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Masaki Goda, Tsuneyasu Okabe, Hiroaki Yamada, Michisuke Kobayashi
Subject area: Mathematical methods in physics.
1994 Volume 63 Issue 8 Pages
2841-2844
Published: August 01, 1994
Released on J-STAGE: October 01, 1999
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The distribution p(x, t) of time-developing Cartesian component of particle displacement, x=x(t)-x(0), starting from δ-function is studied extensively in a superionic conductor AgI in a classically mesoscopic regime using the method of molecular dynamics calculation. The distribution law is modified from that of the Gaussian process, and is found to have the form p(x, t)∝ exp {-ax
β /t
α }, (a>0, 0 ≤ α ≤ 1, 0 < β ≤ 2), in a thermal equilibrium state. Despite of this generalized distribution law, the mean square displacement ‹ r
2› , (t)∝ t
2α /β seems to be t-linear, i.e., 2α /β ≅ 1, in the molten and/or α phase. At the melting point or the superionic transition point, two different distributions of this type seem to compete with each other.
View full abstract
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Yasunori Ohkuma, Tsutomu Takahashi, Kiyomitsu Suzuki, Yasuyuki Nogi
Subject area: Kinetic and transport theory of fluids; physical properties of gases.
1994 Volume 63 Issue 8 Pages
2845-2848
Published: August 01, 1994
Released on J-STAGE: October 01, 1999
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Even when rotational instability observed in a field-reversed-configuration plasma is suppressed by a multipole field, the confinement property of the plasma is not always improved. Plasma stabilized by a quadrupole field shrinks axially with time and its particle confinement time τ
N becomes shorter than that of nonstabilized plasma. The reduction of τ
N is large for the quadrupole field (m=2) and slight for the hexapole (m=3) and octupole (m=4) fields. A simple model reveals that the pertubation of the magnetic field on the separatrix by the multipole field takes a finite value for m=2 and approaches zero for m>2. This suggests that the distortion of the magnetic field at the ends of the separatrix is responsible for the degradation of confinement.
View full abstract
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Yositake Takane
Subject area: Electron states in condensed matter.
1994 Volume 63 Issue 8 Pages
2849-2852
Published: August 01, 1994
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Conductance fluctuations in superconductor-normal metal-superconductor junctions are studied at zero temperature. It is shown that the amplitude of the fluctuations is no longer characterized by the universal value, of order of e
2/h, but generally depends on the sample size and the phase relaxation length L
φ . In the particular cases where the sample size is much smaller than L
φ , we find that an enhancement of the fluctuations greater than the order of e
2/h can be expected to arise. It is ascribed to a manifestation of the large fluctuation in the level density, which is caused by confinement of quasiparticles in the normal-metal region due to Andreev reflection.
View full abstract
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Toshiro Takabatake, Yasuomi Maeda, Taku Konishi, Hironobu Fujii
Subject area: Electron states in condensed matter.
1994 Volume 63 Issue 8 Pages
2853-2856
Published: August 01, 1994
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We have synthesized quaternary compounds UT
2B
2C (T=Ni and Rh) and ThT
2B
2C (T=Ni, Rh and Pt) which crystallize in the LuNi
2B
2C-type structure. The uranium compounds with 5f electrons exhibit strong magnetism; UNi
2B
2C orders antiferromagnetically at 218, K and URh
2B
2C orders ferromagnetically at 185, K. In contrast, the nonmagnetic analogues ThNi
2B
2C and ThPt
2B
2C undergo superconducting transitions at 6.5 and 6.7, K, respectively.
View full abstract
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Hazuki Kawano, Hideki Yoshizawa, Yutaka Ueda
Subject area: Electron states in condensed matter.
