巻号一覧
76 巻, 12 号
選択された号の論文の38件中1～38を表示しています
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Yuki Oshiro, Osamu Sano2007 年 76 巻 12 号 p. 123401
発行日: 2007/12/15
公開日: 2010/08/12
ジャーナル 認証ありAn experimental study is made on the pattern formation of a sand bed immersed in a viscous fluid between two concentric cylinders of finite depth; the channel width is sufficiently large as compared with the particle size. The upper boundary of the fluid is in contact with an annular ring made of transparent acrylic resin, which slides at a constant angular velocity, whereas other boundaries are at rest. New results on the onset and growth of sand ripples, the propagation and interaction of the ripples, and the long-term behavior for adjusting to a constant wavelength are presented.抄録全体を表示PDF形式でダウンロード (367K) -
Sadao Masamune, Akio Sanpei, Ryuya Ikezoe, Takumi Onchi, Ken-Ichi Mura ...2007 年 76 巻 12 号 p. 123501
発行日: 2007/12/15
公開日: 2010/08/12
ジャーナル 認証ありA reversed field pinch (RFP) machine with aspect ratio of as low as 2 (R⁄a=0.51 m/0.25 m) has been constructed for the experimental study of new RFP regime. Low-aspect ratio RFP plasmas have been produced in a resistive wall vacuum vessel for the first time. Initial results on discharge characteristics of the low-A RFP plasmas are presented. This experiment serves our study on new RFP regime with expected characteristics of simpler MHD dynamic arising from equilibrium profiles with less densely spaced rational surfaces of the dominant modes, which have been revealed by the recent progress in RFP research.抄録全体を表示PDF形式でダウンロード (240K) -
Yoshihiko Kurui, Yoshifumi Oshima, Kunio Takayanagi2007 年 76 巻 12 号 p. 123601
発行日: 2007/12/15
公開日: 2010/08/12
ジャーナル 認証ありUsing a transmission electron microscope combined with a scanning tunneling microscope, the relationship between structure and conductance of gold nanowires with axis along the [110] direction is investigated. The conductance histogram shows several high peaks and some subsidiary ones among them. The high peaks correspond to stable gold nanowires with a hexagonal cross section. The conductance peaks including the subsidiary peaks almost appear at integral multiples of the conductance quantum, G0 (=2e2⁄h), which is a direct evidence that these peaks are due to one-by-one evolution of conductance channel.抄録全体を表示PDF形式でダウンロード (173K) -
Kenichi Kato, Yutaka Moritomo, Hiroshi Tanaka, Hiroko Tokoro, Shin-ich ...2007 年 76 巻 12 号 p. 123602
発行日: 2007/12/15
公開日: 2010/08/12
ジャーナル 認証ありBased on the maximum entropy method (MEM) charge density, we have visualized the electrostatic potential of a charge-transfer compound, RbMn[Fe(CN)6], which shows the charge-transfer transition from the nominal Mn2+–Fe3+ configuration to the Mn3+–Fe2+ one below 220 K. In the low-temperature phase, the transferred electron spreads over the hexacyanoferrate ([Fe(CN)6]) via the strong Fet2g-CNπ* hybridization. Such an extended charge-transfer state is responsible for the relatively strong ferromagnetic coupling between the neighbouring Mn3+ spins.抄録全体を表示PDF形式でダウンロード (352K) -
Yasuhisa Yamamura, Kazuya Saito2007 年 76 巻 12 号 p. 123603
発行日: 2007/12/15
公開日: 2010/08/12
ジャーナル 認証ありTo study the phonon properties of β-ZrW2O8 showing the negative thermal expansion (NTE), the heat capacities of Zr1−xMxW2O8−y (M = Sc, Lu; x=0.02, 0.04) at low temperatures were measured and analyzed. The analysis presents the effective phonon density of states (DOS) of β-ZrW2O8, showing a rounded form around 5 meV. The rounded phonon DOS of β-ZrW2O8 is in marked contrast to that of the low-temperature phase of ZrW2O8, and their distinction is consistent with the difference in NTE nature between two structures.抄録全体を表示PDF形式でダウンロード (194K) -
Takahiko Sasaki, Hajime Oizumi, Naoki Yoneyama, Norio Kobayashi, Naoki ...2007 年 76 巻 12 号 p. 123701
発行日: 2007/12/15
公開日: 2010/08/12
