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Takashi Yamamoto
Subject area: Mathematical methods in physics.
1994 Volume 63 Issue 4 Pages
1223-1227
Published: April 01, 1994
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We explicitly construct the excited-state and derive the spectrum of the quantum Calogero-Sutherland-Moser model associated with the Weyl group B
N . We also discuss the asymptotic Bethe-ansatz method for this model.
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Takashi Nagatani
Subject area: Statistical physics and thermodynamics.
1994 Volume 63 Issue 4 Pages
1228-1231
Published: April 01, 1994
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A stochastic cellular automaton (CA) model is presented to study traffic flow in cities. In order to avoid traffic jam, cars are allowed to turn with probability p
turn when cars are blocked ahead by other cars. It is found that the jam-avoiding turn has an important effect on traffic jam. With increasing car density, jamming transitions occur from a maximal velocity phase, through a homogeneously moving phase, to a jamming phase, with a critical point. Above the critical point, the jamming transition does not appear. It is shown that allowing cars to turn results in a complex phase diagram.
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Ken–ichi Hattori, Kiyoshi Hayase, Yasuyuki Sato
Subject area: The physics of plasmas and electric discharges.
1994 Volume 63 Issue 4 Pages
1232-1236
Published: April 01, 1994
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A reversed-field pinch configuration with a four-separatrix toroidal divertor has been shown to be sustained without deterioration of MHD instabilities. By applying toroidal divertor fields, the plasma current increases by about 30
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Kiyoshi Sakaue, Naoki Toyoda, Hirofumi Kasatani, Hikaru Terauchi, Take ...
Subject area: Structure of liquids and solids; crystallography.
1994 Volume 63 Issue 4 Pages
1237-1240
Published: April 01, 1994
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We observed the relaxation behavior of the X-ray diffraction intensity arising from the glassy phase transition in C
60 single crystals for the first time. The (7 10 0) reflection which appeared below about 160, K showed an anomalous cusp-type feature near 90, K. It was found that this behavior strongly depended on the cooling rate of the specimen. Intensity relaxation of the reflection at 80, K at a cooling rate of 66, mK/s followed the single exponential law, I(t)∝ I
0(1-exp, (-t/τ )) with a relaxation time constant τ of 1.8× 10
4 seconds. These results strongly support those previously reported.
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Masaki Takesada, Toshirou Yagi
Subject area: Equations of state, phase equilibria, and phase transitions.
1994 Volume 63 Issue 4 Pages
1241-1244
Published: April 01, 1994
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The Brillouin scattering spectra of K
2ZnBr
4 have been observed near the first-order α-β transition point as a function of temperature.After the transition, the spectra of high-temperature β phase take different values of the frequency shift in each experimental run in contrast to the good reproducibility in low-temperature α phase.A large thermal hysteresis due to the first-order transition was observed in the temperature dependence of the Brilliouin frequency shift.The result seems to be explained well by the virtual intermediate states model recently proposed for the α-β transition mechanism.
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Akira Onuki
Subject area: Quantum fuids and solids: liquid and solid helium.
1994 Volume 63 Issue 4 Pages
1245-1249
Published: April 01, 1994
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We study the kinetics of nucleating droplets in metastable helium at ultralow temperatures. Our theory takes into account intense acoustic or electric field. The quantum nucleation rate can be greatly enhanced by the field when its frequency ω is higher than the inverse of tunnelling time τ
s. In particular, we present a new formula for the quantum nucleation rate in the limit ω τ
s>> 1.
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Kazuhiro Sano, Yoshiaki Ono
Subject area: Electron states in condensed matter.
1994 Volume 63 Issue 4 Pages
1250-1253
Published: April 01, 1994
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We investigated the one-dimensional extended Hubbard model with the on-site interaction U and the nearest-neighbor interaction V by using the numerical diagonalization method. Assuming the Luttinger liquid relations, we obtained the phase diagram of the ground state on the U-V plane. In the weak coupling region, the phase diagram agrees with the result of g-ology. On the other hand, in the strong coupling region for V >> | t|, a novel superconducting phase appears both for positive and negative U. We also investigated the charge gap and the spin gap. The results suggest that the superconducting phase extends over the Tomonaga-Luttinger region (without spin gap) and the Luther-Emery region (with spin gap).
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Shuichi Ishida, Sadao Takaoka, Kazuo Murase, Seiichi Shirai, Tadashi S ...
Subject area: Electronic transport in condensed matter.
1994 Volume 63 Issue 4 Pages
1254-1257
Published: April 01, 1994
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Low-temperature transport measurements on a polycrystalline silicon thin-film transistor have been made in order to clarify the role of bandtail states in the grain boundaries. We find a Mott variable-range hopping (VRH) law of the resistance in the barely insulating regime of the metal-insulator transition. At lower temperatures, the resistance crosses over to Efros-Shklovskii VRH with the opening of a soft Coulomb gap. The magnetoresistance (MR) is negative, and its features are qualitatively explained by existing theories of quantum interference effects in VRH. Furthermore, the Hall coefficient remains essentially constant even in the range of thermally activated conduction and Mott VRH.