1994 Volume 63 Issue 8 Pages
2857-2861
Published: August 01, 1994
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As one of the members of the ABO
3-type pseudoperovskite oxide family, Y
1-xCa
xVO
3 exhibits an insulator-metal transition upon a change in the dopant calcium ion concentration x. We have reinvestigated the magnetic structure of the parent compound YVO
3 with use of the neutron scattering technique. YVO
3 orders at T
N1=118 K with the so-called C-type antiferromagnetic structure, but changes to the G-type antiferromagnetic structure at T
N2-- 77 K through a first order transition with lattice distortion. These spin structures differ from those of an early study by Zubkov { et al}. (Sov. Phys.-JETP 39 (1974) 896). The static moment which contributes to the magnetic long range order is extrapolated to be less than 1.6 μ
B at T=0 K. This value of the static moment is more than 20% smaller than 2.0 μ
B expected for a localized spin system with S=1, indicating the existence of spin fluctuations in a Mott insulator YVO
3.
View full abstract
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Kazuaki Iwasa, Ken Holst Andersen, Miwako Takahashi, Hironobu Ikeda
Subject area: Electron states in condensed matter.
1994 Volume 63 Issue 8 Pages
2862-2865
Published: August 01, 1994
Released on J-STAGE: October 01, 1999
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Recently, a high-resolution inelastic neutron spectrometer equipped with a superconducting magnet has been installed at the pulsed spallation neutron source (KENS) at the National Laboratory for High Energy Physics (KEK). For the first experiment using this spectrometer system, we investigated inelastic neutron scattering from diluted Heisenberg magnetic systems, RbMn
cMg
1-cF
3 (c=0.10 and 0.15) at 1.5, K with applied magnetic fields. Magnetic excitations in finite-size clusters were observed due to the low concentration of spins localized at the manganese ions. The observed spectra were compared with calculations which were performed by diagonalizing the Hamiltonian. Extending the number of spins in a cluster up to five, good agreement with calculations was obtained for both excitation energies and scattering intensities.
View full abstract
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Shoji Yamamoto, Seiji Miyasato
Subject area: Electron states in condensed matter.
1994 Volume 63 Issue 8 Pages
2866-2869
Published: August 01, 1994
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A world-line quantum Monte Carlo method is employed to study the dispersion relation of an S=1 antiferromagnetic Heisenberg chain. An imaginary-time correlation function is evaluated on a transformed two-dimensional Ising system, and the low-lying energy spectrum is extracted from that. This straightforward method produces a dispersion relation which agrees well with the previous results.
View full abstract
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Hitoshi Ohta, Seisaku Imagawa, Hiroyuki Ushiroyama, Mitsuhiro Motokawa ...
Subject area: Electron states in condensed matter.
1994 Volume 63 Issue 8 Pages
2870-2873
Published: August 01, 1994
Released on J-STAGE: October 01, 1999
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Magnetization and submillimeter wave ESR measurements have been performed on single crystals of CuGeO
3 using a pulsed high magnetic field. Magnetization jumps are observed at 12.8, 12.5 and 13.5, T for a-, b- and c-axes, respectively, at 4.2, K. The temperature dependences of the linewidth and the integrated intensity of the ESR signal are discussed in connection with the conventional spin-Peierls systems, and the excitation gap against the magnetic field is estimated when the field is applied along the a-axis. ESR has been observed in the magnetic phase above the critical field H
c and the g-values have different values from those in the spin-Peierls phase. The origin of this difference is discussed.
View full abstract
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Teruo Ono, Nobuyoshi Hosoito, Teruya Shinjo
Subject area: Electron states in condensed matter.
1994 Volume 63 Issue 8 Pages
2874-2877
Published: August 01, 1994
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Fe-Ag granular alloys were fabricated by simultaneous deposition in ultrahigh vacuum. Magnetoresistance and Mössbauer effect were measured. Magnetoresistance change 100(ρ (H=0)-ρ (H=50 kOe))/ρ (H=0) of about 30{%} was observed in the Fe
15Ag
85 sample at 5 K, which did not saturate even at 50 kOe. From Mössbauer spectroscopy, it was found that about 18{%} of Fe moments in this sample did not align with the applied field direction even in the magnetic field of 40 kOe.
