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Volume 67, Issue 7
Displaying 51-67 of 67 articles from this issue
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Yukihiro Okuno, Kazumasa MiyakeSubject area: Magnetic properties and materials.
1998 Volume 67 Issue 7 Pages 2469-2476
Published: July 01, 1998
Released on J-STAGE: October 01, 1999
JOURNAL RESTRICTED ACCESSThe weak antiferromagnetism of URu2Si2 is discussed on thebasis of a duality model which takes into account salient features of bothitinerant fermions and “localized” component of spin degrees of freedom.The problem is analyzed in the framework of induced-moment mechanismby taking a singlet-singlet crystal field scheme together with the nestingproperty of partial Fermi surface of itinerant fermions . It is shown that theextremely small ordered moment m of O(10-2×μB) can becompatible with the large specific-heat jump at the transition temperatureTN. Analysis performed in the presence of external magnetic fieldshows that the field dependence of m in the limit T→ 0 and TNdo not scale except very near the critical field Bc whichis consistent with a recent observation by Mentink et al. It is alsoshown that the antiferromagnetic magnetic order gives rise to a tinyamount of antiferromagnetic orbital order of f-electrons.View full abstractDownload PDF (634K) -
Masako SaitoSubject area: Magnetic properties and materials.
1998 Volume 67 Issue 7 Pages 2477-2483
Published: July 01, 1998
Released on J-STAGE: October 01, 1999
JOURNAL RESTRICTED ACCESSOur former theory [H. Fukuyama et al.: J. Phys. Soc. Jpn. 65 (1996) 1182.] of the coexistence of two long range orderings of spin-Peierls (SP) lattice dimerization and antiferromagnetic staggered moments in disordered SP systems have been extended in the treatment of impurity effects. First it is shown that long range order of the lattice dimerization can be destroyed above a critical density of impurity in accordance with recent experimental results. Secondly effects of magnetic fields are investigated in terms of soliton formations. In weakly disordered systems magnetic discommensurations are found to be formed around each impurity even in relatively weak fields and the magnetization process is expected to show two steps.View full abstractDownload PDF (583K) -
Yoshikazu Tabata, Toshifumi Taniguchi, Masugu Sato, Shuzo Kawarazaki, ...Subject area: Magnetic properties and materials.
1998 Volume 67 Issue 7 Pages 2484-2487
Published: July 01, 1998
Released on J-STAGE: October 01, 1999
JOURNAL RESTRICTED ACCESSThe specific heats and the susceptibilities of Ce(Ru1-xRhx)2Si2 single crystals (x = 0, 0.03 and 0.05) were studied between 0.1 and 10 K. The magnetic ground state of Ce(Ru1-xRhx)2Si2 is found to be a Fermi liquid even near the critical concentration x =0.03. x = 0.05 compound takes place a spin density wave transition at around 2 K, which is an antiferromagnetic order of itinerant heavy electrons by nesting in the Fermi liquid state. The low temperature behavior of the specific heat and the susceptibility were well explained by the effect of spin fluctuations based on the SCR theory.View full abstractDownload PDF (331K) -
Masanori Hidaka, Takashi Eguchi, Isao YamadaSubject area: Magnetic properties and materials.
1998 Volume 67 Issue 7 Pages 2488-2494
Published: July 01, 1998
Released on J-STAGE: October 01, 1999
JOURNAL RESTRICTED ACCESSIn several experimental studies of electron paramagnetic resonance and antiferromagnetic resonance performed on the one-dimensional Heisenberg antiferromagnet KCuF3, a Dzyaloshinsky-Moriya (DM) antisymmetric exchange interaction between spins on the c-axis was confirmed. However, the crystal symmetry with the space group D4h18 - I4/mcm that had been accepted then did not allow this interaction. Thus we doubted the old crystal structure. Improving the quality of single-crystal samples, we reexamine the crystal structure of KCuF3 by using an X-ray diffraction technique at room temperature. As a result, we confirm that F-atoms on the c-axis are displaced from the Cu-Cu bonding lines, which differs from the old structure. Consequently, a new superlattice structure is formed both along the c-axis and in the c-plane. On the basis of the newly found structure, we determine that the space group is D24 - P212121, and find that the local symmetry around a Cu-Cu bonding line along the c-axis allows the DM interaction with the DM vector perpendicular to the c-axis.View full abstractDownload PDF (617K) -
Duhwa Eom, Masayasu Ishikawa, Jiro Kitagawa, Naoya TakedaSubject area: Magnetic properties and materials.
