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Volume 72, Issue 4
Displaying 1-38 of 38 articles from this issue
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Shoji Yamamoto, Hiromitsu Hori2003 Volume 72 Issue 4 Pages 769-772
Published: April 15, 2003
Released on J-STAGE: July 25, 2007
JOURNAL RESTRICTED ACCESSModifying the conventional antiferromagnetic spin–wave theory which is plagued by the difficulty of the zero-field sublattice magnetizations diverging in one dimension, we describe magnetic properties of Haldane-gap antiferromagnets. The modified spin waves, constituting a grand canonical bosonic ensemble so as to recover the sublattice symmetry, not only depict well the ground-state correlations but also give useful information on the finite-temperature properties.View full abstractDownload PDF (155K) -
Kyungwon An, Hee-Jong Moon2003 Volume 72 Issue 4 Pages 773-776
Published: April 15, 2003
Released on J-STAGE: July 25, 2007
JOURNAL RESTRICTED ACCESSWe report laser oscillations in whispering-gallery modes (WGMs) of a microsphere with its cavity quality factor Q unchanged for varied optical pumping intensities well above the laser threshold. Laser gain was present only in the evanescent-wave region of the lasing WGM around the microsphere equator, and thus pumping-induced Q degradation could be minimized, resulting in Q values maintained at 8(2)×109 regardless of the pumping strength.View full abstractDownload PDF (95K) -
Takeo Fujiwara, Susumu Yamamoto, Yasushi Ishii2003 Volume 72 Issue 4 Pages 777-780
Published: April 15, 2003
Released on J-STAGE: July 25, 2007
JOURNAL RESTRICTED ACCESSThe iterative perturbation theory of the dynamical mean field theory is generalized to arbitrary electron occupation for multi-orbital Hubbard bands. We present numerical results for doubly degenerate Eg bands on a simple cubic lattice. The spectrum shows the electron ionization and affinity levels of different electron occupations. For sufficiently large Coulomb interaction, a gap opens in the spectrum at an integer filling of electrons and the system becomes an insulator. The present scheme is easily combined with electronic structure theory in the local spin density approximation.View full abstractDownload PDF (121K) -
Yuji Muraoka, Zenji Hiroi2003 Volume 72 Issue 4 Pages 781-784
Published: April 15, 2003
Released on J-STAGE: July 25, 2007
JOURNAL RESTRICTED ACCESSAn efficient and clean method of doping transition metal oxides (TMOs) with hole carriers is presented. We have fabricated oxide heterostructures made of various TMO thin films grown on n-type titanium oxide substrates, and measured in-plane resistance under ultraviolet light irradiation. It is shown that the resistance of the insulating TMOs is reduced significantly with increasing light irradiance, as a result of photoinduced hole carrier injection from the titanium oxide substrates. A generic band structure for the heterojunctions is proposed, in which a large potential slope and a small barrier exist near the interface for photoinduced holes and electrons in the titanium oxides, respectively. This photocarrier injection (PCI) technique would provide us with a useful method to achieve the external control of hole carrier density in TMOs.View full abstractDownload PDF (172K) -
Takashi Kiyama, Yusuke Wakabayashi, Hironori Nakao, Hiroyuki Ohsumi, Y ...2003 Volume 72 Issue 4 Pages 785-788
Published: April 15, 2003
Released on J-STAGE: July 25, 2007
JOURNAL RESTRICTED ACCESSWe report the results of resonant X-ray scattering (RXS) measurement of superlattices which consist of La0.45Sr0.55MnO3 and La0.60Sr0.40MnO3 multilayers. An interference technique made it possible to observe RXS reflections from ferro-type orbital ordering in the superlattices. RXS can reveal the local circumstances around specific atoms in materials regulated atomically. In this experiment, we observed that the superlattice is actually composed of two kinds of layers with different lattice distortion states, presenting “orbital superlattices”, in which layers with different orbital states are stacked alternately in an atomic scale.View full abstractDownload PDF (316K) -
Tota Nakamura2003 Volume 72 Issue 4 Pages 789-792
Published: April 15, 2003
Released on J-STAGE: July 25, 2007
