巻号一覧
77 巻, 3 号
選択された号の論文の54件中1～50を表示しています
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Shinji Yuasa2008 年 77 巻 3 号 p. 031001
発行日: 2008/03/15
公開日: 2011/12/28
ジャーナル 認証ありA magnetic tunnel junction (MTJ), which consists of a thin insulating layer (a tunnel barrier) sandwiched between two ferromagnetic electrode layers, exhibits tunneling magnetoresistance (TMR) due to spin-dependent electron tunneling. Since the discovery of room-temperature (RT) TMR effect in 1995, MTJs with an amorphous aluminum oxide (Al–O) tunnel barrier have been studied extensively. The Al–O-based MTJs exhibit magnetoresistance (MR) ratios up to about 70% at RT and are currently used in the read heads of hard disk drives and magnetoresistive random access memory (MRAM). MTJs with MR ratios significantly higher than 70% at RT, however, are needed for next-generation spintronic devices. In 2001, first-principle theories predicted that the MR ratios of epitaxial Fe/MgO/Fe MTJs with a crystalline MgO(001) barrier would be over 1000% because of the coherent tunneling of fully spin-polarized Δ1 electrons. In 2004, MR ratios of about 200% were obtained at RT in MTJs with a single-crystal MgO(001) barrier or a textured MgO(001) barrier. CoFeB/MgO/CoFeB MTJs for practical applications were also developed and found to have MR ratios up to 500% at RT. MgO-based MTJs are of great importance not only for device applications but also for clarifying the physics of spin-dependent tunneling.抄録全体を表示PDF形式でダウンロード (3338K) -
Yoshishige Suzuki, Hitoshi Kubota2008 年 77 巻 3 号 p. 031002
発行日: 2008/03/15
公開日: 2011/12/28
ジャーナル 認証ありA spin-polarized rf current injected into a magnetic cell exerts a torque to the local spin momenta and may excite ferromagnetic resonance (FMR) modes in the magnetic cell. FMR mode excitation in a magnetic tunnel junction is accompanied by the oscillation of its resistance and results a rectification effect. This “spin-torque diode effect” provides a quantitative measure of the spin-torque. By using this effect, the origin of the spin-torque and the critical voltage of spin-transfer magnetization switching were investigated. It is predicted that if the critical voltage becomes smaller than 25 mV, the spin-torque diode may have higher rectification output than p–n junction semiconductor diodes at room temperature. Also, the interplay between the giant tunneling magnetoresistance effect and the spin-torque will result in a negative differential resistance effect, and the magnetic tunneling junction may possess an amplification function.抄録全体を表示PDF形式でダウンロード (802K) -
Gen Tatara, Hiroshi Kohno, Junya Shibata2008 年 77 巻 3 号 p. 031003
発行日: 2008/03/15
公開日: 2011/12/28
ジャーナル 認証ありMicroscopic theory of domain wall dynamics under electric current is reviewed. Domain wall is treated as rigid and planar. The spin-transfer torque and forces on the wall are derived based on the s–d exchange interaction between localized spins and conduction electrons, treating non-adiabaticity expressed by the gauge field perturbatively. Effect of spin relaxation is also studied.抄録全体を表示PDF形式でダウンロード (884K) -
Roman Antos, YoshiChika Otani, Junya Shibata2008 年 77 巻 3 号 p. 031004
発行日: 2008/03/15
公開日: 2011/12/28
ジャーナル 認証ありWe review the recent theoretical and experimental achievements on dynamics of spin vortices in patterned ferromagnetic elements. We first demonstrate the theoretical background of the research topic and briefly list the analytical and experimental approaches dealing with magnetic vortices. Then we report on the most remarkable studies devoted to steady state vortex excitations, switching processes, and coupled-vortex dynamic phenomena including the design of artificial crystals where the micromagnetic energy transfer takes place via the magnetic dipolar interaction among excited vortices. Finally we summarize the present state of the research with respect to novel prospects from both the fundamental and the application viewpoints.抄録全体を表示PDF形式でダウンロード (1450K) -
