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Katsurou Hanzawa
Subject area: Electron states in condensed matter.
1999 Volume 68 Issue 4 Pages
1063-1066
Published: April 01, 1999
Released on J-STAGE: October 01, 1999
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It is pointed out that the hyperfine field at B nuclei in CeB
6 is attributed to the dipole-dipole interaction of the nuclear moment with the magnetic moments of Ce ions and the transferred hyperfine interaction due to the 2s and 2p states of B ion hybridized with the 4f states of Ce ions. Both contributions have the same order of magnitude, and account for the hyperfine fields in the antiferro-quadrupolar ordering phase II and the paramagnetic phase I.
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Atsushi Tsuruta, Akito Kobayashi, Ken Deguchi, Yoshiaki Ono, Tamifusa ...
Subject area: Electron states in condensed matter.
1999 Volume 68 Issue 4 Pages
1067-1070
Published: April 01, 1999
Released on J-STAGE: October 01, 1999
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We investigate the Fermi liquid in the infinite-U degenerate Anderson lattice using expansion from the limit of large spin-orbital degeneracy N. By collecting all diagrams up to O(N
-2), we show that the imaginary part of the self-energy of the conduction electrons is given by a form proportional to (ω-μ)
2+π
2T
2. We also show that the Luttinger sum rule holds up to O(N
-1). This implies that the literal 1/N-expansion procedure correctly describes the Fermi liquid in the U-infinite Anderson lattice.
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Nobukatsu Yoshida, Yukio Tanaka, Junichiro Inoue, Satoshi Kashiwaya
Subject area: Superconductivity.
1999 Volume 68 Issue 4 Pages
1071-1074
Published: April 01, 1999
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A theory of tunneling conductance inferromagnetic-metal / insulator / triplet-superconductorjunctions is presented for unitary and non-unitary spin tripletpairing states which are promising candidates for thesuperconducting pairing symmetry of Sr
2RuO
4.As the magnitude of the exchange interaction in the ferromagnetic metalis increased, the conductance for the unitary pairingstate below the energy gap is reduced in contrast to that forthe non-unitary pairing state.This is due to the fact that the retro-reflectivity inthe Andreev reflection for unitary pairing state is brokendue to the influence from the exchange interaction.
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Ryuta Yagi, Shun–ichi Kobayashi, Youiti Ootuka
Subject area: Superconductivity.
1999 Volume 68 Issue 4 Pages
1075-1077
Published: April 01, 1999
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We observed a superconductor-insulator (S-I) transition in single small Josephson junctions by changing the tunneling resistance of normal tunneling junctions connected in parallel.
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Minoru Nohara, Masanobu Isshiki, Fumiko Sakai, Hidenori Takagi
Subject area: Superconductivity.
1999 Volume 68 Issue 4 Pages
1078-1081
Published: April 01, 1999
Released on J-STAGE: October 01, 1999
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The quasiparticle density of states (DOS) in the vortex state has been probed by specific heat measurements under magnetic fields (H) for clean and dirty s-wave superconductors, Y(Ni
1-xPt
x)
2B
2C and Nb
1-xTa
xSe
2. We find that the quasiparticle DOS per vortex is appreciably H-dependent in the clean-limit superconductors, while it is H-independent in the dirty superconductors as expected from a conventional rigid normal electron core picture. We discuss possible origins for our observations in terms of the shrinking of the vortex core radius with increasing H.
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Hiroyuki Yamase, Hiroshi Kohno, Hidetoshi Fukuyama, Masao Ogata
Subject area: Magnetic properties and materials.
1999 Volume 68 Issue 4 Pages
1082-1085
Published: April 01, 1999
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In the vicinity of hole density 1/8, La-based high-T
c cuprates exhibit long-range order of incommensurate antiferromagnetism (IC-AF). Motivated by this observation, we explore the possible stabilization of IC-AF ordering due to the existence of static charge density modulation (CDM). We use Ginzburg-Landau free energy based on the mean field theory of the t-J model. We show numerically that three kinds of CDMs, including a stripe pattern, can stabilize static IC-AF ordering. We also argue that such CDMs can cause the saturation of the degree of incommensurability (η) for IC-AF fluctuation as a function of hole density. In our framework, the effects of the low-temperature tetragonal (LTT) structure only appear as a slight increase of η for the stripe pattern.
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Tetsuya Takeuchi, Bernd Becker, Srinivasan Ramakrishnan, Alois A. Meno ...
Subject area: Magnetic properties and materials.
1999 Volume 68 Issue 4 Pages
1086-1089
Published: April 01, 1999
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Unusual magnetic ordering and metamagnetic transition in U
2Rh
3Si
5 were studied by thermal expansion and magnetostriction measurements. Thermal expansion along the three quasi-orthorhombic axes shows discontinuities with an anisotropic strain at the ordering temperature (T
o=25.5 K). The anisotropic strain increases with applied magnetic field but the volume change at T
o becomes smaller opposite to the changes in the lattice length. Magnetostrictions also exhibit sharp and large length changes at the metamagnetic transition, showing the strong magnetostrictive coupling in U
2Rh
3Si
5. The unusual behaviors of the magnetic and electronic properties at this transition could be due to the change in the electronic states arising from the large magnetostrictive effect.
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Takuro Katsufuji, Sang–Wook Cheong, Shigeo Mori, Cheng–Hsu ...