View full abstract
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Kenji Ikushima, Jun Kikuchi, Hiroshi Yasuoka, R. J. CAVA, Hidenori TAK ...
Subject area: Electron states in condensed matter.
1994 Volume 63 Issue 8 Pages
2878-2881
Published: August 01, 1994
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The normal state of LuNi
2B
2C, one member of a new family of intermetallic superconductors, has been probed by
11B NMR. The
11B nuclear spin-lattice relaxation rate, 1/T
1, and the Knight shift have been measured between 20 and 350, K. It was found that 1/T
1T is more enhanced at low temperatures than the Knight shift, which has a weak temperature dependence. This result indicates that antiferromagnetic spin fluctuations contribute considerably to 1/T
1T at low temperatures in the normal state.
View full abstract
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Yoshihiro Ishibashi, Minoru Fokui
Subject area: Materials science.
1994 Volume 63 Issue 8 Pages
2882-2885
Published: August 01, 1994
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The temporal variation of the average velocity of cars in the Biham-Middleton-Levine (BML) model is studied. The equations which govern the temporal variation of the car velocities for various densities of cars are derived. By utilizing these equations, the final average velocity is approximately obtained for most self-organized states.
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Masato Hisakado, Takeshi Iizuka, Miki Wadati
Subject area: Mathematical methods in physics.
1994 Volume 63 Issue 8 Pages
2887-2894
Published: August 01, 1994
Released on J-STAGE: October 01, 1999
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Nonlinear short pulse propagations in birefringent optical fiber are studied. A new nonlinear evolution equation is presented, which is a hybrid of the coupled nonlinear Schrödinger equation and the coupled derivative nonlinear Schrödinger equation. As a solution for the coupled hybrid nonlinear Schrödinger equation, solitary waves (pulsed electric fields) propagating at a constant speed are obtained.
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Toshio Hasegawa, Kazuhiro Hikami, Miki Wadati
Subject area: Mathematical methods in physics.
1994 Volume 63 Issue 8 Pages
2895-2901
Published: August 01, 1994
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We construct the solutions of the su(2) trigonometric Knizhnik-Zamolodchikov (KZ) equation based on the Babujian's ''off-shell Bethe ansatz'' method. We show that the quasi-classical limit of the Bethe ansatz equation including the ''unwanted term'' for the inhomogeneous XXZ lattice reduces to the trigonometric KZ equation.
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Ryutaro Kanno, Akio Ishida
Subject area: Mathematical methods in physics.
1994 Volume 63 Issue 8 Pages
2902-2908
Published: August 01, 1994
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By means of Feynman's path integral, it is found that a quantum-mechanical path that contributes to the path integral has the property of the baker's mapping. The determinability of direction of a velocity at any time is determined by the mapping.
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Kazuyuki Tanaka, Yositake Takane, Hiromichi Ebisawa, Tohru Morita
Subject area: Mathematical methods in physics.
1994 Volume 63 Issue 8 Pages
2909-2918
Published: August 01, 1994
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The square approximation in the cluster variation method is formulated for the t-J model. By using this approximation, we study the phase transition to a magnetically ordered state in the three-dimensional t-J model on a cubic lattice. The Néel order is shown to appear near half-filled region.
View full abstract
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Sadao Isogami, Makoto Katori, Mitsugu Matushita
Subject area: Mathematical methods in physics.
1994 Volume 63 Issue 8 Pages
2919-2929
Published: August 01, 1994
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We studied competing directed percolation (CDP) to confirm the validity of Matsushita and Meakin's theory also for the case that an entire pattern is self-similar and not compact, while its individual clusters are self-affine. Critical values of the bond concentration p
c and values of the various scaling exponents of CDP in 2-- 6 dimensions were estimated by simulations. The present result shows that Matsushita and Meakin's theory is valid for CDP in any dimension. It is also found that the estimated values of the scaling exponent of the cluster-size distribution τ are different from those of ordinary directed percolation.
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V. B. Magalinsky, Masaki Hayashi, Honorio Vera Mendoza
Subject area: Mathematical methods in physics.