JOURNAL RESTRICTED ACCESSA possibility of the uniform antiferromagnetic order is pointed out in an S=1⁄2 ferromagnetic–antiferromagnetic (F–AF) random alternating Heisenberg quantum spin chain compound: (CH3)2CHNH3Cu(Clx Br1−x)3. The system exhibits bond alternation of strong random bonds that take ±2J and weak uniform AF bonds of −J. In pure concentration limits, the model reduces to the AF–AF alternation chain at x=0 and to the F–AF alternation chain at x=1. By using the nonequilibrium relaxation method of quantum Monte Carlo simulations, it is found that the uniform AF order exhibits critical behaviors in the intermediate concentration region. This explains the experimental observation of the magnetic phase transition. The present results suggest that the uniform AF order survives even in the presence of randomly located ferromagnetic bonds.View full abstractDownload PDF (145K) -
Kenji Shimizu, Matias Velázquez, Jean-Pierre Renard, Alexandre ...2003 Volume 72 Issue 4 Pages 793-796
Published: April 15, 2003
Released on J-STAGE: July 25, 2007
JOURNAL RESTRICTED ACCESSA single crystal of perovskite bilayer manganite La1.2Sr1.8Mn2O7 has been studied by the 55Mn NMR technique. The observed spectra at 4.2 K in zero external magnetic field are broad and spread in the frequency range 310–480 MHz. The shape of the spectrum depends strongly on the rf radiation field for exciting and refocusing a spin–echo signal. In external magnetic fields up to 1.75 T, signals arising from both metallic and insulating phases are observed, which is an evidence of the electronic phase separation.View full abstractDownload PDF (240K) -
Kozo Okada, Akio Kotani2003 Volume 72 Issue 4 Pages 797-800
Published: April 15, 2003
Released on J-STAGE: July 25, 2007
JOURNAL RESTRICTED ACCESSThe many-body nature of O 1s resonant X-ray emission spectroscopy (RXES) in edge-share-type quasi-one-dimensional cuprates with hole doping is discussed on the basis of finite-size cluster model calculations. In the case of hole-doped systems, the line shape of O 1s RXES strongly depends on the incident X-ray energy (ωin). This is just a manifestation of state-selectivity of RXES. When ωin is tuned at the upper Hubbard band, we observe inelastic scattering peaks due to the Zhang–Rice singlet (ZRS) and dd excitations besides the O 2p main band emission. On the other hand, when ωin is tuned at the ZRS band, the charge-transfer excitation edge region and the dd excitation peaks are significantly enhanced in accordance with the recent experiment for Ca2+xY2−xCu5O10.View full abstractDownload PDF (140K) -
Yuo-Hsien Shiau, Yih-Ferng Peng, Yi-Chen Cheng, Chin-Kun Hu2003 Volume 72 Issue 4 Pages 801-804
Published: April 15, 2003
Released on J-STAGE: July 25, 2007
JOURNAL RESTRICTED ACCESSWe propose a tunable microwave device consisting of a Gunn diode with time–delay feedback, which will emit chaotic microwaves. The wavelength is controlled by two incident laser beams which trigger moving multiple Gunn domains. Predicted phenomena include the coexistence of stationary and chaotic states, complicated hysteresis loops, and persistent bistabiliy. This device is potentially useful for applications such as secure microwave communications, memory devices and those involving photorefractive effects.View full abstractDownload PDF (106K) -
Masato Inoue, Hyeyoung Park, Masato Okada2003 Volume 72 Issue 4 Pages 805-810
Published: April 15, 2003
Released on J-STAGE: July 25, 2007
JOURNAL RESTRICTED ACCESSThe permutation symmetry of the hidden units in multilayer perceptrons causes the saddle structure and plateaus of the learning dynamics in gradient learning methods. The correlation of the weight vectors of hidden units in a teacher network is thought to affect this saddle structure, resulting in a prolonged learning time, but this mechanism is still unclear. In this paper, we discuss it with regard to soft committee machines and on-line learning using statistical mechanics. Conventional gradient descent needs more time to break the symmetry as the correlation of the teacher weight vectors rises. On the other hand, no plateaus occur with natural gradient descent regardless of the correlation for the limit of a low learning rate. Analytical results support these dynamics around the saddle point.View full abstractDownload PDF (270K) -
Kyungwon An2003 Volume 72 Issue 4 Pages 811-816
Published: April 15, 2003