Subject area: Magnetic properties and materials.
1999 Volume 68 Issue 4 Pages
1090-1093
Published: April 01, 1999
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Impurity effects on charge ordering (CO) as well as magnetic ground states in perovskite-type manganites are investigated. We found that the CO state becomes short-ranged with a small amount of impurities, in contrast to the impurity effects on the magnetic ordering without CO, e.g., the ferromagnetic (FM) state or the layered antiferromagnetic state. Such a short-ranged CO may play an important role in the competition between the FM state and the CO state.
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Hitoshi Sugawara, Yuji Aoki, Hideyuki Sato, Nikolay Mushnikov, Tsuneak ...
Subject area: Magnetic properties and materials.
1999 Volume 68 Issue 4 Pages
1094-1097
Published: April 01, 1999
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We have investigated high field magnetization on single-crystalline CeFe
2Ge
2 which is classified as a heavy fermion with a non-magnetic ground state. A clear metamagnetic anomaly, which resembles those reported in CeRu
2Si
2, was observed around 300 kOe for the field along the c-axis. The T
3/2 dependence of the electrical resistivity in a wide temperature range from around 15 K down to 2 K, followed by T
2 dependence at lower temperatures, is apparently similar to that in CeNi
2Ge
2 which is close to a quantum critical point.
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Atsuko Ito, Nai–Li Di
Subject area: Magnetics resonances and relaxations in condensed matter; MÖssbauer effect.
1999 Volume 68 Issue 4 Pages
1098-1101
Published: April 01, 1999
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Properties of the magnetic phase transition of the antiferromagnet FeBr
2 have been studied by measuring low-field dc-magnetizations, ac-susceptibilities and Mössbauer spectra. All quantities measured show anomalous behaviors around and immediately below the Néel temperature T
N. Combining all the results, it is suggested that FeBr
2 transforms from the paramagnetic to antiferromagnetic state through the intermediate domain state which exists in a certain narrow temperature region ΔT just below T
N. From the fact that the spread of ΔT is sample-dependent, we have inferred that the stacking fault of the hexagonal c-layers plays an important role in the formation of the intermediate domain state. A new type of transition process from the paramagnetic to the ordered state is discussed.
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Ming–Fa Lin
Subject area: Dielectric properties and materials.
1999 Volume 68 Issue 4 Pages
1102-1105
Published: April 01, 1999
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The electronic excitations of narrow-gap carbon toroids arestudied within the self-consistent-field approach. The low-frequency excitation spectrumexhibits many peak structures, including a prominent one, which isidentified as the collective excitations. This plasmon is due to thecoherent carrier oscillation on a toroid surface along the longitudinal direction. Whether the low-frequency plasmon exists ina carbon toroid is determined by the energy gap and the threshold excitation energy. It is verysensitive to the changes in longitudinal angular momentum transferand the toroid geometry (radius, width, and chiral angle).
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Yongtang Wu, Mengru Li
Subject area: Mathematical methods in physics.
1999 Volume 68 Issue 4 Pages
1107-1114
Published: April 01, 1999
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The trace formulas for the eigenvalue problem of the Schrödinger system are calculated under the self-adjoint boundary condition, unlocal boundary condition and decaying conditions at ± ∞ .
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Koji Imai, Kimiaki Konno, Hiroshi Kakuhata
Subject area: Mathematical methods in physics.
1999 Volume 68 Issue 4 Pages
1115-1120
Published: April 01, 1999
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By assuming the symmetry group and using the inverse method, we find an integrable system which is constructed from superposition of two hierarchies of integrable equations.We discuss SU(2) and SL(2, R) cases in detail.Furthermore, we present a procedure to construct integrable equations by taking a coefficient in the hierarchies as function of x and t.
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Yasuhiro Fujii, Miki Wadati
Subject area: Mathematical methods in physics.
1999 Volume 68 Issue 4 Pages
1121-1130
Published: April 01, 1999
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The bounded XXZ spin chain is studied. The operator appeared in the q-difference equation discovered by Cherednik is modified into the transfer matrix of the model. Its eigenstate is composed by the vertex operators of the quantum affine algebra. By use of a geometric symmetry called the “turning symmetry” that the spin chain without boundary magnetic fields satisfies, the asymptotic form of the eigenstate is found and the spontaneous magnetization at a boundary is calculated. It is roughly twice as large as that in the half-infinite XXZ spin chain.
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Keiji Saito, Taro Nagao
Subject area: Classical and quantum physics: mechanics and fields.
1999 Volume 68 Issue 4 Pages
1131-1138
Published: April 01, 1999
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We consider a failure of the semiclassical trace formula attributable toresonant periodic orbits and quasi-integrability of the system by using the quantum standard map. We derive Gutzwiller-type semiclassicalexpressions of TrU and TrU
2 for the Floquet operator U, and compare them with quantum rigorous expressions. We demonstratethat the divergence of the formula due to resonant orbits is avoided by making use of the normal forms for the action. For a quasi-integrable case, we confirm that the semiclassical expression is also well modified.
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Beatriz Boechat, Claudette Cordeiro
Subject area: Statistical physics and thermodynamics.