ジャーナル 認証ありWe report X-ray irradiation-induced carrier doping effects on the electrical conductivity in the organic dimer–Mott insulators κ-(ET)2X with X = Cu[N(CN)2]Cl and Cu2(CN)3. For κ-(ET)2Cu[N(CN)2]Cl, we have observed a large decrease of the resistivity by 40% with the irradiation at 300 K and the metal-like temperature dependence down to about 50 K. The irradiation-induced defects expected at the donor molecule sites might cause a local imbalance of the charge transfer in the crystal. Such molecular defects result in the effective doping of carriers into the half-filled dimer–Mott insulators.抄録全体を表示PDF形式でダウンロード (265K) -
Kazuaki Kouyama, Yoshinori Kubo, Kazuhiro Ema, Hideki Kuwahara2007 年 76 巻 12 号 p. 123702
発行日: 2007/12/15
公開日: 2010/08/12
ジャーナル 認証ありWe investigate the time-dependent reflectivity of the layered manganite La0.5Sr1.5MnO4 at low temperature. We find that the reflectivity oscillates with an anomalously long period, e.g., several tens of hours. The period varies with wavelength and the character of the oscillation depends on the illumination condition. The oscillation is clearly observed below T∼20 K and almost disappears above this temperature. Furthermore, in the temperature-cycle measurements, the reflectivity oscillation shows a particularly peculiar behavior.抄録全体を表示PDF形式でダウンロード (398K) -
Akira Ochiai, Takaki Inukai, Takeshi Matsumura, Akira Oyamada, Kenichi ...2007 年 76 巻 12 号 p. 123703
発行日: 2007/12/15
公開日: 2010/08/12
ジャーナル 認証ありYbAl3C3 has been investigated in detail, which was previously reported to show an antiferroquadrupolar (AFQ) ordering at an extremely high ordering temperature of 80 K. The present study has revealed that the specific heat, magnetic susceptibility, and electrical resistivity of the single crystalline YbAl3C3 clearly exhibit the characteristic features of the first order transition around 77 K. In addition, we have discovered that LuAl3C3 also exhibits a sharp peak in the specific heat around 110 K, which most likely corresponds to the 77 K transition of YbAl3C3. Therefore, the 77 K transition of YbAl3C3 is considered to be irrelevant to the nature of the 4f-electrons such as the AFQ ordering but is ascribed to a structural one. Low temperature physical properties of YbAl3C3 below 77 K is indicative of a spin gap and a nonmagnetic ground state. A new model is proposed, in which the adjacent spins on the triangular lattice of Yb3+ ions are antiferromagnetically coupled to form a dimer by the structural transition at 77 K. The spin gap behavior at low temperatures can be well explained by an isolated dimer model with a singlet–triplet energy gap of about 15 K.抄録全体を表示PDF形式でダウンロード (263K) -
Atsushi Yamada, Toshiro Sakakibara, Jeroen Custers, Masato Hedo, Yoshi ...2007 年 76 巻 12 号 p. 123704
発行日: 2007/12/15
公開日: 2010/08/12
ジャーナル 認証ありAngle-resolved specific heat measurements are preformed on the f-electron superconductor CeRu2 in rotating magnetic fields 0.5≤H≤6 T at various temperatures 0.3≤T≤2 K. In the whole H–T range examined, a clear 4-fold oscillation is observed and yields the gap minimum (maximum) located to ⟨110⟩ (⟨100⟩) in the cubic crystal with the ratio Δmin⁄Δmax∼0.3. The oscillation amplitude landscape in H–T plane with a local maximum is explained by a microscopic theory, pointing to a new spectroscopy for gap determination.抄録全体を表示PDF形式でダウンロード (307K) -
Naoki Yoneyama, Takahiko Sasaki, Hajime Oizumi, Norio Kobayashi2007 年 76 巻 12 号 p. 123705
発行日: 2007/12/15
公開日: 2010/08/12
ジャーナル 認証ありWe report an impurity effect in the organic superconductor κ-(ET)2Cu(NCS)2 by substitution of the ET molecule with an analogue, bis(methylenedithio)tetrathiafulvalene (MT). The superconducting transition temperature decreases with increasing substitution. The in-plane magnetic penetration depth is enhanced with substitution, which is quantitatively attributed to the decrease in the in-plane mean free path. The enhancement of the penetration depth can also explain the reduction of the effective pinning in terms of the condensation energy.抄録全体を表示PDF形式でダウンロード (216K) -
Kozo Okada, Akio Kotani2007 年 76 巻 12 号 p. 123706
発行日: 2007/12/15
公開日: 2010/08/12