Released on J-STAGE: July 25, 2007
JOURNAL RESTRICTED ACCESSA criterion for the validity of the single-atom approximation in the many-atom microlaser was proposed and its adequateness has been tested in semiclassical, quantum mechanical and quantum trajectory simulations. Through these studies we conclude that the single-atom approximation, employing the same emission probability formula for individual atoms as that of the single-atom micromaser theory is valid as long as the product of the atom-field coupling constant and the atom-field interaction time is much smaller than the square root of the mean cavity photon number.View full abstractDownload PDF (211K) -
Yousuke Watanabe, Kohki Takahashi, Satoshi Awaji, Kazuo Watanabe, Hiro ...2003 Volume 72 Issue 4 Pages 817-821
Published: April 15, 2003
Released on J-STAGE: July 25, 2007
JOURNAL RESTRICTED ACCESSX-ray diffraction measurements under high and low temperature, and magnetic field have been performed for the doped La1−xCaxMnO3+δ polycrystals to clarify the coexistent phases and their structures around the composition of x∼0.5. By measurements at high temperature, the transition from a Pnma to an Imma space group symmetry phase has been firstly observed in this system at the temperature between 500°C and 600°C. At low temperature, the importance of the measurement of (131) reflection is noticed and the phase fraction of two similar Pnma phases with ferromagnetic and anti-ferromagnetic states is determined. It is found that the application of the magnetic field by 5 T and the slight change of the composition x by 0.02 remarkably affect this phase fraction.View full abstractDownload PDF (241K) -
Akiko Harada, Fuyuki Shimojo, Kozo Hoshino2003 Volume 72 Issue 4 Pages 822-828
Published: April 15, 2003
Released on J-STAGE: July 25, 2007
JOURNAL RESTRICTED ACCESSThe dynamic properties of the liquid and the amorphous carbon are studied by empirical-potential molecular-dynamics (MD) simulations as well as ab initio MD methods based on the density-functional theory. As the empirical potential, the environment-dependent interatomic potential (EDIP) proposed recently by Marks is used. Detailed investigations on the density–density time correlation function, known as van Hove correlation functions, are given. It is shown that the EDIP is extremely transferable in the sense that the dynamic properties, as well as the static properties, of the disordered phases of carbon are well reproduced using the EDIP. It is also shown that the EDIP is usable for the hybrid ab initio/empirical-potential MD simulation, by applying the hybrid method to a graphite sheet (graphen) for investigating the dynamic properties such as the heat transfer.View full abstractDownload PDF (773K) -
Naurang L. Saini, Hiroyuki Oyanagi, Valerio Scagnoli, Toshimitsu Ito, ...2003 Volume 72 Issue 4 Pages 829-834
Published: April 15, 2003
Released on J-STAGE: July 25, 2007
JOURNAL RESTRICTED ACCESSWe have studied temperature dependent local structure of superconducting La2−xSrxCuO4 (0.105, 0.13, 0.20) single crystals by Cu K-edge extended x-ray absorption fine structure (EXAFS) measurements with polarization parallel to the in-plane Cu–O bonds. We find that, while underdoped crystals (x=0.105, 0.13) show anomalous temperature dependence, similar to the case of optimally doped system (x=0.15), overdoped crystal (x=0.20) does not reveal such anomaly. Correlated Debye–Waller factor (DWF) of the Cu–O bonds (distance broadening) has been used as an order parameter to determine characteristic local displacements in the CuO2 plane. The amplitude of temperature dependent step-like increase in the DWF at low temperature decreases with increasing doping. It has been discussed that decreasing electron–lattice interaction with increasing doping, shown by angle resolved photoemission measurements, is closely related to the evolving anomalous local CuO2 distortion and charge inhomogeneity with doping in the CuO2 plane of high Tc oxides.View full abstractDownload PDF (197K) -
Kensuke Doi, Yuhei Natsume2003 Volume 72 Issue 4 Pages 835-839
Published: April 15, 2003
Released on J-STAGE: July 25, 2007