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Fumiko Yamaguchi, Kiyoshi Kawamura
Subject area: Electronic transport in condensed matter.
1994 Volume 63 Issue 4 Pages
1258-1262
Published: April 01, 1994
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The effect of Coulomb interaction on current noise in a quantum dot not is studied by using the Anderson model. Based on the perturbation expansion in the coupling between the dot and reservoirs in terms of the Keldysh-Green function, current and current noise are computed as functions of applied bias voltage including the infinite-order Coulomb interaction.
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Yoshiaki Saito, Koichiro Inomata, Shinya Uji, Taichi Terashima, Haruyo ...
Subject area: Electronic structure and electrical properties of surfaces, interfaces and thin films.
1994 Volume 63 Issue 4 Pages
1263-1267
Published: April 01, 1994
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The temperature (T) dependence of the resistivity of Co/Cu superlattices having antiferromagnetic (AF) and ferromagnetic (F) interlayer exchange coupling was investigated. The results show that the resistivity versus temperature relationship exhibits a minimum for AF-coupled Co/Cu superlattices while that for F-coupled Co/Cu superlattices dose not. This minimum can be explained by the T dependences of the magnetoresistance (MR) and saturation resistivity, which behave as T
n power laws for T dependence of MR at low temperatures. The powevr laws for T dependences of MR are related to the two-dimensional (2D) behavior due to the weak interlayer exchange coupling and to the T dependence of the magnetization.
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Akiharu Miyanaga, Yasumasa Hasegawa, Hidetoshi Fukuyama
Subject area: Superconductivity.
1994 Volume 63 Issue 4 Pages
1268-1272
Published: April 01, 1994
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Ground states of the two-dimensional t-t'-J model with one and two holes in 4× 4 sites (with periodic boundary conditions) are studied numerically. Using a Lanczos algorithm, we calculate the ground-state energy and momentum distribution, and the phase diagram in the plane of J/t and t'/t is presented. The momentum distribution for J/t=0.25 is compared with the Fermi surface obtained in the mean-field theory. It is shown that the t'/t dependences of the momentum distribution are consistent with the mean-field approximation, although there are quantitative differences between them.
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Yoshihiko Nonomura, Masuo Suzuki
Subject area: Magnetic properties and materials.
1994 Volume 63 Issue 4 Pages
1273-1276
Published: April 01, 1994
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The ground-state phase diagram of the J
1-J
2 model is investigated on the basis of cluster-effective-field approximations. Following our previous studies on the S=1/2 frustrated XXZ chain, classical magnetic order parameters such as the Néel and collinear ones, and the columnar dimer order parameter are analyzed using periodic-boundary clusters. Within these approximations, classical magnetic order is stable in the whole parameter region.
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Yusuke Kato, Akihiro Tanaka
Subject area: Magnetic properties and materials.
1994 Volume 63 Issue 4 Pages
1277-1280
Published: April 01, 1994
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We study the S=1 quantum spin chain with bond alternation Η=∑
i (1-(-1)
iδ )S
i· S
i+1 by the density matrix renormalization group method recently proposed by White (Phys. Rev. Lett. 69 (1992) 2863). We find a massless point at δ
c=0.25 ± 0.01. We also find the edge states in the region δ <δ
c under the open boundary condition, which disappear in the region δ >δ
c. At the massless point, the spin wave velocity v
s is 3.66± 0.10 and the central charge c is 1.0± 0.15. Our results indicate that a continuous phase transition occurs at the massless point δ =δ
c accompanying breaking of the hidden Z
2× Z
2 symmetry.
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Jiro Kitagawa, Naoya Takeda, Hiroshi Sawa, Masayasu Ishikawa
Subject area: Magnetic properties and materials.
1994 Volume 63 Issue 4 Pages
1281-1284
Published: April 01, 1994
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We have found a new compound CePd
3.8Al
7.2 which crystallizes in the tetragonal BaCd
11-type structure. We report the results of the low-temperature specific heat and magnetic susceptibility measurements. The compound did not exhibit any long-range magnetic order down to about 0.5, K. The value of specific heat divided by temperature is strongly enhanced and reaches 6, J/mole· K
2 at the lowest temperature. This confirms that CePd
3.8Al
7.2 is one of the heaviest electron systems.
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Isao Harada, Akio Kotani
Subject area: Optical properties and condensedmatter spectroscopy and other interactions of matter with particles and radiation.
1994 Volume 63 Issue 4 Pages
1285-1288
Published: April 01, 1994
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We propose a mechanism for circular magnetic X-ray dichroism (CMXD) in a pre-edge region of the Fe K-edge in rare-earth iron garnets, within a cluster approximation. The pre-edge absorption is assumed to be dominated by the electric-dipole transition from 1s states to 4p states mixed with 3d states of Fe ions through the hybridization between these orbitals and 2p orbitals of nearest-neighbor O ions. Considering the different symmetries and the different spin orientations for Fe ions at the tetrahedral (T
d) site and at the octahedral (O
h) site, we calculate CMXD for both cases based on T
d and O
h iron-oxygen clusters. It is found that CMXD is a manifestation of the combined effect of the spin-orbit coupling and the spin polarization in the 3d orbitals. The result is discussed in connection with experimental observations.