ジャーナル 認証ありThe present study theoretically shows that oxygen K resonant inelastic X-ray scattering (O K RIXS) in cuprates gives momentum-resolved information on the occupied and unoccupied electronic states. By tuning the incident X-ray energy carefully, we can select the k point where the X-ray absorption process as well as the subsequent X-ray emission process actually takes place. The requirement for the momentum specification is that the core-hole potential effect in the intermediate state of the RIXS should be negligible. This requirement is fulfilled only for the O K RIXS in the case of cuprates.抄録全体を表示PDF形式でダウンロード (772K) -
Takafumi Suzuki, Naoki Kawashima, Kohichi Okunishi2007 年 76 巻 12 号 p. 123707
発行日: 2007/12/15
公開日: 2010/08/12
ジャーナル 認証ありWe investigate the ordered state in S=1⁄2 XXZ spin chains with weak interchain couplings in a magnetic field by using quantum Monte Carlo simulations based on the directed-loop algorithm. The H–T phase diagram is illustrated for a square lattice and we find that an exotic spin-liquid state with quasi long-range incommensurate correlations in both the spin-chain and interchain directions may appear in the low-magnetization region without a finite-temperature transition. We also show that the incommensurate long-range-ordered state is stable for a cubic lattice.抄録全体を表示PDF形式でダウンロード (294K) -
Hiroyuki Chudo, Chishiro Michioka, Yutaka Itoh, Kazuyoshi Yoshimura2007 年 76 巻 12 号 p. 123708
発行日: 2007/12/15
公開日: 2010/08/12
ジャーナル 認証ありWe report 125Te and 139La NMR studies for single crystals of LaTe3 between 10 and 160 K under an applied field of H=7.4841 T. We observed the broad 125Te(1) NMR signals of metallic Te(1) sheets with a superlattice modulation and the sharp 125Te(2) and 139La NMR signals of LaTe(2) bi-layers. Temperature dependence of 125Te(1) nuclear spin–lattice relaxation times of the modulated Te(1) sheets obeys a modified Korringa relation. The results indicate that the electronic state on the Te(1) sheets is a Landau–Fermi liquid on a misfit superlattice or a Tomonaga–Luttinger liquid in a two-dimensional charge-density wave ordering state.抄録全体を表示PDF形式でダウンロード (189K) -
Yusuke Kousaka, Shin-ichiro Yano, Jun-ichiro Kishine, Yusuke Yoshida, ...2007 年 76 巻 12 号 p. 123709
発行日: 2007/12/15
公開日: 2010/08/12
ジャーナル 認証ありWe measured the anisotropic magnetization processes of copper metaborate CuB2O4 in detail. We propose an interpretation of the magnetization anomaly observed under the magnetic field applied perpendicular to the tetragonal axis, based on the field- and temperature-induced commensurate-to-incommensurate (C–IC) transition (Fréedericksz transition) accompanied by the chiral soliton lattice formation.抄録全体を表示PDF形式でダウンロード (1344K) -
Raquel de Almeida Ribeiro, Takahiro Onimaru, Kazunori Umeo, Marcos de ...2007 年 76 巻 12 号 p. 123710
発行日: 2007/12/15
公開日: 2010/08/12
ジャーナル 認証ありWe report on the electrical resistivity, magnetic susceptibility and heat-capacity measurements on a new intermetallic compound CePd5Al2, crystallizing in the ZrNi2Al5-type tetragonal structure, with lattice parameters a=4.156 Å and c=14.883 Å. The compound presents Kondo lattice behavior and an easy-plane antiferromagnetic ground state with two magnetic transitions at 2.9 and 3.9 K. The Sommerfeld coefficient is estimated as 60 mJ/(mol K2).抄録全体を表示PDF形式でダウンロード (934K) -
Dazu Huang, Zhigang Chen, Ying Guo, Moon Ho Lee2007 年 76 巻 12 号 p. 124001
発行日: 2007/12/15
公開日: 2010/08/12
ジャーナル 認証ありA quantum secure direct communication protocol based on chaos is proposed with authentication. It has an advantage over distributing the secret message directly and verifying the communicators’ identities with the assistance of a trusted center. To ensure the security of the secret message and the process of verification, the initial order of the travel particles is disturbed according to a chaotic sequence generated secretly via the general Arnold map. Security analysis demonstrates that the present scheme is secure against several attack strategies, such as the man-in-the-middle attack and Trojan horse attack.抄録全体を表示PDF形式でダウンロード (94K) -
Riki Kawashima, Toshiomi Miura, Hiroshi Isoda2007 年 76 巻 12 号 p. 124002