1994 Volume 63 Issue 8 Pages
2930-2935
Published: August 01, 1994
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We formulate the Feynman's variational principle for a density matrix by means of Bohm-Madelung representation using Lagrange variables, which appear to be dynamical invariants of phase flux with sources on the ends of trajectories. With a linear parametrization in invariants for the flux the variational problem can be formulated as the extended principle of least action in which the functional variables appear to be trajectories of the center and the dispersion of the renormalized vacuum wave packet, which is reduced at the ends of the trajectories. Approximating the extended action in terms of bilocal frequency, we derive an explicit expression which provides the exact result for the linear systems and, in general case, proper semi-classical correction and correct asymptotics for the ground state. We examine the effect of spontaneous symmetry breaking on the coordinate distribution as well.
View full abstract
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Mustafa Abdusalam Nasr, Tauseef Ahmad, M. Irfan
Subject area: Nuclear structure.
1994 Volume 63 Issue 8 Pages
2936-2941
Published: August 01, 1994
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An attempt is made to investigate the characteristics of relativistic particles produced in the collisions of silicon nuclei with emulsion nuclei at 4.5, A, GeV/c. Results reveal that the mean values of pseudorapidity, η, and dispersion D(η ), ‹ η › and ‹ D(η )› exhibit decreasing trends with increasing ‹ N
s› values.
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Satoshi Sasaki, Yasuyuki Ohkouchi, Shuichi Takamura, Takako Kato
Subject area: Nuclear structure.
1994 Volume 63 Issue 8 Pages
2942-2954
Published: August 01, 1994
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Effective emission and ionization rate coefficients of carbon atom in plasmas are obtained with a collisional radiative model considering 31 states including the ground state and the excited states with the principal quantum number n≤ 4. Population dynamics of carbon atom in an ionizing plasma are discussed in the plasma parameter range of 10
1≤ n
e≤ 10
17, cm
-3, 1≤ T
e≤ 100, eV. The effective emission and ionization rate coefficients of carbon atom are discussed in relation to the population dynamics and summarized for the applications such as the carbon impurity flux measurement, the electron temperature measurement and the investigations of carbon impurity transport in the edge and divertor plasmas in fusion devices.
View full abstract
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Norio Watanabe, Kiyomi Kutsumi, Osamu Sano
Subject area: Electricity and magnetism: fields and charged particles.
1994 Volume 63 Issue 8 Pages
2955-2963
Published: August 01, 1994
Released on J-STAGE: October 01, 1999
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An irregular motion of a mercury drop in a petri dish filled with HNO
3 and K
2Cr
2O
7 solutions is studied experimentally. Larger mercury globules are extended and broken into smaller droplets, while smaller ones translate or rotate randomly in an otherwise quiescent fluid owing to the non-uniform distribution of the surface tension associated with chemical reaction. The translating mercury drop shows a peculiar form like a croissant with broad convex surface perpendicular to the direction of motion. Although the direction and magnitude of the movement of the drop change randomly, the average speed is almost independent of its size if it satisfies a certain criterion. The fluctuation of velocity shows a power spectrum proportional to 1/f
α , where α is nearly equal to 1 in fairly wide frequency range. A simple analysis on the basis of the Stokes approximation is made, which explains the relation between the average speed and the drop size.
View full abstract
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Shigeo Kida
Subject area: Electricity and magnetism: fields and charged particles.
1994 Volume 63 Issue 8 Pages
2964-2973
Published: August 01, 1994
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Linear stability of thermal convection driven by self-gravity and internal heat source in a rotating sphere is analyzed by a singular perturbation method at large Taylor number Ta. The neutral disturbance localized in the radial direction generally tilts from that direction. The radial structure of such oblique disturbance takes a Gaussian form spreading over length-scale of O(Ta
-1/12). The localness of disturbance becomes weaker as the tilt angle decreases. In the special case of uniform heat source and linear gravity force it is proved that the critical Rayleigh number Ra
c* should be attained by such disturbances that have vanishing tilt angle (F. H. Busse, J. Fluid Mech. 44 (1970) 441). Since, however, no disturbance without tilting can be localized in the radial direction, this critical Rayleigh number is nominal. At the Rayleigh number slightly greater than the critical (Ra
*-Ra
c*=O(Ta
-1/9)), the disturbance tilts only slightly (by O(Ta
-1/18)) and spreads over length-scale of O(Ta
-1/9) in the radial direction.