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Aurea Espinosa, Jorge Fujioka
Subject area: Mathematical methods in physics.
1994 Volume 63 Issue 4 Pages
1289-1294
Published: April 01, 1994
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In this communication the Painlevé-Weiss (PW) analysis is applied to Hirota-Satsuma-type equations, and the hydrodynamic foundation of such equations is presented. It is found that among all the equations of this kind, only the original Hirota-Satsuma eq., and the equation due to Ablowitz, Kaup, Newell and Segur, possess the PW property.
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Shozo Takeno, Kazunari Hori, Kazushi Ohtsuka, Shigeo Homma
Subject area: Mathematical methods in physics.
1994 Volume 63 Issue 4 Pages
1295-1310
Published: April 01, 1994
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An analytical study is made to seek intrinsic nonlinear-mode solutionsto the d-dimensional sine-lattice (SL) equation\begin{equation}∑
i J
i {sin[u(n+ e
i)-u(n)]- sin[u(n)-u(n - e
i)]}-[∂
2u(n)/∂ t
2]=(λ /2) sin[2u(n)]\end{equation}with λ >0 or λ =0 in the form u(n)=2 tan
-1[f(k · n-ω t)/g( K· n-{Ω}t)] with κ =(κ
1, , κ
2, · · ·, , κ
d)(κ =k, , K), where f and g are trigonometric or hyperbolic functions. Approximate analytical solutions for moving and stationary anharmonic localized modes and vortexlike modes (d>2) are obtained for | k
i| << 1 and | K
i| << 1. For λ =0, exact static vortexlike mode solutions exist provided the k
i's and the K
i's satisfy certain specific conditions. For d=1, numerical experiments are performed to confirm the existence of the asymptotically exact moving anharmonic localized modes in the SL equation for λ =0.
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Kazuaki Nakayama, Takeshi Iizuka, Miki Wadati
Subject area: Classical and quantum physics: mechanics and fields.
1994 Volume 63 Issue 4 Pages
1311-1321
Published: April 01, 1994
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The curve lengthening equation is a geometric model where the normal velocity U of the curve is a linear functional of the curvature κ, that is, U=-κ +c (c is a constant). Exact solutions for the curve lengthening equation are found. They include generalizations of the Saffman-Taylor finger. The spiral solutions and their pitches are also discussed.
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Dipak Ghosh, Jaya Roy, Supriya Chatterji, Madhumita Basu, Argha Deb
Subject area: Nuclear reactions and scattering: specific reactions.
1994 Volume 63 Issue 4 Pages
1322-1324
Published: April 01, 1994
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Three-proton correlations in 400, GeV/c with AgBr nuclei have been studied in this paper in the Monte-Carlo background and search for short range dynamical correlations has been made. It is interesting to observe that strong correlations exist in both backward and forward hemisphere in p-AgBr emulsion where in case of π-AgBr interaction at 350, GeV/c correlations exist only in backward hemisphere and there is the evidence of strong correlation.
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Keiji Kosaka
Subject area: Electronic structure of atoms and molecules: theory.
1994 Volume 63 Issue 4 Pages
1325-1336
Published: April 01, 1994
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As an efficient method for rapid calculation of electronic states of atoms and ions, a new approach is proposed. In this method, the electron density is determined by a local scale change to a reference density which can easily be evaluated. A series of calculations are made for Ar-isoelectronic sequence and several rare gas like atoms by using the reference densities with inter-electronic interactions disregarded. A detailed numerical examination indicates that the present method, in spite of its simplicity, yields good approximate solutions for the electronic states of atoms and ions. In fact, the results of the present method are in good agreement with those of the self-consistent field. The agreement is particularly good in the case of highly ionized atoms, indicating the usefulness of the method in ion physics.
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Haruhiko ITO, Taro ITO, Tsutomu Yabuzaki
Subject area: Atomic and molecular collision processes and interactions.
1994 Volume 63 Issue 4 Pages
1337-1344
Published: April 01, 1994
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We propose an efficient method of collisional transfer of transverse magnetic moment between different kinds of atoms using the spin-locking technique. Demonstrating experiments with a rotating or an oscillating rf field are carried out on a
85Rb--
133Cs vapor, and the transfer of a large amount of the transverse magnetic moment is observed when the amplitude H
1 of the rf field is comparable to the static magnetic field strength H
0. The H
1-dependence of the transfer, in the case of the oscillating rf field, is not simple, because of the Bloch-Siegert shift and associated resonance effects. The transfer of the transverse magnetic moment under the strong rf field is numerically analyzed with the Bloch equations for
85Rb and
133Cs coupled through spin-exchange collisions.
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Minoru Takeda, Kazu Nishigaki
Subject area: Mechanics, elasticity, and rheology.