Tomasz Dietl2008 年 77 巻 3 号 p. 031005
発行日: 2008/03/15
公開日: 2011/12/28
ジャーナル 認証ありThe presence of localized spins exerts a strong influence on quantum localization in doped semiconductors. At the same time carrier-mediated interactions between the localized spins are modified or even halted by carriers’ localization. The interplay of these effects is discussed for II–VI and III–V diluted magnetic semiconductors. This insight is exploited to interpret the complex dependence of resistance on temperature, magnetic field, and concentration of valence-band holes in (Ga,Mn)As. In particular, high field negative magnetoresistance results from the orbital weak localization effect. The resistance maximum and the associated negative magnetoresistance near the Curie temperature are assigned to the destructive influence of preformed ferromagnetic bubbles on the “antilocalization” effect driven by disorder-modified carrier–carrier interactions. These interactions account also for the low-temperature increase of resistance. Furthermore, the sensitivity of conductance to spin splitting and to scattering by spin disorder may explain resistance anomalies at coercive fields, where relative directions of external and molecular fields change.抄録全体を表示PDF形式でダウンロード (3508K) -
Yuichiro K. Kato, David D. Awschalom2008 年 77 巻 3 号 p. 031006
発行日: 2008/03/15
公開日: 2011/12/28
ジャーナル 認証ありElectrical manipulation of conduction band electron spins in nonmagnetic semiconductors is achieved by exploiting various manifestations of the spin–orbit interaction. The g-factor engineering combined with bandgap engineering leads to electrical tuning of the g-factor by changing the position of the electron wave function within parabolic quantum wells. Anisotropy of the g-tensor in these structures enables g-tensor modulation resonance through electrical control of the g-tensor. In a complementary approach, the momentum-dependent spin splitting in the conduction band manipulates spins. The strain-induced spin splitting is used to demonstrate coherent rotation of spins, even at zero magnetic field. The effective internal magnetic fields can also be used to drive spin resonance and to electrically polarize electron spins. Also originating from the spin–orbit interaction, the spin Hall effect generates a pure spin current transverse to an applied electric field even in the absence of applied magnetic fields.抄録全体を表示PDF形式でダウンロード (2530K) -
Markus König, Hartmut Buhmann, Laurens W. Molenkamp, Taylor Hughe ...2008 年 77 巻 3 号 p. 031007
発行日: 2008/03/15
公開日: 2011/12/28
ジャーナル 認証ありThe search for topologically non-trivial states of matter has become an important goal for condensed matter physics. Recently, a new class of topological insulators has been proposed. These topological insulators have an insulating gap in the bulk, but have topologically protected edge states due to the time reversal symmetry. In two dimensions the helical edge states give rise to the quantum spin Hall (QSH) effect, in the absence of any external magnetic field. Here we review a recent theory which predicts that the QSH state can be realized in HgTe/CdTe semiconductor quantum wells (QWs). By varying the thickness of the QW, the band structure changes from a normal to an “inverted” type at a critical thickness dc. We present an analytical solution of the helical edge states and explicitly demonstrate their topological stability. We also review the recent experimental observation of the QSH state in HgTe/(Hg,Cd)Te QWs. We review both the fabrication of the sample and the experimental setup. For thin QWs with well width dQW<6.3 nm, the insulating regime shows the conventional behavior of vanishingly small conductance at low temperature. However, for thicker QWs (dQW>6.3 nm), the nominally insulating regime shows a plateau of residual conductance close to 2e2⁄h. The residual conductance is independent of the sample width, indicating that it is caused by edge states. Furthermore, the residual conductance is destroyed by a small external magnetic field. The quantum phase transition at the critical thickness, dc=6.3 nm, is also independently determined from the occurrence of a magnetic field induced insulator to metal transition.抄録全体を表示PDF形式でダウンロード (959K) -