1999 Volume 68 Issue 4 Pages
1139-1142
Published: April 01, 1999
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The mean field renormalization group approach has been used toinvestigate the random mixed spin-1/2 Heisenberg ferromagnet inthe two and three-dimensions. The model can describe an isotropicHeisenberg material doped at random with Ising-like anisotropyimpurity atoms. The critical surfaces are displayed graphically inthe complete parameter space. The behaviours observed by incorporating the effect of randomness in thed=2 and d=3 systems are discussed.
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Riki Kawashima, Ryo Hattada, Hiroshi Isoda
Subject area: Statistical physics and thermodynamics.
1999 Volume 68 Issue 4 Pages
1143-1147
Published: April 01, 1999
Released on J-STAGE: October 01, 1999
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Time series data in ac conductivity at 2, kHz along the c-axis of terbium nitrate crystal with metastable phenomena have been measured at temperatures, -70°C≤ T≤ 20°C, in sequent measuring runs. Non-periodic instability (burst) has been observed at those temperatures, as not in lighter rare earth nitrates. The limit cycles were found in the return map constructed from the time series behavior in unstable non-periodic time domain. Power spectrum densities derived from the data have showed characteristic properties of both broad random peaks and continuous spectrum proportional to 1/f
α (α =0-- 2). Fractal dimensions have been given for the time series data in the stable fluctuated and the unstable non-periodic time domains.
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Munetaka Sasaki, Koji Nemoto
Subject area: Statistical physics and thermodynamics.
1999 Volume 68 Issue 4 Pages
1148-1161
Published: April 01, 1999
Released on J-STAGE: October 01, 1999
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The magnetization is introduced to a hierarchical diffusion model and a relation between the response function and the correlation function is derived to evaluate the zero-field-cooled magnetization (ZFCM) and the thermoremanent magnetization (TRM).It is found that if the correlation of distribution of magnetization (CDM) is weak, the behaviors of ZFCM and TRM are governed by the distribution of the barrier energy.The aging is observed in this case. On the other hand, these behaviors are governed by the strength of CDM if it is strong enough, and the aging is not observed.
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Kazuya Kimura, Ryuji Takaki
Subject area: Mechanics, elasticity, and rheology.
1999 Volume 68 Issue 4 Pages
1162-1167
Published: April 01, 1999
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Behavior of solid particles in 2D fluidized bed was observed. The particles had a shape of circular cylindar and were arranged in a single layer in a narrow channel with liquid flow from below. Particles moved randomly, and formed clusters of various sizes. Their sizes and shapes were measured from video images. At the same time, pressure difference between upstream and downstream sides was measured. Spectra of the timewise variations of those quantities were obtained. Spectra concerned to particle cluster and the pressure difference were found to behave as f
-1 and f
-2, respectively, where f is the frequency. A correlation between the pressure difference and the horizontal cluster width was recognized.
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Kirti Prakash, Naresh Kumar
Subject area: Fluid dynamics.
1999 Volume 68 Issue 4 Pages
1168-1172
Published: April 01, 1999
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The effect of the finite Larmor radius (FLR) and variable gravity force in the thermal instability of Rivlin-Ericksen elastico-viscous fluid in porous medium is considered. It is found that the presence of magnetic field (hence of FLR) and visco-elasticity introduces oscillatory modes, when gravity is increasing upward but oscillatory modes are non-existent in their absence. It is also found that system is stable, when gravity decreases upward. When instability sets in as stationary convection finite Larmor radius have stabilizing effect whereas magnetic field and medium permeability has stabilizing or destabilizing effect under certain conditions. The sufficient conditions for the non-existence of overstability are also found.
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Kyoji Yamamoto, Shinichiro Yanase, Md. Mahmud Alam
Subject area: Fluid dynamics.
1999 Volume 68 Issue 4 Pages
1173-1184
Published: April 01, 1999
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The incompressible viscous steady flow through a curved duct of squarecross-section driven by a pressure gradient along the duct is considered. The rotation of the duct about the centre of the curvature is imposed to investigate the combined effects of rotation (Coriolis force) and curvature (centrifugal force) on the flow.The numerical calculations covering a wide range of rotational speed are carried out for the Dean numbers, D
n, of 400, 642 and 800.When the rotation is in the same as the main flow direction, multiple solutions with 2-cell and 4-cell secondary flow patterns are obtained in case of D
n =400 and 642, while only 4-cell solution is obtained in case of D
n=800. When the rotation is opposite to the main flow direction, the 6-cell secondary flow pattern is obtained for D
n=400, 642 and D
n=800 with increasing the rotational speed gradually.For all cases, the total flux through the duct has a sharp peak, where the 6-cell pattern appears.
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Nobuko Fuchikami, Shunya Ishioka, Ken Kiyono
Subject area: Fluid dynamics.
1999 Volume 68 Issue 4 Pages
1185-1196
Published: April 01, 1999
Released on J-STAGE: October 01, 1999
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A dripping faucet system is simulated. We numerically show that a hanging drop generally has many equilibrium shapes but only one among them is stable. By taking a stable equilibrium shape as an initial state, a simulation of dynamics is done, for which we present a new algorithm based on Lagrangian description. The shape of a drop falling from a faucet obtained by the present algorithm agrees quite well with experimental observations. Long-term behavior of the simulation can reproduce period-one, period-two, intermittent and chaotic oscillations widely observed in experiments. Possible routes to chaos are discussed.