発行日: 2007/12/15
公開日: 2010/08/12
ジャーナル 認証ありTime series of ac conductivity were measured at 2 kHz in the temperature region from 200 to 8 K along a direction perpendicular to the c-axis for a praseodymium nitrate crystal. Nonperiodic instabilities (bursts) were found in all the time series. Their power spectral densities showed a continuous spectrum proportional to 1⁄fα. The correlation integrals were derived from the data. The temperature variation of both the power spectral densities and the correlation exponents at an embedding dimension was found in the three regions near 30, 80, and 150 K.抄録全体を表示PDF形式でダウンロード (3291K) -
Masa-aki Taniguchi, Masako Bando, Akihiro Nakayama2007 年 76 巻 12 号 p. 124003
発行日: 2007/12/15
公開日: 2010/08/12
ジャーナル 認証ありThe diffusion index DI announced by Bank of Japan has strong correlation with the economic growth ΔG. We propose a new economic model for ΔG and DI in order to explain the economic fluctuations. This model is described by equations analogous to the optimal velocity model in traffic flow. We solve the equations numerically and found that ΔG and DI fluctuate for a few years and converge to a fixed point finally. The predicted values for two or three years show a good agreement with the observed data. We also discuss the mathematical structure of our model.抄録全体を表示PDF形式でダウンロード (141K) -
Zhen-Yun Qin2007 年 76 巻 12 号 p. 124004
発行日: 2007/12/15
公開日: 2010/08/12
ジャーナル 認証ありBased on the Riemann theta function, the Hirota bilinear method is extended to directly construct periodic wave solutions of KdV–Sawada–Kotera equation. The relations among various data related to the Riemann theta functions are explicitly given by the Fourier series representation. The asymptotic property of the periodic wave solution of the KdV–Sawada–Kotera equation is analyzed in detail. It is shown that well-known soliton solution given by Hirota can be reduced from the periodic wave solution.抄録全体を表示PDF形式でダウンロード (340K) -
Shan-Tarng Chen, Hsen-Che Tseng, Shu-Chin Wang, Ping-Cheng Li2007 年 76 巻 12 号 p. 124005
発行日: 2007/12/15
公開日: 2010/08/12
ジャーナル 認証ありOur investigations focus on the various features of relevant element loops that have one element with two inputs. Such networks occur as relevant components of critical K=2 random Boolean networks. We have found many interesting results. Of them, one rather important outcome is that the mean number of attractors of the relevant element loops increases exponentially with the system size, yet the mean length of attractors increases at a power-law rate with the system size, but not faster than any power law.抄録全体を表示PDF形式でダウンロード (308K) -
Chhanda Samanta, Devasish Narayan Basu, Partha Roy Chowdhury2007 年 76 巻 12 号 p. 124201
発行日: 2007/12/15
公開日: 2010/08/12
ジャーナル 認証ありThe α-decay half lives of nuclei in the decay from element 277112 are calculated in a WKB framework using DDM3Y interaction and experimental Q-values. Theoretical estimation of half lives in the same quantum tunneling model, using Q-values from the mass formula of Muntian–Hofmann–Patyk–Sobiczewski, are also presented. Calculated results furnish corroborating evidence for the experimental findings at RIKEN and GSI. Certain discrepancies indicate necessity of a better mass formula. Further experimental data with higher statistics would also be useful.抄録全体を表示PDF形式でダウンロード (100K) -
Eisuke Magome, Mitsuo Machida, Yuuki Tamura, Masaru Komukae2007 年 76 巻 12 号 p. 124601
発行日: 2007/12/15
公開日: 2010/08/12
ジャーナル 認証ありTo study the isotope effect of glycinium phosphite (GPI), temperature dependences of the 50\\bar6 and 30\\bar10 structure factors of GPI and the 110\\bar3 and 90\\bar8 structure factors of deuterated GPI (DGPI) were analyzed in the ferroelectric phase by using the quasi-one-dimensional Ising model. The Ising model reproduces well the behavior of all the structure factors in the wide temperature region. The parameters for the intrachain and interchain interactions are determined to be 312 and 7.1 K for GPI, and 477 and 8.4 K for DGPI on average, respectively.抄録全体を表示PDF形式でダウンロード (191K) -