Makoto Kohda, Tobias Bergsten, Junsaku Nitta2008 年 77 巻 3 号 p. 031008
発行日: 2008/03/15
公開日: 2011/12/28
ジャーナル 認証ありSpin–orbit interaction (SOI), where the orbital motion of electrons is coupled with the orientation of electron spins, originates from a relativistic effect. Generally, in nonrelativistic momentum, p=hk<<m0c, the SOI is negligible. However, in a semiconductor heterostructure, the small energy-band gap (Eg<<m0c2) and the electron wave modulated by the atomic core potential markedly enhance the SOI. Since the SOI acts as an effective magnetic field, it may offer novel functionalities for controlling the spin degree of freedom such as the electrical spin generation and the electrical control of the spin precession in a semiconductor heterojunction. Here, we review recent experimental studies on the manipulation of the SOI in a semiconductor two-dimensional electron gas. We first present a theoretical overview of the Rashba SOI, which lifts the spin degeneracy due to structural inversion asymmetry. We then present experimental results on the quantum well (QW) thickness dependences of the Rashba SOI in InP/InGaAs/InAlAs asymmetric QWs by analyzing the weak antilocalization. Finally, we show quantum interference effects due to the spin precession in a small array of mesoscopic InGaAs rings, which is an experimental demonstration of the time-reversal Aharonov–Casher effect and the electromagnetic dual to the Al’tshuler–Aronov–Spivak effect.抄録全体を表示PDF形式でダウンロード (1462K) -
Saburo Takahashi, Sadamichi Maekawa2008 年 77 巻 3 号 p. 031009
発行日: 2008/03/15
公開日: 2011/12/28
ジャーナル 認証ありThe nonlocal spin transport in a nanostructure device consisting of ferromagnetic spin injector (F1) and spin detector (F2) electrodes connected to a normal conductor (N) or a superconductor (SC) is discussed. We explore how the spin transport in such a device depends on the nature of interface (metallic-contact or tunnel junction) and material parameters of electrodes by solving the spin-dependent transport equations, and obtain the conditions for efficient spin injection, spin accumulation, and spin current. In a device with SC, the spin transport is strongly affected by the onset of superconductivity. Nonlocal Spin Hall effect in metals and SCs are investigated. A superconducting qubit with a π junction is discussed.抄録全体を表示PDF形式でダウンロード (465K) -
Naoto Nagaosa2008 年 77 巻 3 号 p. 031010
発行日: 2008/03/15
公開日: 2011/12/28
ジャーナル 認証ありRecent theoretical developments on the physics of spin currents in semiconductors, metals and insulators are reviewed with the stress on the role of relativistic spin–orbit interaction. The key concept is the interplay between the electric field and spin current, which might enable the spintronics without magnetic field/magnets. We present this principle discussing spin Hall effect and multiferroic behavior as two realizations.抄録全体を表示PDF形式でダウンロード (445K) -
Seigo Tarucha, Jonathan Baugh2008 年 77 巻 3 号 p. 031011
発行日: 2008/03/15
公開日: 2011/12/28