JOURNAL RESTRICTED ACCESSCharacteristic features of fluctuations of Bose–Einstein condensations for systems of two-components in gas phases of alkali-metal atoms trapped by spherical harmonic potentials are discussed on the basis of numerical calculations. We concentrate our attention on the phases in which the spherical state ψ1 without vortex is surrounded by ψ2 with a vortex for the unit circulation q=1. These states are expressed by Gross–Pitaevskii equation, where a vortex-core is along the z-axis. We investigate properties of collective excitations by the linear analysis for bosonic excitations described as Bogoliubov equations. The behavior of each mode is discussed in relation with the role of interspecies repulsion in addition to that of intraspecies one. We point out the role of the new compressive mode which has two nodes on z-axis, in addition to that of the core mode without a node which have been previously discussed in the single-component system. Furthermore, we would like to emphasize that sliding modes show the branching features into in- and out-of-phase motions with increasing interspecies interaction. The dependence of those branchings on interspecies repulsion is explained by spatial shapes of relevant modes.View full abstractDownload PDF (368K) -
Chisa Hotta2003 Volume 72 Issue 4 Pages 840-853
Published: April 15, 2003
Released on J-STAGE: July 25, 2007
JOURNAL RESTRICTED ACCESSThis paper presents a unified theoretical picture of quasi-two-dimensional organic conductors in a new minimal model based on an anisotropic triangular lattice. These materials exhibit abundance of low-temperature physics, where the systematic understanding was lagging behind respective studies. This is ascribed to a variety in the electronic structure stemming from different arrangements of molecules, i.e. polytypes. We provide a way of mapping different polytypes into our minimal model, where a choice of four different band parameters enables the simple relationships among them. The generalized ground state phase diagram of this model on the plane of these band parameters is obtained from the mean-field calculations with on-site and inter-site Coulomb interactions. By associating the actual materials with the results of calculations, their ground state differences are systematically understood.View full abstractDownload PDF (1450K) -
Takahiro Maehira, Takashi Hotta, Kazuo Ueda, Akira Hasegawa2003 Volume 72 Issue 4 Pages 854-864
Published: April 15, 2003
Released on J-STAGE: July 25, 2007
JOURNAL RESTRICTED ACCESSIn order to investigate electronic properties of recently discovered heavy fermion superconductors CeTIn5 (T = Ir and Co), we employ the relativistic linear augmented-plane-wave (RLAPW) method to clarify the energy band structures and Fermi surfaces of those materials. The obtained energy bands mainly due to the large hybridization between Ce 4f and In 5p states well reproduce the Fermi surfaces consistent with the de Haas-van Alphen experimental results. However, when we attempt to understand magnetism and superconductivity in CeTIn5 from the microscopic viewpoint, the energy bands obtained in the RLAPW method are too complicated to analyze the system by further including electron correlations. Thus, it is necessary to prepare a more simplified model, keeping correctly the essential characters of the energy bands obtained in the band-structure calculation. For the purpose, we construct a tight-binding model for CeTIn5 by including f–f and p–p hoppings as well as f–p hybridization, which are expressed by the Slater–Koster integrals, determined by the direct comparison with the band-calculation result. Similarity and difference between CeIrIn5 and CeCoIn5 are discussed based on the obtained tight-binding model, suggesting a significant importance of the effect of crystalline electric field to understand the difference in electronic properties among CeTIn5.View full abstractDownload PDF (937K) -
Yukio Yasui, Satoshi Iikubo, Hiroshi Harashina, Taketomo Kageyama, Mas ...2003 Volume 72 Issue 4 Pages 865-872
Published: April 15, 2003
Released on J-STAGE: July 25, 2007