Masashi Watanabe, Yukio Noda, Yoshio Nogami, Hatsumi Mori2007 年 76 巻 12 号 p. 124602
発行日: 2007/12/15
公開日: 2010/08/12
ジャーナル 認証ありX-ray investigation of θ-BEDT-TTF2RbZn(SCN)4 was carried out around the temperature of the phase transition to the nonmagnetic state. θ-BEDT-TTF2RbZn(SCN)4 exhibits a metal–insulator transition accompanied by a charge ordering at TCO=200 K. In the one-dimensional spin chain formed by this charge ordering, BEDT-TTF donor molecules are aligned uniformly along the a-axis obeying the 21 screw symmetry of the space group P212121 below TCO. At the ground state, the system becomes nonmagnetic. The transition temperature Tc to the nonmagnetic phase seems to scatter around 20 K and may depend on the sample. We found that the extinction rule of [h00: h=2n] no longer applied below approximately 20 K. This indicated a symmetry breaking of the 21 screw symmetry along the a-axis in the nonmagnetic state. The observed peak intensities violating the extinction rule were about 10−4 of other general Bragg reflection peak intensities. This structural change should be interpreted as a spin-Peierls transition in the charge-ordered system. In addition, a corresponding anomaly was observed in the lattice parameter a.抄録全体を表示PDF形式でダウンロード (281K) -
Susumu Shimomura, Kazutoshi Torashima, Nobuyoshi Wakabayashi, Kengo Ni ...2007 年 76 巻 12 号 p. 124603
発行日: 2007/12/15
公開日: 2010/08/12
ジャーナル 認証ありX-ray diffraction measurements have been performed on Pr0.65Ca0.35MnO3 under hydrostatic pressure. Superlattice reflections due to charge and orbital order were measured at various temperatures and pressures. Above 2.1 GPa, the superlattice reflections disappear at low temperatures, showing a transition to a charge and orbital disordered phase. We found a pressure-induced phase characterized by a significant change in the intensity of the superlattice reflection. This phase shows reentrant transition behavior. Possible types of orders of the pressure-induced phase are discussed. The diffuse peaks associated with the short-range order observed under pressure is also presented.抄録全体を表示PDF形式でダウンロード (292K) -
Thuy-Trang Hua, Takashi Itoh, Susumu Fujiwara, Masato Hashimoto2007 年 76 巻 12 号 p. 124604
発行日: 2007/12/15
公開日: 2010/08/12
ジャーナル 認証ありVinylidene fluoride/trifluoroethylene (VDF/TrFE) copolymer crystals were grown from the dilute solution on cleaved (0001) surface of highly oriented pyrolytic graphite (HOPG). Using transmission electron microscopy, the orientational relation between the copolymer crystals and cleaved (0001) surface of HOPG is clarified, as well as the supperlattice matching. Electron diffraction (ED) patterns with 6-fold symmetry were observed for the copolymer crystals with VDF molar contents of 59, 65, and 71%. It suggests that a rectangular array of (20\\bar1) plane for the high-temperature phase (HP) of the copolymer crystal faces HOPG(0001) plane, from which the molecular chains tilt by 46.7°. The ED pattern with such 6-fold symmetry is attributed to superposition of diffractions from the HP crystallites with three different orientations on HOPG. Such results suggest that epitaxial growth of HP occurred and it was frozen or stabilized even at room temperature due to epitaxial effect or interaction between copolymer molecules and substrate atoms.抄録全体を表示PDF形式でダウンロード (857K) -
Katsuaki Kodama, Satoshi Iikubo, Shin-ichi Shamoto, Alexei A. Belik, E ...2007 年 76 巻 12 号 p. 124605
発行日: 2007/12/15
公開日: 2010/08/12
ジャーナル 認証ありWe have studied the local crystal structure of a multiferroic system BiMnO3 by means of atomic pair distibution function (PDF) analysis on neutron powder diffraction data. The domains with space group P2 or P21 whose atomic shifts break a symmetry of C-center exist in the bulk BiMnO3 with a space group C2, which is consistent with recent results of electron diffraction. The domain size is larger than 100 Å, also estimated by the PDF analysis. Because domains which have atomic shifts with different directions, typically the opposite direction, also exist, the bulk material “apparently” has a space group C2.抄録全体を表示PDF形式でダウンロード (810K) -