View full abstract
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Yukio kaneda, Greg Holloway
Subject area: Electricity and magnetism: fields and charged particles.
1994 Volume 63 Issue 8 Pages
2974-2985
Published: August 01, 1994
Released on J-STAGE: October 01, 1999
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Nonlinear interactions in geostrophic, beta-plane turbulence induce frequency shifts in Rossby wave propagation. A statistical closure theory shows that the shifts are of systematic sign and can be quite large compared with the bare Rossby frequency. This is also supported by direct numerical simulations. Under certain conditions, the closure equations yield a simple approximation for the shifts. A physical interpretation of the shifts is given by a model that includes oscillating random sweeping and strain of large eddies.
View full abstract
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Akihide Takeda, Nobuaki Ikuta
Subject area: Kinetic and transport theory of fluids; physical properties of gases.
1994 Volume 63 Issue 8 Pages
2986-2992
Published: August 01, 1994
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The transverse diffusion coefficient D
T and the conventional expression D
V for electrons in CF
4 are compared. The ratio of D
V and D
T reaches 6 at the maximum. The cause of such large differences between D
V and D
T are discussed from their definitions and also in relation to the cross sections of CF
4. When inelastic collisions make the velocity distribution highly anisotropic, D
V defined in velocity space is not appropriate to use in place of D
T even as an approximate expression.
View full abstract
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Kanemitsu Katou, Hiroshi Mamada
Subject area: Kinetic and transport theory of fluids; physical properties of gases.
1994 Volume 63 Issue 8 Pages
2993-2998
Published: August 01, 1994
Released on J-STAGE: October 01, 1999
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The mode structure of global drift waves in tokamaks, which are not localized by magnetic shear and density inhomogeneity, is investigated in the framework of fully two-dimensional problems. We obtain the analytically explicit, two dimensional expressions for the electrostatic potential of global drift waves, distinguishing between the weak and strong regimes with respect to the strength of torodicity (the ratio of the density scale length to the major radius). The former is found to have an up-down asymmetry of the phase function on the cross-section of the torus, while the latter has that of both the phase function and the amplitude.
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Toshihiko Dote, Masatoshi Shimada
Subject area: Kinetic and transport theory of fluids; physical properties of gases.
1994 Volume 63 Issue 8 Pages
2999-3002
Published: August 01, 1994
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To date, there have been mainly two approaches for the study of the transition from free to ambipolar diffusion of charged particles. First, by means of transport equations with a constant ratio approximation (CRA) assuming that the spatial distributions of electrons and ions have the same form, an effective diffusion coefficient characterizing diffusive flow of charged particles has been calculated. Second, without assuming CRA, the distribution of electrons in particular has been solved and the effective diffusion coefficient has been defined from an effective diffusion length which is proportional to the distance from the central point to the absorbing boundary. Here, it is shown that the effective diffusion coefficient with CRA is generally more significant than that without CRA.
View full abstract
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Roberto A. Clemante, Loren C. Steinhauer
Subject area: Kinetic and transport theory of fluids; physical properties of gases.
1994 Volume 63 Issue 8 Pages
3003-3007
Published: August 01, 1994
Released on J-STAGE: October 01, 1999
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A fluid model allowing for plasma resistivity and anisotropic temperatures, for describing edge-layer and jets in field-reversed configurations, is presented. Jet velocity can be predicted in terms of drops in parallel and perpendicular temperatures, from the separatrix to the throat, and the edge-layer broadness should depend on plasma conductivity. Comparison with experimental measurements suggests that the conductivity should be an order of magnitude lower than classical.