JOURNAL RESTRICTED ACCESSNeutron diffraction studies have been carried out in the applied magnetic field H(||[0\\bar11]) on a single crystal of pyrochlore ferromagnet Nd2Mo2O7, whose Hall resistivity (ρH) has been reported to have quite unusual magnetic field (H)- and temperature (T)-dependences. The intensities of the observed magnetic reflections have been reproduced at 1.6 K as a function of H, by considering the change of the magnetic structure with H, where effects of the exchange fields at the Mo and Nd sites induced by the Mo–Mo and Mo–Nd exchange interactions and the single ion anisotropies of Mo- and Nd-moments are considered. From the H-dependent magnetic structure, the H-dependence of ρH has been calculated by using the chiral order mechanism. By comparing the result with the H-dependence of the observed ρH, it is found that the chiral order mechanism does not work well in the present system.View full abstractDownload PDF (315K) -
Hiroyasu Masuda, Toshiaki Fujita, Takeshi Miyashita, Minoru Soda, Yuki ...2003 Volume 72 Issue 4 Pages 873-878
Published: April 15, 2003
Released on J-STAGE: July 25, 2007
JOURNAL RESTRICTED ACCESSTransport and magnetic measurements have been carried out on perovskite Co-oxides R1−xAxCoO3 (R = La, Pr, and Nd; A = Ba, Sr and Ca; 0≤x≤0.5: All sets of the R and A species except Nd1−xBaxCoO3 have been studied.). With increasing the Sr- or Ba-concentration x, the system becomes metallic ferromagnet with rather large magnetic moments. For R = Pr and Nd and A = Ca, the system approaches the metal–insulator phase boundary but does not become metallic. The magnetic moments of the Ca-doped systems measured with the magnetic field H=0.1 T are much smaller than those of the Ba- and Sr-doped systems. The thermoelectric powers of the Ba- and Sr-doped systems decrease from large positive values of lightly doped samples to negative ones with increasing doping level, while those of Ca-doped systems remain positive. These results can be understood by considering the relationship between the average ionic radius of R1−xAx and the energy difference between the low spin and intermediate spin states. We have found the resistivity-anomaly in the measurements of Pr1−xCaxCoO3 under pressure in the wide region of x, which indicates the existence of a phase transition different from the one reported in the very restricted region of x∼0.5 at ambient pressure [Tsubouchi et al. Phys. Rev. B 66 (2002) 052418.]. No indication of this kind of transition has been observed in other species of R.View full abstractDownload PDF (1492K) -
Akinori Tanaka, Kazutoshi Takahashi, Hiroyuki Sasaki, Wakako Gondo, Sh ...2003 Volume 72 Issue 4 Pages 879-883
Published: April 15, 2003
Released on J-STAGE: July 25, 2007
JOURNAL RESTRICTED ACCESSWe have carried out an angle-resolved photoemission study of double Ag nanofilm structures, composed of an outer Ag nanofilm/Cu barrier layer/inner Ag nanofilm/Cu(111) substrate, in order to investigate the electronic coupling between the quantum-well (QW) states. It is found that the eigenvalues of coupled QW states in the present double Ag nanofilm structures show the avoided-crossing behavior, indicative of the electronic coupling between the QW states through a thin Cu barrier layer. Furthermore, it is found that electronic coupling strength decreases with increasing the Cu barrier layer and inner Ag nanofilm thickness. We have compared these experimental results with the theoretical calculations based on the nearly-free-electron approximation. From these results, we discuss the electronic coupling between the QW states in the double Ag nanofilm structures with various configurations.View full abstractDownload PDF (136K) -
Hirono Fukazawa, Hiroaki Ikeda, Kosaku Yamada2003 Volume 72 Issue 4 Pages 884-894
Published: April 15, 2003
Released on J-STAGE: July 25, 2007
JOURNAL RESTRICTED ACCESSWe evaluate the dominant superconducting pairing symmetry in 3-dimensional cubic lattice structures within the third-order perturbation theory with respect to the on-site coulomb repulsion. We show that the third-order vertex correction term, which has a critical contribution to the p-wave state in the 2-dimensional systems, is also important in the 3-dimensional system. In the three dimensional systems, we obtain the superconsucting transition temperature Tc about one-order lower than that in 2-dimensional systems. This result suggests that magnetic ground states are dominant in the usual 3-dimensional system in accordance with the experimental observation. However there exist heavy fermion systems where the magnetic order is suppressed by the Kondo effect. Thus, our theory can be applied to the heavy fermion system and well explain the superconductivity in the system.View full abstractDownload PDF (423K) -