1998 Volume 67 Issue 7 Pages 2495-2500
Published: July 01, 1998
Released on J-STAGE: October 01, 1999
JOURNAL RESTRICTED ACCESSSeveral pseudoternary compounds of the CeCoGe3-xSix system were studied by magnetic-susceptibility, electrical-resistivity and specific-heat measurements. Substitution of silicon for germanium generates the normal chemical pressure and enhances the exchange interaction. The antiferromagnetism in CeCoGe3 is ultimately suppressed around x=1.2 by the enhanced Kondo effect. Non-Fermi liquid-like behavior has been observed around the critical concentration and an intermediate-valence regime with a very high Kondo temperature of the order of 900, K is followed farther on in the silicon rich region.View full abstractDownload PDF (505K) -
Seiichi Kato, Hideaki Kitazawa, Hiroyuki Suzuki, Giyuu KidoSubject area: Magnetic properties and materials.
1998 Volume 67 Issue 7 Pages 2501-2504
Published: July 01, 1998
Released on J-STAGE: October 01, 1999
JOURNAL RESTRICTED ACCESSMagnetization along three main symmetry axes of a PrNi5 single crystal has been measured in stationary magnetic fields up to 28 T at 1.5 K. The a- and b- are easy magnetization axes and a metamagnetic process is observed along the a-axis. Magnetization curves along easy magnetization axes, particularly the a-axis, are widely different from calculated results by using the Hamiltonian involving the crystalline electric field (CEF) effect, Zeeman coupling and exchange interaction. But taking account of the quadrupolar interaction in addition to them, we are able to improve the curves significantly.View full abstractDownload PDF (271K) -
Takeo Jo, Tatsuya ShishidouSubject area: Magnetic properties and materials.
1998 Volume 67 Issue 7 Pages 2505-2509
Published: July 01, 1998
Released on J-STAGE: October 01, 1999
JOURNAL RESTRICTED ACCESSThe relationship between the magnetic state of divalent Co and Fe ions in the octahedral crystal field and the isotropic L2, 3 X-ray absorption spectroscopy (XAS) spectrum is discussed with switching on and off the 3d spin-orbit interaction on the basis of an atomic multiplet calculation. The existence of orbital magnetic moment Morb of --1μB is shown to manifest especially in L2 region as a narrow spectrum compared with that for Morb = 0 for both ions.A deviation of L3:L2 braching ratio from the statistical ratio 2 is also shown to be closely related with the existence of Morb for both ions. In the light of our findings, the magnetic state of both ions in CoO and FeO is discussed. The role of isotropic core XAS as a means to determine Morb in systems with no net magnetization is stressed.View full abstractDownload PDF (388K) -
Atsushi Koyanagi, Yoshiyuki Yoshida, Yasushi Kimura, Rikio Settai, Kiy ...Subject area: Magnetic properties and materials.
1998 Volume 67 Issue 7 Pages 2510-2513
Published: July 01, 1998
Released on J-STAGE: October 01, 1999
JOURNAL RESTRICTED ACCESSWe measured the electrical resistvity, specific heat and de Haas-van Alphen (dHvA) oscillation of an antiferromagnetic compound GdCu2.The magnetic entropy, which was obtained from the specific heat, reaches Rln8 above 47 K, which is close to the Néel temperature of 40 K.The dHvA branches both in the antiferromagnetic state and the field-induced ferromagnetic state are highly different from those of a non-magnetic reference compound YCu2 or PrCu2. The Fermi surface in GdCu2 is most likely altered by the magnetic state.View full abstractDownload PDF (315K) -
Shojiro Kimura, Hitoshi Ohta, Mitsuhiro Motokawa, Tetsuya Yokoo, Jun A ...Subject area: Magnetics resonances and relaxations in condensed matter; MÖssbauer effect.