1994 Volume 63 Issue 4 Pages
1345-1350
Published: April 01, 1994
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The extension of liquid oxygen meniscus in magnetic fields has been systematically measured in various fields up to 5, T at temperatures of 65.3, K and 77.1, K. On the basis of the interfacial equation for magnetic fluid, experimental data obtained are analyzed quantitatively. It is found that the deformation of the meniscus can be determined by the balance between the magnetic normal stress and capillary pressure, which act in opposite direction at the interface.
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S. G. TAGARE
Subject area: Fluid dynamics.
1994 Volume 63 Issue 4 Pages
1351-1357
Published: April 01, 1994
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Finite amplitude Rayleigh-Benard Convection in a rotating fluid havebeen investigated when the Prandtl number is large (σ=O(1/ε ) >> 1). In this limit of the Prandtl number, Hopf bifurcation is absent. The time-dependent one-dimensional Landau-Ginzburg equation was discussed near the onset of stationary convection (supercritical cusp bifurcation) in this limit. The steady-state solution of the Landau-Ginzburg equation, which describes the nonlinear behaviour of the convection, was obtained.
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M. S. Ganagi, A. V. Gopalakrishna
Subject area: Fluid dynamics.
1994 Volume 63 Issue 4 Pages
1358-1364
Published: April 01, 1994
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This work deals with the effects of weak nonlinearity and weak dissipation on a linear wave in relativistic gasdynamics. Using perturbation and asymptotic expansions, a relativistic analogue of generalised one-dimensional Burgers' equation of classical gasdynamics is derived to describe far-field description of the wave. Steady state solution is presented for strict one-dimensional case.
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Yoshiomi Kondoh, Tetsuya Sato
Subject area: The physics of plasmas and electric discharges.
1994 Volume 63 Issue 4 Pages
1365-1377
Published: April 01, 1994
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A theoretical investigation on self-organization theories ofdissipative MHD plasmas is presented to derive three groups oftheories that lead to the same relaxed state of \
abla ×B=λ B, in order to find more essential physicalpicture embedded in self-organization phenomena due to nonlinear anddissipative processes. Comparisons among all of the theories treatedand derived here suggest that a theory standing upon spectrumspreadings and selective dissipations of eigenmodes for thedissipative operator -\
abla × η j and leading toself-organized relaxed states of \
abla × η j=α B/2 with the minimum dissipation rate is the most agreeable to various results obtained by experiments and by 3-D MHD simulations reported so far.
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Masanori Inui, Kenji Maruyama, Shin"ichi Takeda, Shigeru Tamaki, ...
Subject area: Structure of liquids and solids; crystallography.
1994 Volume 63 Issue 4 Pages
1378-1385
Published: April 01, 1994
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The structure factors of amorphous Se at room temperature have been obtained by X-ray and neutron diffraction with sufficient accuracy. Although the coincedence of both structure factors is excellent, a clear difference has been found between X-ray and neutron diffraction results. The ion-electron correlation and valence electron distribution functions were evaluated from this difference. The obtained electron distribution function shows a broad peak at the distance around 1.0, Å and the peak has a shoulder around 1.6, Å. These may correspond to the distribution of the lone pair electrons and the covalent bonded electrons around a central Se ion, respectively.
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Hiroshi Harashina, Shin–ichi Shamoto, Katsuaki Kodama, Masatoshi ...
Subject area: Lattice dynamics and crystal statistics.
1994 Volume 63 Issue 4 Pages
1386-1395
Published: April 01, 1994
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Energies of several in-plane phonons have been measured as a functionof temperature T up to about 500, K in the highest case, forcrystals of YBa
2Cu
3O
6.6 (T
c ~= 53, K) andYBa
2Cu
3O
6.9 (T
c ~= 90, K), in which the magnitudes of the transport anomalies are very much different. For a phonon mode in the rather narrow q-region near the zone boundary, or for a mode well characterized by the dimerization type motion of nearest neighbor Cu atoms in the CuO
2 planes, the T-dependence of the phonon-energy is larger for the former crystal than the latter one, suggesting that the T-dependence is stronger for samples with larger transport anomalies.
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Yoshihiro Ishibashi
Subject area: Equations of state, phase equilibria, and phase transitions.
1994 Volume 63 Issue 4 Pages
1396-1399
Published: April 01, 1994
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The successive phase transitions in hexagonal BaTiO
3 is discussedon the basis of the Landau-type free energy function, putting theemphasis on the transition between the intermediate phase II and thelowest temperature phase III. It is pointed out that to induce thephase III with the space group P2
1 the twelveth order term in theorder parameters, transforming under the symmetry operations as thebases of the two-dimensional E
2u representation of the 6/mmm group, is required.
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Haruya Shiba, Masanobu Haraguchi, Masuo Fukui
Subject area: Surfaces and interfaces; thin films and whiskers (structure and nonelectronic properties).