Takashi Tonegawa, Tôru Sakai, Kiyomi Okamoto, Makoto Kaburagi2007 年 76 巻 12 号 p. 124701
発行日: 2007/12/15
公開日: 2010/08/12
ジャーナル 認証ありEmploying numerical methods, we study the ground-state magnetization curve of a (S,S′)=(1,2) spin-alternating chain with uniaxial single-ion anisotropies, where S=1 and S′=2 spins are alternating and coupled antiferromagnetically. Special attention is paid to the magnetization plateau, the one-third plateau, which appears at one third of the saturation magnetization in the ground-state magnetization curve. We find that three kinds of one-third plateaux appear, one of which has a quantum nature, while the remaining two have a classical (Ising) nature. We determine the one-third plateau phase diagram on the D2 versus D1 plane, where D1 (D2) is the ratio of the single-ion anisotropy constant for the S=1 (S′=2) spin to the exchange interaction constant. This phase diagram consists of a phase boundary line between the quantum and classical one-third plateau states as well as three phase boundary lines between the one-third plateau and plateauless states. We emphasize that there is no phase transition between two classical one-third plateau states and both states are regarded as a single phase. Furthermore, the region of the one-third plateauless phase is divided into two parts, that is, the region in which the one-third magnetization state is not realized at any magnetic field as the ground state, and the region in which it is realized but no one-third plateau appears in the ground-state magnetization curve.抄録全体を表示PDF形式でダウンロード (242K) -
Yuriy P. Monarkha, Denis Konstantinov, Kimitoshi Kono2007 年 76 巻 12 号 p. 124702
発行日: 2007/12/15
公開日: 2010/08/12
ジャーナル 認証ありThe electron decay heating and linear dc resistivity of surface electrons (SEs) on liquid helium exposed to resonant microwave (MW) radiation are theoretically studied for the vapor atom scattering regime. Energy and momentum relaxation rates are generalized for an arbitrary electron distribution over the surface levels in order to obtain electron temperature and resistivity as functions of MW excitation rate. Even at very low excitation rates, electron temperature and dc resistivity are shown to increase rapidly with input power. At high excitation rates, electron temperature and MW resonance-induced resistivity saturate due to equating occupancies of the two lowest surface levels. Remarkably, hot-electron conditions with an electron temperature of approximately 30 K are provided by a very small fraction (about 10%) of SEs left on the ground and the first excited levels. These theoretical results agree with recent experimental observations.抄録全体を表示PDF形式でダウンロード (239K) -
Hideto Fukazawa, Taishi Okazaki, Kenji Hirayama, Yoh Kohori, Genfu Che ...2007 年 76 巻 12 号 p. 124703
発行日: 2007/12/15
公開日: 2010/08/12
ジャーナル 認証ありCe2MIn8 (M=Co, Rh) are heavy-fermion compounds: at ambient pressure, Ce2CoIn8 is a superconductor with TSC=0.4 K and Ce2RhIn8 is an antiferromagnet with TN=2.8 K and Ce2RhIn8 becomes superconducting below 1.4 K at 2.0 GPa. Their crystal structure can be viewed as successive layers of the heavy-fermion compounds CeMIn5 and CeIn3. In order to determine their physical properties, we perform a nuclear quadrupole resonance (NQR) measurement of 115In nuclei of Ce2MIn8. The spin–lattice relaxation rate 1⁄T1 of Ce2CoIn8 decreases with decreasing temperature T and is proportional to T through TSC. This is in contrast to the T1⁄2 dependence of the 1⁄T1 of pressurized Ce2RhIn8 above TSC.抄録全体を表示PDF形式でダウンロード (223K) -
Hiroyuki Kuroiwa, Yoshiki Imai, Tetsuro Saso2007 年 76 巻 12 号 p. 124704
発行日: 2007/12/15
公開日: 2010/08/12
