter; MÖssbauer effect.
1994 年 63 巻 9 号 p.
3509-3514
発行日: 1994/09/01
公開日: 1999/10/01
ジャーナル
認証あり
We have studied the dynamics of paramagnetic CuF
2·2H
2O using a wide range of
1H and
19F NMR frequencies at room temperature. The temperature dependence of the spin-lattice relaxation was measured as well. Being a system of dense paramagnetic Cu
++ ions, CuF
2·2H
2O shows some features that can be expected from dilute paramagnetic systems, as well as some results that drastically deviate from the dilute paramagnetic approximations. Besides,
1H and
19F nuclei exhibit distinct external magnetic field dependences of the linewidth and the spin-lattice relaxation.
抄録全体を表示
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Naoshi Kato, Isao Yamada
専門分野: Magnetics resonances and relaxations in condensed matter; MÖssbauer effect.
1994 年 63 巻 9 号 p.
3515-3521
発行日: 1994/09/01
公開日: 1999/10/01
ジャーナル
認証あり
We report the results of antiferromagnetic resonance (AFMR) experiments carried out on KCuF
3 at various temperatures below T
N=39, K using both X- and K-band spectrometers being respectively operated at 9.1 and 23.4, GHz. By measuring and analyzing temperature and frequency dependence of the in-plane angular change of the AFMR field, this study reconfirms the presence of a strong interdependent effect of the effective anisotropy fields H
DM and Δg· H, where H
DM arises from the Dzyaloshinsky-Moriya (DM) antisymmetric exchange interaction, tΔg is a difference between the two inequivalent g-tensors, and H is an external field. The frequency-field diagram calculated for the lowest-frequency mode which accounts for the frequencies referred to above shows spin-flopping which takes place from [1 1 0]
p to the direction perpendicular to [1 1 0]
p in the c-plane, where [ ]
p represents an axis in the unit cell of a perovskite structure.
抄録全体を表示
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Yutaka Itoh
専門分野: Magnetics resonances and relaxations in condensed matter; MÖssbauer effect.
1994 年 63 巻 9 号 p.
3522-3527
発行日: 1994/09/01
公開日: 1999/10/01
ジャーナル
認証あり
The temperature (T) dependence of the static staggered spin susceptibility χ(Q) for the high T
c Cu oxides, YBa
2Cu
3O
6.98 and YBa
2Cu
4O
8, extracted from the Cu nuclear spin-spin relaxation measurements is discussed. The self-consistent-renormalization (SCR) calculation for a two dimensional antiferromagnetic Fermi liquid well reporoduces the experimental Curie-Weiss-type T-dependence of χ(Q), but the random-phase-approximation does not. This shows that the Curie-Weiss-type χ(Q) of the high T
c Cu oxides results from the SCR spin fluctuations at finite temperatures but not from the strong nesting of the Fermi surface.
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Yoshihiro Ishibashi
専門分野: Dielectric properties and materials.
1994 年 63 巻 9 号 p.
3528-3532
発行日: 1994/09/01
公開日: 1999/10/01
ジャーナル
認証あり
The transition from the Ih phase (P6
3/mmc) to the XI phase, supposed to belong to the space group Cmc2
1, is discussed, respecting the symmetry aspect and the Bernal-Fowler rule. The transition derived from the present model is strongly of the first order in a good agreement with experimental observations, confirming the results obtained by previous works.
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Ryogo Hirota, Satoshi Tsujimoto
専門分野: Mathematical methods in physics.
1994 年 63 巻 9 号 p.
3533
発行日: 1994/09/01
公開日: 1999/10/01
ジャーナル
認証あり
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Kimiaki Konno, Hitoshi Oono
専門分野: Mathematical methods in physics.
1994 年 63 巻 9 号 p.
3534
発行日: 1994/09/01
公開日: 1999/10/01
ジャーナル
認証あり