1998 Volume 67 Issue 7 Pages 2514-2521
Published: July 01, 1998
Released on J-STAGE: October 01, 1999
JOURNAL RESTRICTED ACCESSWe have performed submillimeter wave ESR measurement of Haldane system Y2BaNiO5 in the frequency region from 50 to 383, GHz using the pulsed magnetic field up to 16, T. Due to the excess oxygens, a few percent of Ni2+ ions of Y2BaNiO5, which we used, are substituted by the Ni3+ ion of which spin is S=1/2. The ESR signals coming from the S=1/2 degrees of freedom originated by the Ni3+ ion at the end of the finite chain, are observed at 4.2, K. The frequency-field relations of these ESR signals are analyzed by the model based on the VBS model, which is used in the case of Cu2+ doped NENP. The signs of the single ion anisotropies D and E are determined from the analysis.View full abstractDownload PDF (604K) -
Chien–Sheng Huang, Ming–Fa Lin, Der–San ChuuSubject area: Dielectric properties and materials.
1998 Volume 67 Issue 7 Pages 2522-2528
Published: July 01, 1998
Released on J-STAGE: October 01, 1999
JOURNAL RESTRICTED ACCESSElementary excitations in a cylinder bundle, which is formed by packing the same hollow tubules into a two-dimensional triangular lattice, are studied. The dielectric response function is calculated within the linear response approximation. The electronic excitations of the cylinder bundle are the superposition of those of all tubules. Due to the intertube Coulomb interactions, their characteristics quite differ from those of an isolated tubule. The plasmon, which corresponds to the coherent oscillations of all carriers, could exhibit a prominent peak in excitation spectrum. The excitation properties strongly depend on the tubular radius, the effective electron mass, and the magnitude and the direction of the momentum transfer (q). At small momentum, there exists a simple relation between excitation properties and polar angles (θ 's). Both intensity of excitation spectrum and plasmon frequency decrease as θ increases. The collective plasma oscillations parallel and perpendicular to the tubular axis contrast sharply with each other, which clearly illustrates the anisotropic behavior. The ratio between these two plasmon frequencies is found to be smaller than √2.View full abstractDownload PDF (547K) -
Masayuki Udagawa, Hiroaki Hata, Shigeki Nimori, Tsutomu Minami, Norio ...Subject area: Optical properties and condensedmatter spectroscopy and other interactions of matter with particles and radiation.
1998 Volume 67 Issue 7 Pages 2529-2533
Published: July 01, 1998
Released on J-STAGE: October 01, 1999
JOURNAL RESTRICTED ACCESSLa (P_1) and apical oxygen (P2) vibrations along the c-axis, which are A1g-symmetry in the tetragonal phase (I4/mmm), have been systematically investigated for K2NiF4-type oxide superconductors; La2CuO4+δ (δ=0, 0.014, 0.063), La1.85Sr0.15CuO4, and Sr2RuO4. For La2CuO4+δ, with increasing of the excess oxygen concentration (δ), the intensity of P2 decreases exponentially as a function of δ at room temperature.This decrease can be understood by the shielding effect due to the doped carriers along the c-axis.With decreasing temperature, the intensity of P2 increases for La2CuO4.063 and La1.85Sr0.15CuO4 at low temperature, while La2CuO4 and Sr2RuO4 do not show such anomaly. This might be explained by the decrease of the shielding effect due to the charge confinement along the c-axis.The appearance of the excess oxygen vibration along the c-axis shows that the transition at about 250 K is due to the freezing of the itineracy of the excess oxygen for La2CuO4.063.View full abstractDownload PDF (405K) -
Kazuro Shimokawa, Yoshiro Hanyu, Gen MatsumotoSubject area: Biophysics.