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Byung–Rock Kim, Jin–Seok Jeon, Ho–Young Kwak
Subject area: Fluid dynamics.
1999 Volume 68 Issue 4 Pages
1197-1204
Published: April 01, 1999
Released on J-STAGE: October 01, 1999
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Behavior of a gas bubble trapped under ultrasound was studied by the light scattering method. With fixed frequency of the ultrasound, the stability of bubble motion was investigated by increasing the driving sound pressure. It has been found that a selective bifurcation instead of period doubling occurs when the driving pressure is increased and the bubble gains extreme stability after the cascade occurrence of such bifurcation. It has also been found that very higher harmonic components in the Fourier spectrum of the bubble motion appear at the sonoluminescing regime, the absolute stable condition.
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Takao Yoshinaga
Subject area: Fluid dynamics.
1999 Volume 68 Issue 4 Pages
1205-1207
Published: April 01, 1999
Released on J-STAGE: October 01, 1999
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The behavior of double vortex sheets is examined in the linear analysisfor applying the vortex method to a fluid sheet in a surrounding fluid. The result shows that the flow velocities of the fluid sheet and surrounding fluid are uniquely specified due to the induced velocity on the vortex sheets.Then, the dispersion relations of disturbances on the vortex sheets for the antisymmetric (sinuous) and symmetric (bulge) modes are found to be exactly coincident with those from the potential theory.
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Kohji Yamamoto, Nobuaki Ikuta
Subject area: Kinetic and transport theory of fluids; physical properties of gases.
1999 Volume 68 Issue 4 Pages
1208-1215
Published: April 01, 1999
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A rigorous procedure of the Monte-Carlo simulation for the motion of ions in gases under the electric fields is developed. This procedure is applicable for the ions having arbitrary collision frequencies dependent on the relative speed referred to the gas particles. Test calculations are performed in a model gas consisting of rigid sphere particles at the temperature of 300, K for three ion-neutral mass ratios. The data in good agreement with the corresponding theoretical values under zero field and with the FTI data at several values of reduced electric field verify the validity of this procedure. Fundamental properties of the ion motion in thermal gases are also discussed in relation with the mass ratios.
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Md. Khurshed Alam, A. Roy Chowdhury
Subject area: The physics of plasmas and electric discharges.
1999 Volume 68 Issue 4 Pages
1216-1220
Published: April 01, 1999
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We have analysed the effect of non-thermal electrons on the interaction between the electrostatic ion-cyclotron wave and drift wave, taking into account the low frequency ponderomotive force. It is observed that one of the equation is a generalisation of the famous Hasegawa-Mima form with a non-zero right hand side representing interaction with ion cyclotron wave. In the second part we have treated only the drift wave equation in the non-interacting limit and have obtained exact vortex like solutions. Lastly, the modulational instability of the drift wave is studied in the non-interaction limit, by deriving a non-linear Schrodinger equation.
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Akito Sagisaka, Keisuke Nagashima, Mitsuru Yamagiwa, Tohru Matoba, Hir ...
Subject area: The physics of plasmas and electric discharges.
1999 Volume 68 Issue 4 Pages
1221-1227
Published: April 01, 1999
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The population inversion between n=2 and 1 in hydrogen-like helium is calculated with a non-Maxwellian electron energy distribution in a plasma produced by optical field-induced ionization. Collisional relaxation of the electron energy distribution after passage of the laser pulse is followed by using a non-linear Fokker-Planck equation. In the low density regime the relaxation process plays an important role in limiting the population inversion, because the cold component of the electron distribution is reduced. A significant gain is obtained with a pulse length of less than 30, fs.
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Tatsufumi Nakamura, Tomokazu Kato
Subject area: The physics of plasmas and electric discharges.
1999 Volume 68 Issue 4 Pages
1228-1237
Published: April 01, 1999
Released on J-STAGE: October 01, 1999
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Time evolution of the distribution function of a finite length ion beam propagating in a plasma channel is calculated and the obtained solution is valid for a long enough time to utilize it for an inertial confinement fusion (ICF) driver. In order to obtain the time evolution of the distribution function of the finite length ion beam, we solved the Maxwell-Vlasov equations. And also a profile of a return current which is induced by an electromagnetic interaction between the ion beam and channel plasma is calculated. The return current influences the time evolution of the ion beam and results in nonlinear effects on the Vlasov equation. This nonlinear system is solved using perturbation method with the aid of the operator method in order to avoid secularity in the solution. We applied it to solve two interesting cases; the Gaussian beam model and a hollow beam model. From a numerical estimate of the forces acting on the ion beam, we can see that the beam transport is more feasible with the hollow model than the Gaussian model, because the ion beam diverges more with the latter beam by the radial electric field which is proportional to the radial gradient of the charge density. At the beam tail, the beam tends to shrink in both cases because of the magnetic field, which is induced by the incompleteness of the current neutrality.
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Tetsu Miyamoto
Subject area: The physics of plasmas and electric discharges.