1994 Volume 63 Issue 4 Pages
1400-1405
Published: April 01, 1994
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We have experimentally measured the propagation length L of surface plasmon polaritons propagating along an air-copper and an air-copper on a CaF
2 film interfaces by using a CO
2 laser of wavelength 10.6, μ m. It is found that the CaF
2 film produces a change in the dielectric constant of copper and leads to a decrease of L. It is also shown that L varies with the evaporation speed of the copper film. In order to know the effect of surface roughness on L in the visible region, where various SP experiments have been carried out, we have investigated a roughness effect on the SP propagating along an air-silver interface at wavelength of 0.6328, μ m.
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Yoshiaki Ono, Tamifusa Matsuura, Yoshihiro Kuroda
Subject area: Electron states in condensed matter.
1994 Volume 63 Issue 4 Pages
1406-1421
Published: April 01, 1994
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Properties of the heavy-fermion valence-fluctuating compounds leadingto insulating ground states (called Kondo insulators) are investigatedtheoretically by using the U-infinite degenerate lattice Andersonmodel in the auxiliary boson representation. The model is treatedwithin the approximation including terms of the leading order in theexpansion w.r.t. inverse of the spin-orbit degeneracy(1/N-expansion) under the strict local constraints guaranteeingequivalence of the bosonic version to the original U-infinitemodel. The results are compared with the experimental observations onthe possible candidates for Kondo insulators. Differences betweenKondo insulators and charge transfer type insulators now paid muchattention as the mother systems for the high-T
c superconductors are briefly discussed on a unified basis within the model described above.
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Akimasa Sakuma
Subject area: Electron states in condensed matter.
1994 Volume 63 Issue 4 Pages
1422-1428
Published: April 01, 1994
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The spin-polarized band calculations including spin-orbit interactionfor τ -phase (L1
0) MnAl have been performed with LMTO-ASAmethod in the frame of LSD. It has been predicted that the MnAl has amagnetic moment of 2.4, μ
B with a help of the tetragonaldistortion from cubic B2 to L1
0 structure. The magnetocrystallineanisotropy energy (MAE) is obtained as (0.26 ± 0.01) meV/f.u. Thisleads to 1.5 × 10
6, J/m
3 for magnetic anisotropy constant which is comparable to the measured value -- 10
6, J/m
3. The dependence of the MAE on axial ratio c/a also reflects the influence of the tetragonal distortion, that is, the MAE shows drastic change from negative to positive at the vicinity of c/a=0.7071 which corresponds to cubic B2 lattice. For larger value of c/a, MAE decreases with increasing c/a and goes into negative again for c/a>1.2.
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Masanori Matoba, Shuichiro Anzai, Atsushi Fujimori
Subject area: Electron states in condensed matter.
1994 Volume 63 Issue 4 Pages
1429-1440
Published: April 01, 1994
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The M 2p core-level XPS peaks of doped elements inNi
1-xM
xS are observed at the binding energies of M in“M
2S
3” rather than those of “MS” below and above thenonmetal-metal transition temperature (T
t), indicating thatthe M atom are ionized to M
3+ and acts as shallow donorimpuritites. Below T
t the T
1/2 contribution withnegative sign to the thermoelectric power (S) is superimposed on theusual degenerate semiconductive contribution with positive sign. Itovercomes the latter contribution above a concentration (x
c). The value of x
c increases in the order of M=Ti, V andCr. These results indicate that the T
1/2 contribution to Scomes from variable range hopping through the localized states formednear E
F within the narrow charge-transfer gap of theparent NiS. Above T
t the sign of S is negative in the electron-doped Ni
1-xM
xS as well as in the hole-doped Ni
1-xS, suggesting that they have the Fermi surface topology.
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Takashi Nishikawa, Jun Takeda, Masatoshi Sato
Subject area: Electronic transport in condensed matter.
1994 Volume 63 Issue 4 Pages
1441-1448
Published: April 01, 1994
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Transport properties of La
2-xSr
xCuO
4, YBa
2Cu
3O
6+x andBi
1.6Pb
0.5Sr
1.9-yLa
yCu
1.05O
z have beenstudied over wide temperature regions. Drastic temperature variationsof the Hall coefficients R
H found in the underdoped region ofthe hole carriers suggest that there exists a crossover-like change ofthe electronic state above room temperature. Temperature dependence ofother transport properties studied at high temperatures is alsodiscussed in relation to this anomalous behavior of R
H. Theseresults elucidate the formation process of the abnormal metallic stateof high-T
c oxides at low temperatures, the existence of which characterizes the metal-insulator transition of the Cu-oxide system as a new-type Mott-Hubbard transition.
View full abstract
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Morio Suzuki, Kazunori Komorita, Masamitsu Nagano
Subject area: Superconductivity.
1994 Volume 63 Issue 4 Pages
1449-1454
Published: April 01, 1994
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The tunnel conductances were measured for the Ag--SiO--BaPb
0.75Bi
0.25O
3 junctions at 4.2, K under magnetic fields of 0, 0.62, 1.24, 2.17 and 3.41, T. The coupling strength factor, 2Δ/k
BT
c is found to be equal to 3.6 and in a weak coupling regime. From the magnetic field dependence of tunnel conductance at V=0, mV, the second critical magnetic field H
c is estimated as 4.2, T at 4.2, K. It is found that the large value of tunnel conductance at zero bias voltage is brought by a lifetime effect of BaPb
0.75Bi
0.25O
3 and a leak current and that taking into account the leak current, the present tunnel conductance characteristics can be explained in the framework of BCS theory.