View full abstract
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Tadao Ishii
Subject area: Structure of liquids and solids; crystallography.
1994 Volume 63 Issue 8 Pages
3008-3013
Published: August 01, 1994
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Sound attenuation in superionic conductors due to the density-wave non-associated mechanism is extensively studied by means of the relaxation mode theory. It is confirmed that the contribution of non-diffusive modes is quite large comparing with that of diffusive modes.
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Masahiko Higuchi, Hiroshi Yamagami, Akira Hasegawa
Subject area: Electron states in condensed matter.
1994 Volume 63 Issue 8 Pages
3014-3025
Published: August 01, 1994
Released on J-STAGE: October 01, 1999
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On the basis of the itinerant-electron model for the 4f electrons, the energy band structure, especially the Fermi surface, is calculated for the paramagnetic heavy-electron compound CeRh
2, which has the low-temperature electronic specific heat coefficient of 20, mJ/K
2, mol and the Kondo temperature of 400, K, by a self-consistent symmetrized relativistic APW method with the exchange and correlation potential in a local-density approximation. The Fermi surface consists of two hole spheres and a hollow electron sphere with small windows, all of which are centered at the Γ point in the Brillouin zone. The spherical property of the Fermi surface explains qualitatively well the behavior of the de Haas-van Alphen frequency branches measured recently by Sugawara { et al}. Candidates for the frequency branches missing in the experiment are suggested.
View full abstract
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Rikio Settai, Terutaka Goto, Shinichi Sakatume, Yong Seung Kwon, Takas ...
Subject area: Electron states in condensed matter.
1994 Volume 63 Issue 8 Pages
3026-3035
Published: August 01, 1994
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The acoustic de Haas van Alphen effect of the low carrier compound CeSb has been measured by a homemade dilution refrigerator. The heavy hole orbit of β
4 in the ferromagnetic phase has been clearly observed. The cyclotron effective mass of β
4 under the magnetic field along [001] direction was 4.3m
0. The angular dependence of the cross-sectional area of β
4 is well explained by the band calculation based on the p-f mixing model. Some aspects of the electron-strain interaction obtained by the oscillation intensity of the elastic constant are discussed.
View full abstract
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Nguyen Ai Viet, Hiroshi Ajiki, Tsuneya Ando
Subject area: Electron states in condensed matter.
1994 Volume 63 Issue 8 Pages
3036-3047
Published: August 01, 1994
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A lattice instability toward in-plane Kekulé and out-of-plane distortions is studied in metallic carbon nanotubes in both k· p approximation and tight-binding model. The k· p model Hamiltonian is given by Dirac's relativistic equation in the presence of distortion. The resulting gap equation is solved analytically in the presence of an Aharonov-Bohm magnetic flux through the cross section of nanotube, leading to the conclusion that the in-plane and out-of-plane distortions cannot coexist. A tight-binding model gives results in excellent agreement with k· p results and justifies the k· p model Hamiltonian.
View full abstract
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David P. Hurly, Michael Coey, Toyotaka Osakabe, Yutaka Kuroiwa, Masahu ...
Subject area: Electron states in condensed matter.
1994 Volume 63 Issue 8 Pages
3048-3052
Published: August 01, 1994
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Inelastic neutron scattering experiments on polycrystalline Gd(Fe
11Ti) and its isostructural nitride Gd(Fe
11Ti)N
1-δ yield a direct measurement of the exchange field (B
ex) acting at the unique Gd site in the ThMn
12-type structure. B
ex is 255(8), T in the parent compound but nitrogen occupation of the interstitial sites above and below the rare-earth along the c-axis reduces B
ex in the nitride to 220(8), T. These values are in agreement with those deduced from the Curie-temperature using molecular field theory and they are consistent with inelastic neutron scattering data on other Gd
1-xFe
x intermetallic compounds.
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Akimasa Sakuma
Subject area: Electron states in condensed matter.