Nobukatsu Yoshida, Yasuhiro Asano, Hiroyoshi Itoh, Yukio Tanaka, Jun-i ...2003 Volume 72 Issue 4 Pages 895-899
Published: April 15, 2003
Released on J-STAGE: July 25, 2007
JOURNAL RESTRICTED ACCESSEffects of impurity-scattering on a zero-bias conductance peak in ferromagnet/insulator/d-wave superconductor junctions are theoretically studied. The impurities are introduced through the random potential in ferromagnets near the junction interface. As in the case of normal-metal/insulator/d-wave superconductor junctions, the magnitude of zero-bias conductance peak decreases with increasing the degree of disorder. However, when the magnitude of the exchange potential in ferromagnet is sufficiently large, the random potential can enhance the zero-bias conductance peak in ferromagnetic junctions.View full abstractDownload PDF (167K) -
Satoru Kobayashi, Fumitake Itoh2003 Volume 72 Issue 4 Pages 900-903
Published: April 15, 2003
Released on J-STAGE: July 25, 2007
JOURNAL RESTRICTED ACCESSWe have investigated the influence of the ferromagnet magnetization on the transport critical-current density Jc in ferromagnet (Co)/superconductor (Nb)/ferromagnet (Co) trilayers under applied fields parallel to the film surface. Irrespective of field polarity, the pronounced peak of Jc was observed below the lower critical field Hc1, in contrast to usual monotonic decrease of Jc with field. We find that the position of the minimum in Jc appearing around zero field, is dependent on the sweep direction of the applied field. These results can be explained by the pair-breaking effect that is controlled by the relative alignment between the applied field and the in-plane magnetization of the Co layer.View full abstractDownload PDF (112K) -
Taijiro Arimoto, Takashi Ohara, Atsushi Tsuruta, Akito Kobayashi, Yosh ...2003 Volume 72 Issue 4 Pages 904-910
Published: April 15, 2003
Released on J-STAGE: July 25, 2007
JOURNAL RESTRICTED ACCESSWe investigate a transition between the superconducting phase and the Mott insulator phase in the d–p model by using the slave-boson method and the 1⁄N-expansion theory, where the pairing interaction is given by the superexchange interaction Js. We show that the competition between the pairing interaction and the Fermi energy induces the transition at finite doping rate.View full abstractDownload PDF (292K) -
Kazuo Hida2003 Volume 72 Issue 4 Pages 911-915
Published: April 15, 2003
Released on J-STAGE: July 25, 2007
JOURNAL RESTRICTED ACCESSThe S=1⁄2 frustrated Heisenberg chains with bond alternation is known to exhibit a magnetization plateau at half of the saturation magnetization Ms accompanied by the spontanuous translational symmetry breakdown. The effect of randomness on the magnetization process of this model is investigated. First we consider the mixture of the two kinds of chains both of which possess the Ms⁄2-plateau in the common interval of the magnetization field. The plateau at Ms⁄2 is found to vanish immediately if the randomness is switched on in agreement with Totsuka’s prediction. The small plateau also appears near the saturation field due to the localization of inverted spins around the minority bond. On the other hand, if the stronger bond is replaced by the ferromagnetic bonds randomly, the randomness induced fractional plateau appears as in the nonfrustrated case. The plateau at Ms⁄2 does not simply vanish but shifts and splits into two smaller plateaux. The magnetization on this plateau varies nonlinearly with 1−p. The physical origin of this behavior is explained based on the strong coupling picture.View full abstractDownload PDF (203K) -
Peijie Sun, Yosikazu Isikawa, Qingfeng Lu, Dexuan Huo, Tomohiko Kuwai2003 Volume 72 Issue 4 Pages 916-921
Published: April 15, 2003
Released on J-STAGE: July 25, 2007