View full abstract
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Yutaka Itoh, Kazuyoshi Yoshimura, Tomohiko Onomura, Hiroshi Yasuoka, Y ...
Subject area: Superconductivity.
1994 Volume 63 Issue 4 Pages
1455-1464
Published: April 01, 1994
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We report the temperature dependence of the planar
63Cu(2)nuclear spin-spin relaxation rate for high-T
c Cu oxidesuperconductors YBa
2Cu
3O
6.98 (T
c -- 92, K), LaBa
2Cu
3O
6.93 (T
c -- 92, K) andY
2Ba
4Cu
7O
14.95 (T
c-- 60, K), includingthe previous report for YBa
2Cu
4O
8 (T
c--82, K). The Gaussian decay rate 1/
63T
G below T
cshows a slight decrease but remains enhanced as above T
c. Asecondary reduction of 1/
63T
G forYBa
2Cu
3O
6.98 and LaBa
2Cu
3O
6.93 has alsobeen observed below about 30, K. We associate this with a change inthe character of the superconducting order parameter. We conclude thatCooper pair of the high-T
c superconducting state is basically in a d-wave gap state.
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Hiroki Goto, Yuhei Natsume
Subject area: Superconductivity.
1994 Volume 63 Issue 4 Pages
1465-1473
Published: April 01, 1994
Released on J-STAGE: October 01, 1999
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The formulation of strong coupling theory for superconductivity in the ultra-high magnetic field is made in the expression of Dyson's equation for the case where electrons are confined only in a few Landau levels. The set of self-consistent equations is proposed in the procedure of Eliashberg theory. Further, results of numerical calculation for the 2-dimensional system performed by the use of Frölich-type potential are discussed. In the dependence of the critical temperature T
c on the field, the convex-structures appear whose peaks correspond to the half-filling in Landau levels. For the ultra-high field where electrons occupy only the ground Landau level, T
c increases with increasing the field. However, it has the tendency to be suppressed by the effect of the retardation for the interaction. On the contrary, the renormalization coefficient increases more abruptly. These behaviors are characteristic features shown clearly in the present calculation.
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Fumihiro Matsukura, Yuuichi Tazuke
Subject area: Magnetic properties and materials.
1994 Volume 63 Issue 4 Pages
1474-1485
Published: April 01, 1994
Released on J-STAGE: October 01, 1999
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In order to understand spin freezing properties, ac-susceptibility χ
ac and relaxation of thermoremanent magnetization (TRM) were measured on an Ising spin glass Fe
0.05TiS
2 in zero and non-zero fields. Analysis of χ
ac above the spin glass freezing temperature shows that a rectangular distribution of spin relaxation times is appropriate and the temperature dependence of the average spin relaxation time follows the power law. The waiting time effects on the relaxation of TRM below the freezing temperature can be interpreted by a hierarchical many-valley structure. These results are consistent with Sherrington-Kirkpatrick model's prediction that the spin glass freezing is a phase transition in both zero and non-zero fields.
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Masayuki Itoh, Ikuomi Natori, Satoshi Kubota, Kiyoichiro Motoya
Subject area: Magnetic properties and materials.
1994 Volume 63 Issue 4 Pages
1486-1493
Published: April 01, 1994
Released on J-STAGE: October 01, 1999
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Magnetic properties of La
1-xSr
xCoO
3 (0 ≤ x ≤ 0.5) have been studied by magnetization measurements in low magnetic fields. It has been found that there exist spin-glass (0
3+ and Co4+ and the antiferromagnetic one between like spins.
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Takuhiro Ogawa, Yoshikazu Suzumura
Subject area: Magnetic properties and materials.
1994 Volume 63 Issue 4 Pages
1494-1501
Published: April 01, 1994
Released on J-STAGE: October 01, 1999
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Treating the periodic Anderson model with the electron-phonon (e-p) interaction in the mean field theory, we examine the insulating state in DCNQI-Cu salts as the function of both the temperature and the e-p coupling constant. By extending the work [J. Phys. Soc. Jpn. 61 (1992) 3322] to the case where the e-p interaction at the Cu site is added, it is shown that the phase transition into the coexistent state of charge density and spin density is accompanied by the large jump of their amplitudes in addition to the hysteresis.
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Hitoshi Sugawara, Tsuyoshi Yamazaki, Junya Ito, Masahiro Takashita, Ta ...
Subject area: Magnetic properties and materials.
1994 Volume 63 Issue 4 Pages
1502-1507
Published: April 01, 1994
Released on J-STAGE: October 01, 1999
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We have grown single crystals of CeRh
2 and CeIr
2 by a tri-arc Czochralski pulling method. Electrical properties including the de Haas-van Alphen effect are presented.