ジャーナル 認証ありWe magnetically and electrically control spin coupling between electrons and nuclei in a vertical GaAs double quantum dot in the Pauli spin blockade regime to characterize the two-electron exchange energy and the dynamic nuclear polarization (DNP). The Pauli blockade is lifted by a hyperfine-mediated transition from an electron triplet state to the singlet state. This transition progressively occurs when the triplet-singlet separation or exchange energy J is compensated by tuning either Zeeman energy with external magnetic field (i.e., magnetic control) or inter-dot energy detuning with bias voltage (i.e., electrical control). The blockade is then lifted with a current step for sweeping up an external magnetic field. The J value, which is evaluated from the step position for various inter-dot detuning values, is consistent with calculation. DNP takes place through the hyperfine coupling near the current step, leading to a shifted current step to lower external magnetic field for the down-sweep. For the electrical control, a similar current step appears for sweeping bias voltage. In this case we are able to control the two-electron state energies in a relevant manner based on real time before DNP is significantly influenced, because the voltage sweep is much faster than the magnetic field sweep. We use this technique to distinguish the current step with and without DNP contributions, and therefore quantify the nuclear Overhauser fields with external magnetic field as a parameter. We present a simple phenomenological model to reproduce the experiment and also discuss a possible approach to realize the full DNP.抄録全体を表示PDF形式でダウンロード (3828K) -
Björn Trauzettel, Massoud Borhani, Mircea Trif, Daniel Loss2008 年 77 巻 3 号 p. 031012
発行日: 2008/03/15
公開日: 2011/12/28
ジャーナル 認証ありWe review recent advances on the theory of spin qubits in nanostructures. We focus on four selected topics. First, we show how to form spin qubits in the new and promising material graphene. Afterwards, we discuss spin relaxation and decoherence in quantum dots. In particular, we demonstrate how charge fluctations in the surrounding environment cause spin decay via spin–orbit coupling. We then turn to a brief overview of how one can use electric dipole spin resonance (EDSR) to perform single spin rotations in quantum dots using an oscillating electric field. The final topic we cover is the spin–spin coupling via spin–orbit interaction which is an alternative to the usual spin–spin coupling via the Heisenberg exchange interaction.抄録全体を表示PDF形式でダウンロード (1001K) -
Satoshi Tsutsui, Hisao Kobayashi, Daisuke Ishikawa, John P. Sutter, Al ...2008 年 77 巻 3 号 p. 033601
発行日: 2008/03/15
公開日: 2011/12/28
ジャーナル 認証ありMeasurements of S(Q,ω) of the filled skutterudite SmRu4P12 using inelastic x-ray scattering show a dispersionless mode at 9 meV. Meanwhile, the Sm partial phonon density of states measured by nuclear resonant inelastic scattering shows a strong peak at the same energy. The temperature dependence of the Sm phonon energy suggests that the Sm modes are anharmonic. The comparison of the experimental results in SmRu4P12 with the calculated ones in LaRu4P12 indicates the absence of any significant lattice instability due to 4f electrons.抄録全体を表示PDF形式でダウンロード (352K) -
Sho Tatsuoka, Hideyuki Sato, Kenya Tanaka, Makoto Ueda, Daisuke Kikuch ...2008 年 77 巻 3 号 p. 033701
発行日: 2008/03/15
公開日: 2011/12/28
ジャーナル 認証ありHigh-quality samples of LaFe4As12 with a residual resistivity ratio of 64 have been successfully synthesized under high pressure ∼4 GPa at 1100 K. The magnetization, specific heat, electrical resistivity, and Hall coefficient of the samples were measured. All the investigated properties exhibit evident anomalies at 5.2 K, thereby indicating a ferromagnetic transition. The large Rhodes–Wohlfarth ratio (≡ the ratio of the effective moment deduced from the Curie constant to the saturation moment per magnetic ion) of 32 suggests that LaFe4As12 is the first La-based filled skutterudite that exhibits itinerant-electron weak ferromagnetism, which is realized by the high density of states at the Fermi level D(EF). The ferromagnetism is unexpected within the simple Stoner-type argument, because D(EF) lies between those of an ordinary Pauli paramagnet LaFe4P12 and an enhanced Pauli paramagnet LaFe4Sb12 in the LaFe4X12 (X = P, As, Sb) series. We discuss this unexpected ferromagnetic transition on the basis of the difference in the spin-fluctuation strength between As- and Sb-based systems.抄録全体を表示PDF形式でダウンロード (804K) -