1998 Volume 67 Issue 7 Pages 2534-2537
Published: July 01, 1998
Released on J-STAGE: October 01, 1999
JOURNAL RESTRICTED ACCESSThis paper describes detailed bifurcation characteristics of firing (time sequence of action potentials) observed in squid giant axons as a function of temperature.The firing is spontaneously induced when the axon is immersed in Ca-reduced ASW (Artificial seawater) without any electrical stimulation.The firing observed above a critical temperature (high-temperature phase firing) is periodic, while the one below the critical temperature (low-temperature) is aperiodic.Our present analysis on the firing shows that aperiodic firing is chaotic, and bifurcation from periodic oscillation to chaos occurs through the type-III intermittency.The type-III bifurcation to chaos should take place through some temperature-dependent properties of the axonal membrane in itself.One of the most probable candidates underlying chaos and bifurcation mechanisms in this experiment could be temperature-dependednt spatial interaction along the longitudinal direction of the squid giant axon.View full abstractDownload PDF (308K) -
Ken–ichi OshioSubject area: Other areas of research of general interest to physicists.
1998 Volume 67 Issue 7 Pages 2538-2545
Published: July 01, 1998
Released on J-STAGE: October 01, 1999
JOURNAL RESTRICTED ACCESSThis paper describes a simulational study on bifurcation and chaos of current oscillations in semiconductor with NDC (\underline{N}egative \underline{D}ifferential \underline{C}onductivity) induced by the recombination instability.A one-dimensional model of gold-doped n-Ge has been proposedin which the recombination instability leads the system to instability and current oscillations, and the computations have been performed under the boundary conditions with d.c. bias.We found that this system exhibits complicated structure of bifurcations for current oscillations including chaotic behavior and unusual truncated branches on bifurcation diagrams at the transition region between two basic oscillation modes in the parameter space.View full abstractDownload PDF (701K) -
Tomoyuki Nagaya, Yasuhiro Hikita, Hiroshi Orihara, Yoshihiro IshibashiSubject area: Other areas of research of general interest to physicists.
1998 Volume 67 Issue 7 Pages 2546-2550
Published: July 01, 1998
Released on J-STAGE: October 01, 1999
JOURNAL RESTRICTED ACCESSThe growth of the cholesteric finger pattern under an electric field and a magnetic field was investigated experimentally.A phase diagram of the appearing patterns was constructed by changing the magnetic field H and the electric voltage V.There were six regions, numbered as I, II, III, IV, IV′ and V, in the H-V phase diagram, where the growth of finger pattern was observed in the regions III and IV. It was found that in the region III the cholesteric finger grew up toward the direction of magnetic field and in the region IV the dendritic finger became elliptic due to the anisotropy of growth velocity as the increase of H. The growth velocity of the finger was enhanced by the magnetic field especially for the direction parallel to the magnetic field. The preferred direction of the finger growth was discussed by considering the interaction energy between the director and the magnetic field.View full abstractDownload PDF (686K) -
Yoshiyuki Yoshida, Atsushi Mukai, Rikio Settai, Yoshichika Onuki, Humi ...Subject area: Electronic transport in condensed matter.
1998 Volume 67 Issue 7 Pages 2551-2552
Published: July 01, 1998
Released on J-STAGE: October 01, 1999
JOURNAL RESTRICTED ACCESSDownload PDF (160K) -
Kiyohiro Sugiyama, Miho Nakashima, Atsushi Koyanagi, Shingo Araki, Koi ...Subject area: Magnetic properties and materials.
1998 Volume 67 Issue 7 Pages 2553-2554
Published: July 01, 1998
Released on J-STAGE: October 01, 1999
JOURNAL RESTRICTED ACCESSDownload PDF (184K) -
Fuminao Shimizu, Masaaki TakashigeSubject area: Dielectric properties and materials.
1998 Volume 67 Issue 7 Pages 2555-2556
Published: July 01, 1998
Released on J-STAGE: October 01, 1999
JOURNAL RESTRICTED ACCESSDownload PDF (210K)