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Yoshitaka Kasamatsu, Kenichi Kojima, Tadamiki Hihara
Subject area: Magnetic properties and materials.
1994 Volume 63 Issue 4 Pages
1508-1517
Published: April 01, 1994
Released on J-STAGE: October 01, 1999
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The hyperfine (hf) fields at the nuclei of N, Ge, Tl, V and Fe impurities in ferromagnetic GdZn and GdCd have been measured by NMR and Mössbauer methods. The results, together with the reported ones, nearly complete the systematics of the hf fields at sp and 3d impurities in GdZn(Cd). The hf fields at 4sp, 5sp and 6sp impurities are always negative, exhibiting a similar variation with increasing the impurity valence. The trend of the hf fields at 3d impurities shows local moment contributions to the hf field at the middle of the 3d series, indicating finite local moments on Mn and Fe impurities. These results are found to resemble the systematics of the hf fields at impurities in Gd and are qualitatively explained by the theory of the hf field developed for Fe and Ni hosts.
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Sung Won Yun, Hitoshi Sugawara, Junya Ito, Masahiro Takashita, Takao E ...
Subject area: Magnetic properties and materials.
1994 Volume 63 Issue 4 Pages
1518-1529
Published: April 01, 1994
Released on J-STAGE: October 01, 1999
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We have measured the electrical resistivity, Hall coefficient, thermoelectric power, magnetic susceptibility, magnetization, specific heat, magnetoresistance and de Haas-van Alphen (dHvA) oscillation of UPd
3 to clarify the magnetic and Fermi surface properties. A phase transition, which occurs at about 4.5, K, is most likely related to the antiferromagnetic ordering because the magnetic specific heat shows a T
3 dependence below 2, K. About ten different dHvA branches ranging from 1.8 × 10
5, Oe to 7.5 × 10
7, Oe have been observed. From the angular dependence of dHvA frequency, UPd
3 is found to consist of the closed spherical Fermi surfaces and multiply-connected ones. The cyclotron masses are light, ranging from 0.5m
0 to 3.6m
0, which indicate the localized f electron character.
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Toshiya Inami, Kazuhisa Kakurai, Hidekazu Tanaka, Mechthild Enderle, M ...
Subject area: Magnetic properties and materials.
1994 Volume 63 Issue 4 Pages
1530-1538
Published: April 01, 1994
Released on J-STAGE: October 01, 1999
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Magnetic excitations of CsMnI
3, a quasi-one-dimensional Heisenberg antiferromagnet with S=5/2, have been measured by means of inelastic neutron scattering. Magnetic excitations in the low temperature phase are in good agreement with the predictions of the conventional linear spin-wave theory. In particular, in accordance with the linear spin-wave theory, we found three separate modes at Q=(0, , 0, , 1) instead of a threefold degenerate mode as seen in CsNiCl
3 (S=1). It confirms that the spin dynamics of the integer spin value system are very different from those of the half-integer spin value system, even in their three-dimensionally ordered phase. Magnetic excitations in the intermediate phase have been also studied and it is found that the excitations were similar to those in the low temperature phase, except some overdamped intensities at certain reciprocal points. These intensities can be associated to the slow rotational motions of the spins around the c-axis.
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Fumihisa Suzuki, Naokazu Shibata, Chikara Ishii
Subject area: Magnetic properties and materials.
1994 Volume 63 Issue 4 Pages
1539-1547
Published: April 01, 1994
Released on J-STAGE: October 01, 1999
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The Green's function formalism proposed by Kondo and Yamaji for low-dimensional spin systems with S=1/2 has been extended to the cases of S>1/2. We apply this formalism to the study of one- and two-dimensional Heisenberg ferromagnets over the whole temperature range. It is shown that our theory can reproduce the correct results obtained by the high-temperature expansion method. On the other hand, the results at low temperatures are similar to those of the modified spin-wave theory, which is considered to predict the low-temperature properties of such systems rather correctly. The gross behaviors of the calculated thermodynamic quantities of ferromagnetic Heisenberg chains agree with those obtained by the exact diagonalization method.
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Yoshiya Adachi, Masayoshi Ohashi, Takejiro Kaneko, Motoyoshi Yuzuri, Y ...
Subject area: Magnetic properties and materials.
1994 Volume 63 Issue 4 Pages
1548-1559
Published: April 01, 1994
Released on J-STAGE: October 01, 1999
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Rhombohedral Cr
2Se
3 is an antiferromagnetic compound with antiferromagnetic AF(L) phase below 38, K (=T
t) and the antiferromagnetic AF(H) one between 38, K and 45, K (=T
N). Neutron diffraction studies for rhombohedral Cr
2Se
3 are carried out at temperatures from 6, K to 77, K. The results show that the magnetic structures of AF(L) and AF(H) phase are a non-collinear and collinear antiferromagnetic structures, respectively, with the monoclinic magnetic unit cell. It was found that Cr moments at the a-sites are frustrated in the AF(H) phase.
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Isao Watanabe
Subject area: Magnetics resonances and relaxations in condensed matter; MÖssbauer effect.