1999 Volume 68 Issue 4 Pages
1238-1258
Published: April 01, 1999
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The steady state and quasi-steady processes of infinite- and finite-width sheet z-pinches are studied. The relations corresponding to the Bennett relation and Pease-Braginskii current of cylindrical fiber z-pinches depend on a geometrical factor in the sheet z-pinches. The finite-width sheet z-pinch is approximated by a segment of infinite-width sheet z-pinch, if it is wide enough, and corresponds to a number of (width/thickness) times fiber z-pinch plasmas of the diameter that equals the sheet thickness. If the sheet current equals this number times the fiber current, the plasma created in the sheet z-pinches is as dense as in the fiber z-pinches. The total energy of plasma and magnetic field per unit mass is approximately equal in both pinches. Quasi-static transient processes are different in several aspects from the fiber z-pinch. No radiation collapse occurs in the sheet z-pinch. The stability is improved in the sheet z-pinches. The fusion criterions and the experimental arrangements to produce the sheet z-pinches are also discussed.
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Takashi Fujikawa, John J. Rehr, Yukihiro Wada, Shin–ichi Nagamat ...
Subject area: Lattice dynamics and crystal statistics.
1999 Volume 68 Issue 4 Pages
1259-1268
Published: April 01, 1999
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We propose approximate methods to handle the thermal spherical wave (SW) effects in single and multiple scattering EXAFS spectra, and also in full multiple scattering XANES spectra. In EXAFS region multiple scattering renormalization is not important, and we apply the path-by-path technique and the separable formulas of the free propagator in angular momentum representation. The single scattering thermal SW EXAFS functions give rise to the phase difference from the PW EXAFS functions. On the other hand in the double scattering EXAFS the thermal SW effects are quite small both in the amplitudes and the phases. In contrast to the EXAFS, it is important to renormalize the full multiple scattering series in XANES analyses. We assume the random phase cancellation for cross products of complicated multiple scattering terms, which enables us to renormalize the multiple scattering series and greatly simplifies the finite temperature XANES formula.
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Sadhna Singh, R. K. Singh, R. Rai, B. P. Singh
Subject area: Equations of state, phase equilibria, and phase transitions.
1999 Volume 68 Issue 4 Pages
1269-1272
Published: April 01, 1999
Released on J-STAGE: October 01, 1999
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We have studied B1-B2 transition and volume collapse in relatively less explored rubidium halides using three body potential model (TBPM) and two body potential model (TWBPM) and found better results with three body potential model. Also, rubidium halides obeyed the universal equation of state of Vinet et al. [Phys. Rev. B 48 (1993) 5891].
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Hiroyuki Mashiyama, Kazuko T. Mashiyama
Subject area: Equations of state, phase equilibria, and phase transitions.
1999 Volume 68 Issue 4 Pages
1273-1276
Published: April 01, 1999
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A model for incommensurate transitions proposed by Chen and Walker [Phys. Rev. B 43 (1991) 5634] has been extended to describe a sub-lattice model which possesses supersymmetry. If a zone boundary mode freezes, a superstructure with supersymmetry can appear and may transform into a superstructure without supersymmetry at lower temperature. Although both superstructures belong to the same space group, the transition is either second or first order one with accompanying a definite anomaly in specific heat and susceptibility.
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Kazuya Saito, Yasuhisa Yamamura, Hiroki Akutsu, Masaru Takeda, Hiromit ...
Subject area: Thermal properties of condensed matter.
1999 Volume 68 Issue 4 Pages
1277-1285
Published: April 01, 1999
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Heat capacity of TTF--TCNQ was measured by adiabatic and chopped-light ac calorimetries below room temperature.A thermal anomaly due to the Peierls transition ofthe TCNQ column was clearly detected around 52 K while that due tothe TTF column (around 48 K) was not detected in both methods.A small but sharp peak due to the first-order transitionat 37 K caused by the phase locking of the CDW's on both columns wasdetected in calorimetry for the first time.Heat capacity of TSF--TCNQ was measured by adiabaticcalorimetry below room temperature.Two steps due to the Peierls transitions on TSF and TCNQ columnswere detected.The absence of the anomaly around 48 K in TTF--TCNQ wasdiscussed through comparison of the thermal anomaliesof two compounds.Standard thermodynamic functions are tabulated.
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Seiji Taki, Tsutomu Kadotani, Shoichi Kai
Subject area: Surfaces and interfaces; thin films and whiskers (structure and nonelectronic properties).
1999 Volume 68 Issue 4 Pages
1286-1291
Published: April 01, 1999
Released on J-STAGE: October 01, 1999
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Systematic observations are carried out for molecular alignments of monolayers of homologous series in cyanobiphenyle (CB) liquid crystals such as 6CB to 12CB on highly oriented pyrolytic graphite (HOPG) substrates using a scanning tunneling microscope. For 6CB the molecular alignments are also observed on molybdenum disulfide substrates (MoS
2) as well as HOPG. In 6CB monolayers, the characteristic structures indicating both properties of a single and double row previously reported are observed. In 7CB, 9CB and 11CB monolayers only the single row property is observed. The monolayer alignments of 8CB, 10CB and 12CB show on the other hand double row characteristics. Thus all the observed aspects clearly indicate the odd-even effect of carbon numbers in an alkyl chain. The morphology of molecular alignments due to the odd-even effect in monolayers of cyanobiphenyl liquid crystals on HOPG are systematically determined. Based on the experimental observation a qualitative model on the molecular alignments of CB liquid crystals is proposed.
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Kazumi Omata, Fumiko Yonezawa
Subject area: Surfaces and interfaces; thin films and whiskers (structure and nonelectronic properties).