1994 Volume 63 Issue 8 Pages
3053-3058
Published: August 01, 1994
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The spin-polarized band calculations including spin-orbit interaction for L1
0-FePt and CoPt ordered alloys have been performed with LMTO-ASA method in the frame of local spin density functional approximation. It has been shown that strong uniaxial magnetic anisotropy of both alloys is brought about by a large spin-orbit coupling of Pt atom and a strong hybridization of Pt d bands with highly polarized Fe (Co)d bands. The obtained magnetocrystalline anisotropy energy (MAE) is about 16× 10
6, J/m
3 for FePt and 9× 10
6, J/m
3 for CoPt. It is also found that both MAE's have a trend of increase with increasing axial ratio c/a in the vicinity of measured c/a. This can be regarded as being associated with the behavior that the MAE's decrease with increasing band filling.
View full abstract
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Masatoshi Imada
Subject area: Electron states in condensed matter.
1994 Volume 63 Issue 8 Pages
3059-3077
Published: August 01, 1994
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Critical properties of transitions between a variety of quantum fluids and the Mott insulator are examined in terms of the transition to an incompressible state. In one dimension, they show universally common properties each other irrespective of the statistics, components and the interaction of particles. In two dimensions, they show qualitative differences originated from the differences in the nature of the quantum fluid. It is useful to categorize the singularity at the Mott transition into two types, namely, one characterized by the charge mass divergence and the other by the vanishment of the carrier number. This difference originates from the number of components. Its variety is further explored by examining various cases such as strongly correlated fermions, hard core bosons and boson t-J models. Critical properties to other incompressible states such as spin gap states and the fractional quantum Hall state are also discussed from the same viewpoint. Relevance of our analyses to the understanding of normal state properties in high-T
c cuprates and other transition metal oxides is discussed.
View full abstract
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Eisuke Iguchi, Woo Hwan Jung
Subject area: Electron states in condensed matter.
1994 Volume 63 Issue 8 Pages
3078-3086
Published: August 01, 1994
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Electrical transports of LaFe
1-xTi
xO
3 (x≤ 0.10) containing ligand holes (3d
5L) were investigated by dielectric properties, ac and dc conductivities. A dielectric relaxation peak appeared with the activation energy which increased from 0.49, eV to 0.56, eV with increasing the amount of Ti ions. A thermal activation in the intensity of the peak was observed with the activation energy of 0.02, eV for LaFeO
3 and 0.05, eV for Ti-doped specimens. These energies corresponded well to those obtained in dc conductivities. Compensation of holes by electrons introduced by substitutions of Ti
4+ for Fe
3+ was confirmed. The ac conductivity was found to obey an equation of σ (ω )=Aω
s, ω being the angular frequency. There were three temperature ranges in the plots of β (=1-s) vs T; the low temperature range where β ~= 0, the intermediate range where Pike's theory holds and the high temperature range where holes can hop over large energy barriers. These behaviours have been discussed in terms of small polarons of ligand holes.
View full abstract
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Katsuki Amemiya, Kiyoshi Kawamura
Subject area: Electron states in condensed matter.
1994 Volume 63 Issue 8 Pages
3087-3097
Published: August 01, 1994
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The Hall resistance is studied by solving the Schrödinger equation for electrons in the presence of a magnetic field. The boundary element method (BEM) has been employed to solve the Schrödinger equation with complicated boundary conditions. The Hall resistance anomalies in low magnetic fields are discussed from the view points of the wave mechanics. The quasi-bound states in the Hall junction, which causes sharp dips in the plot of the Hall resistance as a function of the magnetic induction in high magnetic fields, is studied in terms of the wave functions. It is found that the quasi-bound states are similar to some of the eigenstates confined in a disk with a hole. From this similarity, the quasi-bound state which is responsible for each dip is identified.
View full abstract
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Satoshi Kashiyama, Masao Koyanagi
Subject area: Electron states in condensed matter.