Masashige Matsumoto, Haruhiko Kuroe, Akira Oosawa, Tomoyuki Sekine2008 年 77 巻 3 号 p. 033702
発行日: 2008/03/15
公開日: 2011/12/28
ジャーナル 認証ありOne-magnon Raman scattering for interacting spin dimer systems is studied theoretically based on exchange light scattering process. We focus on a pressure-induced ordered phase, where a longitudinal excitation mode exists. We find that the Raman scattering probes the longitudinal mode selectively. The Raman intensity is finite only in the ordered phase and develops with pressure. We apply the theory to spin gapped systems such as TlCuCl3 and NiCl2–4SC(NH2)2 to demonstrate that the Raman scattering is a suitable probe for the longitudinal mode.抄録全体を表示PDF形式でダウンロード (115K) -
Jin-Seok Jeon, Chansoo Lim, Ho-Young Kwak2008 年 77 巻 3 号 p. 033703
発行日: 2008/03/15
公開日: 2011/12/28
ジャーナル 認証ありThe pulse widths of sonoluminescing gas bubbles in a sulfuric acid solution were precisely measured by using the time-correlated single-photon counting method, which has not been attempted previously. The pulse widths, which are dependent on the size of the bubble at the collapse point were measured and found to be in the range of 165 ps to several ns. The value of the pulse width calculated by assuming thermal bremsstrahlung as the emission mechanism of the sonoluminescence was found to be larger than the observed value by an order of magnitude.抄録全体を表示PDF形式でダウンロード (433K) -
Akihisa Koga, Norio Kawakami, Robert Peters, Thomas Pruschke2008 年 77 巻 3 号 p. 033704
発行日: 2008/03/15
公開日: 2011/12/28
ジャーナル 認証ありWe study the magnetic properties of the extended periodic Anderson model, which includes the electron correlations within and between the itinerant and localized bands. By combining dynamical mean-field theory with the numerical renormalization group, we calculate the sublattice magnetization and the staggered susceptibility to determine the phase diagram in the particle–hole symmetric case. We find that two kinds of magnetically ordered states compete with the Kondo insulating state at zero temperature, which induces non-monotonic behavior in the temperature-dependent magnetization. We also clarify that a novel magnetic metallic state is stabilized at half filling by the competition between Hund’s coupling and the hybridization.抄録全体を表示PDF形式でダウンロード (172K) -
Shunji Sugai, Yasumasa Takayanagi, Naoki Hayamizu, Tsuyoshi Muroi2008 年 77 巻 3 号 p. 033705
発行日: 2008/03/15
公開日: 2011/12/28
ジャーナル 認証ありIn La2−xSrxCuO4 the superconducting gap energy in the B2g Raman spectra is almost constant from the optimum doping to near the insulator–metal (I–M) transition, indicating that the gap symmetry is s or d(xy), because the Fermi arc shrinks into the nodal direction of the d(x2−y2) gap. The reason of the different result from other experiments comes from the dual components of the low-energy electronic states around (π⁄2,π⁄2), the resonant peak relating to the I–M transition and the polaron states. The superconducting coherent peak is found to be created only in the polaron states in the underdoped phase.抄録全体を表示PDF形式でダウンロード (686K) -
Yoshiaki Shimada, Haruki Kiyama, Yoshinori Tokura2008 年 77 巻 3 号 p. 033706
発行日: 2008/03/15
公開日: 2011/12/28
ジャーナル 認証ありThe nonreciprocal directional dichroism derived from the optical magnetoelectric effect has been investigated for the f–f transitions of Nd3+ ion in a ferroelectric Nd2Ti2O7 single crystal under magnetic field, in which both space-inversion and time-reversal symmetries are viewed as simultaneously broken. The magnitude of nonreciprocity in each absorption band of Nd3+ was semi-quantitatively elucidated by taking account of the interference between electric dipole and magnetic dipole transitions.抄録全体を表示PDF形式でダウンロード (262K) -