JOURNAL RESTRICTED ACCESSThe electrical resistivity, magnetic susceptibility and specific heat measurements were performed on Ce(Pd1−xCux)2Al3 (x=0.0–0.7) system to investigate the effects induced by Cu substitution in the heavy fermion compound CePd2Al3. A dramatic evolution of the magnetic properties was observed with the substitution of Pd by Cu: (1) a small amount of Cu (x<0.1) in CePd2Al3 leads to a rapid decrease of the antiferromagnetic transition temperature TN; (2) passing through a crossover region without a long-range magnetic order, a ferromagnetic-like state, which reveals an enhanced magnetic susceptibility and a distinct peak in the specific heat curve at low temperatures, occurs around x=0.1–0.4; (3) by furthering the substitution through a second crossover region, however, the antiferromagnetic ordering is recovered close to x=0.5–0.7. A decrease tendency of the Kondo temperature TK with increasing x is derived from the analysis on the specific heat results. It is suggested that the change of the conduction-electron concentration rather than the chemical pressure dominates the evolution of the physical properties in this system.View full abstractDownload PDF (796K) -
Sheng Xu, Yutaka Moritomo, Akihiko Machida, Kenji Ohoyama, Arao Nakamu ...2003 Volume 72 Issue 4 Pages 922-929
Published: April 15, 2003
Released on J-STAGE: July 25, 2007
JOURNAL RESTRICTED ACCESSWe have derived the magnetic phase diagram for Nd1⁄2Ca1⁄2(Mn1−yMy)O3 (M = Ru, Cr and Sc) based on the neutron powder diffraction measurements. We found that the Ru- and Cr-doping induces an antiferromagnetic-to-ferromagnetic transition at y=0.01–0.02, while the Sc-doping does not induce the transition up to y=0.10. We have found significant dopant dependent effects on the distortion of the MnO6 octahedra in the heavily-doped region of the long-c phase: the MnO6 shape approached to the 2-long/4-short type with Ru-doping, while it does to the 4-long/2-short type with Sc-doping. Absence of the ferromagnetic phase in the Sc-doped system can be ascribed to (1) a strong charge-ordering instability due to the 4-long/2-short type distortion of the MnO6 octahedra and (2) the reduced effective one-electron bandwidth due to the Sc3+ (d0) impurities.View full abstractDownload PDF (251K) -
Kiyoichiro Motoya, Keiko Hioki2003 Volume 72 Issue 4 Pages 930-937
Published: April 15, 2003
Released on J-STAGE: July 25, 2007
JOURNAL RESTRICTED ACCESSNeutron scattering study on a pseudo-binary alloy system Fe65(Ni1−xMnx)35 has been made to clarify the microscopic magnetic state in a system of competing magnetic interactions. Magnetic diffuse scattering patterns arising from short-range ferromagnetic and antiferromagnetic correlations have been observed in wide concentration and temperature ranges. The result shows that the magnetic phase diagram determined by macroscopic measurements does not properly represent the magnetic state of the competing magnetic interaction system.View full abstractDownload PDF (195K) -
Akihisa Koga, Norio Kawakami, Manfred Sigrist2003 Volume 72 Issue 4 Pages 938-942
Published: April 15, 2003
Released on J-STAGE: July 25, 2007
JOURNAL RESTRICTED ACCESSWe investigate quantum phase transitions of the two-dimensional S=1 Shastry–Sutherland model, which is characterized by the frustrated orthogonal-dimer structure, by means of the exact diagonalization method and the Ising-type series expansion method. We clarify how distinct spin gap phases realized in the chain system are adiabatically connected to those in the two-dimensional Shastry–Sutherland model. The effect of single-ion anisotropy is also discussed.View full abstractDownload PDF (139K) -
Masayuki Hagiwara, Yasuo Narumi, Kazuhiko Minami, Koichi Kindo, Hideak ...2003 Volume 72 Issue 4 Pages 943-946
Published: April 15, 2003
Released on J-STAGE: July 25, 2007
JOURNAL RESTRICTED ACCESSWe report the results of magnetic susceptibility (χ) and high field magnetization measurements on single crystal samples of a copper chain compound Cu(3-Clpy)2(N3)2 (3-Clpy = 3-chloropyridine, C5H4NCl) that is regarded as an S=1⁄2 tetramer chain with ferromagnetic–ferromagnetic–antiferrmagnetic–antiferromagnetic bond alternating interactions. As the temperature (T) is decreased, the χT exhibits a round minimum at about 10 K and a successive abrupt increase, which is typical of a quantum ferrimagnet. The magnetization curves up to 40 T in a pulsed magnetic field at 1.3 K shows a steep increase around zero field and a plateau up to 27 T followed by a steep increase before saturation. Since we observed large hystereses around zero field and saturation field in pulsed fields, we performed the magnetization measurements under static fields up to 35 T to get equilibrium magnetizations and compared them witn the calculated ones. The calculated magnetization at each magnetic site against magnetic fields indicates a spin reduction probably arising from the quantum many body effect except at the site which ferromagnetically couples to both neighboring sites.View full abstractDownload PDF (389K) -