1994 Volume 63 Issue 8 Pages
3098-3106
Published: August 01, 1994
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The proximity effect in the Au layer of NbC
0.3N
0.7/Au bilayer was studied by low-temperature scanning tunneling microscopy/spectroscopy (LT-STM/S). The conductance spectra were obtained for various Au thickness. The theoretical conductance spectra were calculated on the basis of a quasi-classical theory and by introducing a probability distribution of tunneling in momentum-space. Good agreements between the theoretical and experimental conductance spectra are obtained by taking the effective STM tip radius as a fitting parameter. Low energy excitations below gap voltage observed in the conductance spectra are explained by the total reflections at the NbC
0.3N
0.7/Au interfaces.
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Manabu Ikebe, Hiroyuki Fujishiro, Tomoyuki Naito, Koshichi Noto
Subject area: Electron states in condensed matter.
1994 Volume 63 Issue 8 Pages
3107-3114
Published: August 01, 1994
Released on J-STAGE: October 01, 1999
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A method to measure the thermal diffusivity α and the conductivity κ under an identical experimental setup has been developed and α and κ of Bi-2223 oxide superconductor have been measured quasi-simultaneously. The results are analyzed on the basis of the BRT and Tewordt-Wölkhausen theory. The simultaneous measurement makes it possible to estimate the specific heat C and the Debye temperature Θ
D, as well as to separate the electron and phonon contributions to the diffusivity. The simultaneous measurement also provides a useful check on the reliability and the consistency of the analyses.
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Kiwamu Oda, Takayuki Kumada, Kiyohiro Sugiyama, Noriaki Sato, Takemi K ...
Subject area: Electron states in condensed matter.
1994 Volume 63 Issue 8 Pages
3115-3121
Published: August 01, 1994
Released on J-STAGE: October 01, 1999
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The high field magnetization of antiferromagnetic heavy Fermion material UPd
2Al
3 is investigated up to 50, T. A clear metamagnetic step is observed at 18, T along the a-axis for 1.3, K. The angular dependence of the step-magnetization shows a large anisotropy in the ac-plane and the spin system can be described by the XY-spin model except for very small anisotropy in the c-plane. The observed step-magnetization is explained by introducing the model that the heavy Fermion state is broken at the critical field by the magnetic field and the exchange interaction is modified by the change in the carrier density.
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Hiroko Aruga Katori, Atsuko Ito
Subject area: Electron states in condensed matter.
1994 Volume 63 Issue 8 Pages
3122-3128
Published: August 01, 1994
Released on J-STAGE: October 01, 1999
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The de Almeida-Thouless (AT) line for Ising spin-glasses has been studied by using the typical Ising spin-glass Fe
xMn
1-xTiO
3 with x=0.41, 0.50, 0.55 and 0.57. The spin-glass transition temperatures in fields H between 2.0, Oe and 4.0× 10
4, Oe, T
SG(H), were determined by the dc-magnetization measurements. The field dependence of T
SG(H) is well described by the equation H=A
exp[1-T
SG(H)/T
SG(0)]
α for small fields. It is found that the exponent α is very close to 3/2 predicted by the AT theory. Moreover, it is shown that the coefficient A
exp obtained for Fe
xMn
1-xTiO
3 is in much better agreement with the value given by the Ising Sherrington-Kirkpatrick model than any other systems, which shows the validity of the AT theory for Ising spin-glasses. This result evidences the existence of the spin-glass transitions in finite fields for Ising systems.
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Shinji Yuasa, Hideki Miyajima, Yoshichika Otani
Subject area: Electron states in condensed matter.
1994 Volume 63 Issue 8 Pages
3129-3144
Published: August 01, 1994
Released on J-STAGE: October 01, 1999
JOURNAL
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Magnetic properties of FeRh
1-xPt
x system with body-centered cubic and body-centered tetragonal (bct) structures were studied by means of X-ray diffractometry, magnetometry and Mössbauer spectroscopy, and the phase diagram in a temperature-composition plane was determined. With substituting Pt for Rh, the axial ratio c/a was increased and the bct phase was stabilized. With increasing temperature, the bct alloys with 0.72
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