1999 Volume 68 Issue 4 Pages
1292-1299
Published: April 01, 1999
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We carry out computer simulationsin order to study the finger instability of a wetting filmflowing down an inclined substrate.By calculating power spectrums of the contact line, we investigate the growth of the fingers.We observe a crossover between a fast growth at early timesand a slow growth at late times, which is in qualitative agreement with experimental results.We show that the fast growth is related withthe flow perpendicular to the direction of the external force, while the slow growth arises from the difference of the film thicknessbetween the tip and trough of a finger.In addition, we present the detailed illustrationof the curly flows of the liquid near and in the fingers, which demonstrates the local behaviors of the instability.
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Hiroshi Yaguchi, Yasuhiro Iye, Tadashi Takamasu, Noboru Miura, Tadao I ...
Subject area: Electronic transport in condensed matter.
1999 Volume 68 Issue 4 Pages
1300-1305
Published: April 01, 1999
Released on J-STAGE: October 01, 1999
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The effects of fast-neutron irradiation on the magnetic-field-induced electronic phase transition in graphite have been investigated; the fast-neutron irradiation introduces lattice defects in graphite, some of which act as acceptors. It has been found that the transition temperature is lowered with increasing concentration of lattice vacancies introduced by neutron irradiation. The suppression of the transition temperature can be interpreted as a manifestation of the pair-breaking effect by charged lattice vacancies, similar to magnetic impurities in a superconductor. This supports the existing theoretical interpretation of the field-induced transition being a density-wave transition.
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Takashi Sugiyama, Nobuo Tsuda
Subject area: Electronic transport in condensed matter.
1999 Volume 68 Issue 4 Pages
1306-1312
Published: April 01, 1999
Released on J-STAGE: October 01, 1999
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Electrical resistivity ρ and the magnetic susceptibility have been measured for CaRu
1-xMn
xO
3 (0≤ x≤ 0.3). The samples are all metallic. The Kondo effect occurred in ρ . The Kondo temperature is about 48, K independent of the Mn concentration, and ρ took a minimum value at 310, K for x = 0.3.Weak ferromagnetic moment and a field cooling effect were induced by the Mn substitution. However, these magnetic behaviors may not stem from a canted antiferromagnetism nor itinerant ferromagnetism which homogeneously prevails in the entire lattice since the occurrence of Kondo effect indicates that some of Mn ions are not involved in a magnetically cooperative state.
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Yukio Yasui, Hisashi Sasaki, Masatoshi Sato, Masashi Ohashi, Yoshiaki ...
Subject area: Electronic transport in condensed matter.
1999 Volume 68 Issue 4 Pages
1313-1320
Published: April 01, 1999
Released on J-STAGE: October 01, 1999
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Transport, thermal and elastic properties under the hydrostatic pressure p up to 21.2, kbar have been studied on the layered compound BaCoS
2, which exhibits the Mott insulator→ metal transition with the Ni-substitution for Co and/or with the application of the external pressure p. By the detailed studies in the p-region proximity to the insulator-metal phase boundary, the existence of the antiferromagnetic metal phase has been established for the present quasi two dimensional electron system. The mechanism of the transition is also discussed.
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Tsuyoshi Yamaguchi
Subject area: Electronic structure and electrical properties of surfaces, interfaces and thin films.
1999 Volume 68 Issue 4 Pages
1321-1330
Published: April 01, 1999
Released on J-STAGE: October 01, 1999
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Electronic states are calculated by the DV-Xα-LCAO method for four model clusters of the pentacene molecule adsorbed on dimer rows of the Si(001)2×1 surface. About 2 electrons transfer from the Si substrate to pentacene molecule. These electrons are loosely localized in the region of the pentacene molecule above the Si dimers. The calculated charge dencities of individual occupied and unoccupied orbitals near the Fermi level are compared with the scanning tunneling microscopy (STM) images. The good reproducibility of the STM images implies that electrons tunnel from/to the eigenstates of the combined system of the adsorbed organic molecule and the Si substrate where the adsorbate molecule is assumed to bond covalently to dangling bonds of Si dimers.
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Takanobu Jujo, Shigeru Koikegami, Kosaku Yamada
Subject area: Superconductivity.
1999 Volume 68 Issue 4 Pages
1331-1339
Published: April 01, 1999
Released on J-STAGE: October 01, 1999
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We study the superconducting transition temperature and the electronic properties of the metallic phase of κ-type (BEDT-TTF)
2X which shows unconventional properties in experiments, on the basis of the third order perturbation theory for a simple effective Hubbard model of a nearly triangular lattice. Appropriate transition temperatures and d
x2-y2symmetry of the gap function are obtained in good agreement with experimental results. We also calculate the transition temperature by the fluctuation-exchange approximation (FLEX) in order to compare the two approaches; FLEX gives higher transition temperatures rather than the perturbation approach. However, it is also found that the vertex corrections, which are ignored in FLEX, have a crucial effect on T
c for strongly frustrated systems. The density of states and the normal self-energy calculated in this perturbation scheme show the nature of the conventional Fermi liquid near the Mott-insulator. Thus, our perturbation approach is applicable to the conventional metallic phase of this compound, while it cannot explain the (pseudo-)spin gap phenomenon which signals the non-Fermi liquid.
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Hideyuki Yoshikawa, Tôru Moriya
Subject area: Superconductivity.