ジャーナル 認証ありIn the analysis of the heavy electron systems, theoretical models with c–f hybridization gap are often used. We point out that such a gap does not exist and the simple picture with the hybridization gap is misleading in the metallic systems, and present a correct picture by explicitly constructing an effective band model of YbAl3. Hamiltonian consists of a nearly free electron model for conduction bands which hybridize with localized f-electrons, and includes only a few parameters. Density of states, Sommerfeld coefficient, f-electron number and optical conductivity are calculated and compared with the band calculations and the experiments.抄録全体を表示PDF形式でダウンロード (350K) -
Kazuya Yamamoto, Hitoshi Yamaoka, Naohito Tsujii, Aurel Mihai Vlaicu, ...2007 年 76 巻 12 号 p. 124705
発行日: 2007/12/15
公開日: 2010/08/12
ジャーナル 認証ありAn x-ray spectroscopy study was performed for YbCu5−xAlx (x=0.0–2.0) using high-resolution partial-fluorescence yield (PFY) and resonant inelastic x-ray scattering (RIXS) at the Yb L3 absorption edge. From a careful analysis of the PFY and RIXS spectra, the mean-valence of Yb was estimated and is found to increase quite rapidly for compositions between 0≤x≤1.0, indicating strong intermediate-valence behavior. The mean valence continues to increase gradually with x and becomes nearly trivalent for x=2.0. Our results, however, reveal that valence fluctuation occurs even at x=1.5, for which non-Fermi liquid quantum critical behavior is known. The valence evolution cannot be explained solely in terms of chemical pressure effects. The study suggests the role of valence-coupled spin fluctuations for the quantum critical behavior.抄録全体を表示PDF形式でダウンロード (395K) -
Roland Mathieu, Yoshinori Tokura2007 年 76 巻 12 号 p. 124706
発行日: 2007/12/15
公開日: 2010/08/12
ジャーナル 認証ありA macroscopic phase separation, in which ferromagnetic clusters are observed in an insulating matrix, is sometimes observed, and believed to be essential to the colossal magnetoresistive (CMR) properties of manganese oxides. The application of a magnetic field may indeed trigger large magnetoresistance effects due to the percolation between clusters allowing the movement of the charge carriers. However, this macroscopic phase separation is mainly related to extrinsic defects or impurities, which hinder the long-ranged charge–orbital order of the system. We show in the present article that rather than the macroscopic phase separation, an homogeneous short-ranged charge–orbital order accompanied by a spin glass state occurs, as an intrinsic result of the uniformity of the random potential perturbation induced by the solid solution of the cations on the A-sites of the structure of these materials. Hence the phase separation does occur, but in a more subtle and interesting nanoscopic form, here referred as “homogeneous”. Remarkably, this “nanoscale phase separation” alone is able to bring forth the colossal magnetoresistance in the perovskite manganites, and is potentially relevant to a wide variety of other magnetic and/or electrical properties of manganites, as well as many other transition metal oxides, in bulk or thin film form as we exemplify throughout the article.抄録全体を表示PDF形式でダウンロード (282K) -
Mikio Uruichi, Yue Yue, Kyuya Yakushi, Tomoyuki Mochida2007 年 76 巻 12 号 p. 124707
発行日: 2007/12/15
公開日: 2010/08/12
ジャーナル 認証ありWe present experimental findings showing that for npBifc-(F1TCNQ)3, two phases coexist over a wide temperature interval of 100–150 K near the monovalent-to-divalent phase transition temperature. Macroscopic domains of the high-temperature (monovalent) and low-temperature (divalent) phases were detected in the transition temperature region using X-ray diffraction and micro-Raman spectroscopy techniques. The volume fraction of the two domains continuously varied depending upon the temperature. A considerably large volume difference was found between the monovalent and divalent phases. The effect of volumetric strain due to this volume difference is discussed to understand this inhomogeneous state.抄録全体を表示PDF形式でダウンロード (472K) -
Ko-ichi Hiraki, Hadrien Mayaffre, Mladen Horvatic, Claude Berthier, Sh ...2007 年 76 巻 12 号 p. 124708
発行日: 2007/12/15
公開日: 2010/08/12