1994 Volume 63 Issue 4 Pages
1560-1571
Published: April 01, 1994
Released on J-STAGE: October 01, 1999
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The magnetic properties of La
2-xM
xCuO
4 (M=Ba, , Sr) for 0 ≤ x ≤ 0.08 have been investigated from 1.5, K to 300, K by the nuclear quadrupole resonance (NQR) of
139La (I=7/2). The electrical quadrupole relaxation process of
139La in La
2CuO
4 is dominant above 50, K in spite of the existence of the internal field at the La site due to the antiferromagnetic ordering of Cu-moments. At low temperature, the magnetic relaxation process becomes dominant. From the divergence of the nuclear relaxation rate, T
1-1, of
139La, we obtain the magnetic phase diagram which consists of two distinct magnetic phases for 0 < x < 0.05. The internal field at the La-site changes discontinuously at T
C* at which the temperature dependence of T
1-1 shows a peak. This change can be interpreted by decrease of the transferred hyperfine fields from Cu spins through the apical oxygen of the CuO
6 octahedron below T
C*.
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Katsuhiko Fujii
Subject area: Dielectric properties and materials.
1994 Volume 63 Issue 4 Pages
1572-1579
Published: April 01, 1994
Released on J-STAGE: October 01, 1999
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The ferroelectric phase transition of hydrogen-bonded crystal KDP is studied under a consideration that the electric polarization is brought by tetrahedral radicals PO
4 which are described by orientational rotators with 6 directions and protons mediate interaction between the neighboring PO
4 radicals. The isotope effect is explained by assuming the difference of rotator-proton coupling constants between KDP and DKDP, without the introduction of tunnelling. The configurational energies for 4 protons around a PO
4 radical are derived, and from the above assumption the mass dependence of energy levels is obtained against the Slater theory.
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Mieko Takagi, Shigeo Suzuki
Subject area: Dielectric properties and materials.
1994 Volume 63 Issue 4 Pages
1580-1589
Published: April 01, 1994
Released on J-STAGE: October 01, 1999
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X-ray diffraction topographic studies on the procedure of polarization reversal of ferroelectric thiourea and on the change in the domain configuration of NaNO
2 near the Curie temperature T
c have been made. Polarization reversal of thiourea takes place via an intermediate state which is domain-wall-like in structure. This procedure is the same as the case of NaNO
2. On the topographs of NaNO
2 taken at the temperatures near T
c width of the domain walls become wider on approaching to T
c, and at the ferro-antiferro phase boundaries all domains are eroded by the broadened domain walls. The results of the present study together with our previous X-ray topographic studies on NaNO
2 and on thiourea suggest that the domain walls, the intermediate states of polarization reversal and the modulated incommensurate phases above T
c resemble in structure.
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Yukikuni Akishige, Hiroki Takahashi, Nobuo Mori, Etsuro Sawaguchi
Subject area: Dielectric properties and materials.
1994 Volume 63 Issue 4 Pages
1590-1594
Published: April 01, 1994
Released on J-STAGE: October 01, 1999
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The dielectric constant ε
c along the c-axis of hexagonal BaTiO
3 has been measured from 5, K to 300, K as a function of hydrostatic pressure p up to 4, GPa. The hexagonal to orthorhombic transition point T
0 (222, K at 10
5, Pa) decreases at a rate of 34, K/GPa and vanishes at pressures above p
c=3.4, GPa; the T
0 vs p curve is well represented by an equation of T
0=a(p
c-p)
1/2 over the whole pressure range. While, the ferroelectric phase transition point T
C (77, K at 10
5, Pa) initially increases and then decreases only slightly with increasing pressure; interestingly, the dielectric anomaly at T
C disappears at pressures above 1, GPa. Another lattice instability like a quantum paraelectricity seems to exist at low temperatures. Some discussions are presented for the mechanism of the phase transitions.
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Hiroyuki Uehara, Masaru Komukae, Toshio Osaka, Yasuharu Makita
Subject area: Dielectric properties and materials.
1994 Volume 63 Issue 4 Pages
1595-1600
Published: April 01, 1994
Released on J-STAGE: October 01, 1999
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The complex dielectric constant of N
2H
5Al(SO
4)
2 · 12H
2O along the cubic [100] direction ε
* was measured in a frequency range between 10, kHz and 1, GHz. The critical slowing-down phenomenon of polarization was observed above the transition temperature 164.5, K (T
C). The experimental result was analyzed on the basis of the dielectric formula which represents the sum of two independent relaxators characterized by relaxation times τ
1 and τ
2. The static dielectric constant of one relaxator, ε
1S, obeys the Curie-Weiss law with the Curie constant C
1=1.75 × 10
2, K and the paraelectric Curie temperature T
01=148, K, while that of the other, ε
2S, hardly depends on temperature. The relaxation time τ
1 can be well explained by the relation τ
1=τ
01 · T/(T-T
01) with τ
01=(h/k
BT) · exp (ΔF
1/k
BT), and the activation free energy was estimated to be ΔF
1=1.51× 10
-20, J just above T
C.
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