Masaki Yokoyama, Masashi Kosaka, Nobuo Mori, Yoshiya Uwatoko, Hideki A ...2003 Volume 72 Issue 4 Pages 947-950
Published: April 15, 2003
Released on J-STAGE: July 25, 2007
JOURNAL RESTRICTED ACCESSThe magnetic properties of a single-crystalline sample Ce2Sc3Ge4 have been investigated, for the first time. On the basis of the magnetization, magnetic susceptibility, electrical resistivity and specific heat measurements, we suggest that Ce2Sc3Ge4 is an antiferromagnetic Kondo compound with TN=5.0 K. The saturated magnetic moment for the Ce atom is estimated to be 1.1μB at T=1.5 K by the magnetization measurements. Electronic specific heat coefficient γ is estimated to be 49.5 mJ/molK2, indicating that the system is described as a medium-heavy fermion compound.View full abstractDownload PDF (331K) -
Hideaki Kitahara, Tsuyoshi Kawaguchi, Junichi Miyashita, Mitsuo Wada T ...2003 Volume 72 Issue 4 Pages 951-955
Published: April 15, 2003
Released on J-STAGE: July 25, 2007
JOURNAL RESTRICTED ACCESSOne-dimensional photonic crystals were fabricated by using a periodic microstrip line with a lattice constant of 16.3 mm. Wide band gaps around 5 GHz were observed by a network analyzer. Microstrip lines with an impurity line that disturbed the periodicity were also fabricated and a sharp transmission peak, which is due to the impurity mode, was observed in the band gap region. The measured transmission and reflection spectra were in very good accordance with those calculated by the method of moments. The Q factor of the impurity modes was strongly dependent on the number of unit cells of the periodic lines adjacent to the impurity line and also on the value of the dielectric loss of the substrate material. The spatial distribution of the electric field of the transmitting modes and the impurity modes of the electromagnetic wave were simulated using the method of moments, and localization of the impurity modes was clearly evident.View full abstractDownload PDF (1039K) -
K. Tainaka, N. Yoshida, N. Terazawa, N. Nakagiri, T. Hashimoto, Y. Tak ...2003 Volume 72 Issue 4 Pages 956-961
Published: April 15, 2003
Released on J-STAGE: July 25, 2007
JOURNAL RESTRICTED ACCESSThe so-called Lotka–Volterra model, which is thought to be appropriate for the dynamics of mutualistic relationship, tells us that mutualism does not play positive roles for the stability of ecosystem. When the mutualistic interactions between species are stronger than a certain threshold, population sizes of species unlimitedly increases. In the present paper, in order to prevent the divergence, we apply a lattice model, and introduce extended Lotka–Volterra equations. The latter is the mean-field theory of the former. These models contain the property of competition due to space limitation. In both models population is usually stable, when the intensity of mutualism are strong. In the lattice model, spatial distribution of species naturally evolves into a specific pattern of either mutualism or competition, depending on environmental conditions.View full abstractDownload PDF (276K) -
Taro Ito, Noboru Shimomura, Tsutomu Yabuzaki2003 Volume 72 Issue 4 Pages 962-963
Published: April 15, 2003
Released on J-STAGE: July 25, 2007
JOURNAL RESTRICTED ACCESSDownload PDF (79K) -
Nirmal C. Sacheti, Pallath Chandran, Tayfour El-Bashir2003 Volume 72 Issue 4 Pages 964-965
Published: April 15, 2003
Released on J-STAGE: July 25, 2007
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Kazuo Gesi2003 Volume 72 Issue 4 Pages 966-967
Published: April 15, 2003
Released on J-STAGE: July 25, 2007
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Shuichiro Anzai, Hisanori Hanai, Satoshi Hashimoto, Yoshiyasu Takayama ...2003 Volume 72 Issue 4 Pages 968-969
Published: April 15, 2003
Released on J-STAGE: July 25, 2007
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Naoki Kobayashi, Takuya Sato, Yoshihiro Yamazaki, Mitsugu Matsushita2003 Volume 72 Issue 4 Pages 970-971
Published: April 15, 2003
Released on J-STAGE: July 25, 2007
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