1999 Volume 68 Issue 4 Pages
1340-1344
Published: April 01, 1999
Released on J-STAGE: October 01, 1999
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As a possible explanation for the neutron resonance peak observed in YBa
2Cu
3O
6+x, spin excitons in nearly antiferromagnetic superconductors are studiedon a nearly half-filled 2-dimensional Hubbard model.The dynamical spin susceptibility of the BCS superconductor with a given gap function iscalculated by using the random phase approximation.We study the dispersion and broadening of excitons and find that the peak appears in a limited range of q-space around the antiferromagnetic vector(π, π).We also study how this phenomenon depends on the strength of the on-site interaction U, the amplitude Δ
0 of the d-wave gap function, and the occupation number ‹ n ›.The results seem to be consistent at least qualitatively with the experimental resultson YBa
2Cu
3O
7.It is found that the exciton peak tends to disappear for relatively small values of Δ
0.This might be related with the absence of resonance peak in La
2-xSr
xCuO
4. No spin exciton peak is expected in s- or extended s-wave superconductors.
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Sunao Hamada, Nobuyoshi Hosoito, Teruya Shinjo
Subject area: Magnetic properties and materials.
1999 Volume 68 Issue 4 Pages
1345-1352
Published: April 01, 1999
Released on J-STAGE: October 01, 1999
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To study the micromagnetic structures of the Co(20, Å)/Au(20, Å) multilayer films with perpendicular anisotropy where the quality factor (ratio of perpendicular anisotropy and demagnetizing energy) is below 1, the middle of the selected Co layers of the multilayers was doped with
57Fe probes and the Mössbauer spectra were measured. As the total number of the Co layers, N, is increased, the Fe spin orientation in the Co layers turns from in-plane (N=1 and 2) to out-of-plane (N=30). And for the samples with N=31, the spin orientations were found to be depth-dependent, that is, the spin orientation was closer to the film normal in the middle part of the multilayers than near the surfaces. The depth-dependent demagnetizing fields that originate from the out-of-plane micromagnetic structure of the multilayers for N=31 were estimated from the analysis of the hyperfine field splittings of the spectra. This micromagnetic structure is attributable to an out-of-plane flux closure pattern. The stability of the micromagnetic structures is discussed by estimating the magnetic energy.
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Yoshihiro Ishibashi, Makoto Iwata
Subject area: Magnetic properties and materials.
1999 Volume 68 Issue 4 Pages
1353-1356
Published: April 01, 1999
Released on J-STAGE: October 01, 1999
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Elastic stiffness constants in magnetostrictive alloys of the rare-earth Fe
2 compound family are discussed on the basis of the Landau-type free energy function expressed in terms of magnetization and strain components. It was found that some of elastic stiffness constants become extremely small in the vicinity of tetragonal-rhombohedral phase transition points.
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Shin–hachiro Saito, Motoyoshi Ohaba
Subject area: Magnetics resonances and relaxations in condensed matter; MÖssbauer effect.
1999 Volume 68 Issue 4 Pages
1357-1363
Published: April 01, 1999
Released on J-STAGE: October 01, 1999
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Proton nuclear magnetic resonance has been studied for
1H in the solvent of super-paramagnetic fluid in which fine particles of magnetite, Fe
3O
4, are suspended as colloid. An optical microscope has been used to observe the filamentary agglomeration of colloidal clusters under an applied magnetic field, H
0.The filaments are aligned in the direction parallel to H
0 within a minute after the application of the magnetic field of 1, kOe. An average of local magnetic fields at the positions of
1H is antiparallel to the direction of H
0, and its magnitude depends on the arrangements of filaments. A tentative estimate of the interacting force between a colloidal cluster and a filament has been done by the measurement of the growing velocity of filaments. The force is estimated to be an order of 10
-19 dyne (10
-24, N) under H
0 of 1.1, kOe.
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Osamu Sakai, Ryosuke Shiina, Hiroyuki Shiba, Peter Thalmeier
Subject area: Magnetics resonances and relaxations in condensed matter; MÖssbauer effect.
1999 Volume 68 Issue 4 Pages
1364-1370
Published: April 01, 1999
Released on J-STAGE: October 01, 1999
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Anomalous NMR spectra in phases III and III
′ of CeB
6 are analyzed theoretically by introducing a new type of hyperfine coupling of the
11B nuclei with Ce multipolar moments. It is shown that the observed spectra can be reproduced if we take into account the antiferro-polarization of the T
xyz octupole in addition to the antiferromagnetic order proposed by neutron diffraction experiment (ND). Thus ND and NMR are mutually consistent in phase III, if the octupolar contribution is properly included. The analysis of NMR gives the magnitude of the polarization of the octupolar moment.The present analysis strongly suggests that the antiferro-quadrupolar ordering of Γ
5+ type is playing an important role behind the mysterious 2k antiferromagnetic ordering of phase III.
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Junko Hatori, Kazuhiro Tsuri, Kiyoshi Deguchi, Masaru Komukae, Toshio ...
Subject area: Dielectric properties and materials.