ジャーナル 認証ありWe performed 77Se NMR on a single crystal sample of the field-induced superconductor λ-(BETS)2FeCl4. Our result obtained in the paramagnetic state provide a microscopic insight on the exchange interaction J between the spins s of the BETS π conduction electrons and the Fe localized d spins S. The absolute value of the Knight shift K decreases when the polarization of the Fe spins increases. This reflects the “negative” spin polarization of the π electrons through the exchange interaction J. The value of J has been estimated from the temperature and the magnetic field dependence of K and found to be in good agreement with that deduced from transport measurements [Balicas et al.: Phys. Rev. Lett. 87 (2001) 067002]. This provides direct microscopic evidence that the field-induced superconductivity is due to the compensation effect predicted by Jaccarino and Peter [Phys. Rev. Lett. 9 (1962) 290]. Furthermore, an anomalous broadening of the NMR line has been observed at low temperatures, which suggests the existence of charge disproportionation in the metallic state neighboring the superconducting phase.抄録全体を表示PDF形式でダウンロード (585K) -
Youichi Yanase, Manfred Sigrist2007 年 76 巻 12 号 p. 124709
発行日: 2007/12/15
公開日: 2010/08/12
ジャーナル 認証ありThe paramagnetic properties in non-centrosymmetric superconductors with and without antiferromagnetic (AFM) order are investigated with focus on the heavy Fermion superconductors, CePt3Si, CeRhSi3, and CeIrSi3. First, we investigate the spin susceptibility in the linear response regime and elucidate the role of AFM order. The spin susceptibility at T=0 is independent of the pairing symmetry and increases in the AFM state. Second, the non-linear response to the magnetic field are investigated on the basis of an effective model for CePt3Si which may be also applicable to CeRhSi3 and CeIrSi3. The role of antisymmetric spin–orbit coupling (ASOC), helical superconductivity, anisotropic Fermi surfaces and AFM order are examined in the dominantly s-, p-, and d-wave states. We emphasize the qualitatively important role of the mixing of superconducting (SC) order parameters in the p-wave state which enhances the spin susceptibility and suppresses paramagnetic depairing effect in a significant way. Therefore, the dominantly p-wave superconductivity admixed with the s-wave order parameter is consistent with the paramagnetic properties of CePt3Si at ambient pressure. We propose some experiments which can elucidate the novel pairing states in CePt3Si as well as CeRhSi3 and CeIrSi3.抄録全体を表示PDF形式でダウンロード (344K) -
Kazuya Ishibashi, Kosuke Hamaguchi, Masato Okada2007 年 76 巻 12 号 p. 124801
発行日: 2007/12/15
公開日: 2010/08/12
ジャーナル 認証ありA synfire chain is a simple neural network model which can transmit stable synchronous spikes called a pulse packet. However how synfire chains coexist in one network remains to be elucidated. We have studied the activity of a layered associative network of leaky integrate-and-fire neurons which connections are embedded with memory patterns by the Hebbian learning rule. We analyze their activity by the Fokker–Planck method. In our previous report, when a half of neurons belongs to each memory pattern (pattern rate F=0.5), the temporal profiles of the network activity is split into temporally clustered groups called sublattices under certain input conditions. In this study, we show that when the network is sparsely connected (F<0.5), synchronous firings of the memory pattern are promoted. On the contrary, the densely connected network (F>0.5) inhibit synchronous firings. The basin of attraction and the storage capacity of the embedded memory patterns also depend on the sparseness of the network. We show that the sparsely (densely) connected networks enlarge (shrink) the basion of attraction and increase (decrease) the storage capacity.抄録全体を表示PDF形式でダウンロード (334K) -
Hideto Fukazawa, Kenji Hirayama, Takehiro Yamazaki, Yoh Kohori, Takehi ...2007 年 76 巻 12 号 p. 125001
発行日: 2007/12/15
公開日: 2010/08/12
ジャーナル 認証ありPDF形式でダウンロード (138K) -
Victor K. Kuetche, Thomas B. Bouetou, Timoleon C. Kofane2007 年 76 巻 12 号 p. 126001
発行日: 2007/12/15
公開日: 2010/08/12
ジャーナル 認証ありPDF形式でダウンロード (60K)
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