1999 Volume 68 Issue 4 Pages
1371-1375
Published: April 01, 1999
Released on J-STAGE: October 01, 1999
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The complex dielectric constant of (CH
3)
2NH
2H
2AsO
4 was measured in a frequency range between 10 MHz and 13 GHz.Dielectric dispersion was found to be very close to the monodispersive Debye type.The critical slowing-down phenomenon of polarization was observed near the phase transition temperature of 274.5 K ( T
c ).Dielectric constants ε in crystals of (CH
3)
2N(H
1-xD
x)
2(H
1-xD
x)
2AsO
4 system were measured at 100 kHz as functions of temperature.The ferroelectric phase transition temperature increases with increasing deuterium concentration x .The temperature dependence of the relaxation time τ in the paraelectric phase can be well explained by the quasi-one-dimensional dynamic Ising model.The activation energy was estimated to be E
a = 64.3 meV.
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S. M. Hasanuzzaman, Kaoru Iwano, Keiichiro Nasu
Subject area: Optical properties and condensedmatter spectroscopy and other interactions of matter with particles and radiation.
1999 Volume 68 Issue 4 Pages
1376-1383
Published: April 01, 1999
Released on J-STAGE: October 01, 1999
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The infrared and visible spectral shapes of optical absorption in a three dimensional charge density wave (CDW) state of BaBiO
3 (BBO) are theoretically studied by using an extended Peierls-Hubbard model, so as to clarify the direct and indirect exciton effects in this material. For this purpose we introduce the adiabatic approximation for phonons and the Hartree-Fock approximation for inter-electron coulombic interactions. The electron-hole correlation on the Bi atoms and the classical fluctuation of the oxygen sub-lattice coordinates are also taken into account, so as to obtain exciton effects as well as thermal fluctuations of the lattice. The energy splitting due to CDW formation in the 6s band of Bi is found to be very large (2.0, eV), whereas, the minimum gap is much smaller (0.55, eV) than it. This large optical gap appears in the visible region as a dominant peak of the optical conductivity, and it is mainly due to the direct exciton. While the smaller gap appears in the infrared region, and it is due to the indirect exciton.This theory well agrees with the results of recent optical experiments on BaBiO
3.
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Takashi Yamamoto, Hiroyuki Tajima, Jun–Ichi Yamaura, Shuji Aonum ...
Subject area: Optical properties and condensedmatter spectroscopy and other interactions of matter with particles and radiation.
1999 Volume 68 Issue 4 Pages
1384-1391
Published: April 01, 1999
Released on J-STAGE: October 01, 1999
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We systematically study transport and optical properties of charge-transfer salts, (Me
2-DCNQI)
2Li
1-xCu
x (0≤ x≤ 1). The temperature dependence of electrical resistivity exhibits semiconducting behavior at x=0, a metal-semiconductor transition for 0.08≤ x≤ 0.29, and metallic behavior down to 4.2, K for x≥ 0.39. A semiconductor-semiconductor transition is observed around 60, K for x≤ 0.14. The reflectance spectra at room temperature reveal two optical excitations in the infrared region. The first excitation appears in salts with x≠ 0 far below 650, cm
-1. The second excitation is the so-called mid-infrared band, which appears around 3000, cm
-1 for 0≤ x≤ 0.14, and shifts downward for x≥ 0.17. We propose a hypothesis which provides an explanation both for the metallic conduction and for the mid-infrared band in a one-dimensional conductor having a quarter-filled band.
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Takeo Jo, Jean–Claude Parlebas
Subject area: Optical properties and condensedmatter spectroscopy and other interactions of matter with particles and radiation.
1999 Volume 68 Issue 4 Pages
1392-1397
Published: April 01, 1999
Released on J-STAGE: October 01, 1999
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An intuitive discussion on features of L
2, 3 X-ray emission spectra in Fe, Co and Ni and magnetic circular dichroism (MCD), following theexcitation with circularly polarized X-ray, is given from a theoreticalside. A weak MCD at off-resonance excitation and a strong MCD at2p
3/2 and 2p
1/2 on-resonances, including their signs, areexplained in terms of the magnetic and spin quantum number dependence ofthe dipole transition and the symmetry of occupied 3d states. Thespectral weight transfer in the XES spectrum from the higher emissionenergy to the lower one and the difference in the extent of transferbetween the isotropic and dichroic spectra is explained by the helicitydependent Coster-Kronig decay, which does not manifest explicitly in MCDintensity for X-ray absorption.
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Taichi Okuda, Masato Kotsugi, Kan Nakatsuji, Masao Fujikawa, Shigemasa ...
Subject area: Optical properties and condensedmatter spectroscopy and other interactions of matter with particles and radiation.
1999 Volume 68 Issue 4 Pages
1398-1403
Published: April 01, 1999
Released on J-STAGE: October 01, 1999
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The Fermi surface of the noncuprate superconductor Sr
2RuO
4 has been studied in detail by two-dimensional angle resolved photoelectron spectroscopy (2D-ARPES) using a display-type electron spectrometer and a linearly polarized synchrotron radiation.The existence of the large Fermi surfaces agrees with previous band calculations and conventional ARPES measurements.From the comparison of the observed photoelectron intensity distribution of the Fermi surface with that of the simulation for atomic orbitals, the symmetry of the atomic orbitals composing the Fermi surfaces is revealed to be the dε;d
xy, d
yz, d
zx-like in contrast to the d
x2-y2-like orbital in the cuprate high-T
c super conductor.The possibility of the existence of the extended van-Hove singularity just below the Fermi level, which was suggested by recent conventional ARPES measurements, is also discussed.
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