Shinya Tsukada, Yuji Ike, Jun Kano, Tadashi Sekiya, Yoshiro Shimojo, R ...2008 年 77 巻 3 号 p. 033707
発行日: 2008/03/15
公開日: 2011/12/28
ジャーナル 認証ありDynamical properties of the polar nanoregions (PNRs) of a relaxor ferroelectric Pb(Ni1⁄3Nb2⁄3)O3–0.29PbTiO3 single crystal are studied by using Brillouin scattering to elucidate the mechanism of the diffuse phase transition. The temperature dependence of Brillouin scattering shows anomalies at three temperatures: at Td related to the appearance of the PNRs, at T* associated with the growth of the PNRs, and at Tf related to the macroscopic structural phase transition; all these temperatures are closely related to the dynamical behavior of the PNRs. The thermal hysteresis around Tf in the longitudinal acoustic properties can be interpreted by considering the growth process of the PNRs. From the anomalous acoustic properties, the relaxation time of the polarization fluctuation is evaluated. It is found that the relaxational process responsible for the central peak originates from the polarization fluctuation that is coupled with the longitudinal acoustic mode.抄録全体を表示PDF形式でダウンロード (308K) -
Gyuchang Lim, Soo Yong Kim, Kyungsik Kim, Dong-In Lee, Myung-Kul Yum2008 年 77 巻 3 号 p. 033801
発行日: 2008/03/15
公開日: 2011/12/28
ジャーナル 認証ありThe inter-out-of-equilibrium state interval is analyzed in order to detect determinism in financial markets. We divide the time series of the return for price increments into two phases, equilibrium and out-of-equilibrium phases, due to two phase phenomena. Using an attractor reconstructed from a singular time series via Takens’ theorem, the nonlinearity and determinism of inter-out-of-equilibrium state intervals are closely examined. Assuming an extended integrate-and-fire model analogous to fractional Brownian motion, a one-to-one correspondence is identified between the underlying system states and the reconstructed inter-out-of-equilibrium state interval vectors of a certain dimension. As compared to typical models driven by deterministic or stochastic processes, the inter-out-of-equilibrium state interval in the financial markets is found to exhibit features similar to stochastic properties.抄録全体を表示PDF形式でダウンロード (111K) -
Shinya Saka, Hiroshi Takano2008 年 77 巻 3 号 p. 034001
発行日: 2008/03/15
公開日: 2011/12/28
ジャーナル 認証ありThe relaxation of a single knotted ring polymer is studied by Brownian dynamics simulations. The relaxation rate λq for the wave number q is estimated by the least square fit of the equilibrium time-displaced correlation function \\hatCq(t)=N−1∑i∑j(1⁄3)‹Ri(t)·Rj(0)›exp[i2πq(j−i)⁄N] to a double exponential decay at long times. Here, N is the number of segments of a ring polymer and Ri denotes the position of the ith segment relative to the center of mass of the polymer. The relaxation rate distribution of a single ring polymer with the trivial knot appears to behave as λq\\simeqA(1⁄N)x for q=1 and λq\\simeqA′(q⁄N)x′ for q>1, where x\\simeq2.10, x′\\simeq2.17, and A<A′. These exponents are similar to that found for a linear polymer chain. The topological effect appears as the separation of the power law dependences for q=1 and q>1, which does not appear for a linear polymer chain. In the case of the trefoil knot, the relaxation rate distribution appears to behave as λq\\simeqA(1⁄N)x for q=1 and λq\\simeqA′(q⁄N)x′ for q=2 and 3, where x\\simeq2.61, x′\\simeq2.02, and A>A′. The wave number q of the slowest relaxation rate λq for each N is given by q=2 for small values of N, while it is given by q=1 for large values of N. This crossover corresponds to the change of the structure of the ring polymer caused by the localization of the knotted part to a part of the ring polymer.抄録全体を表示PDF形式でダウンロード (656K) -
Zhen-Yun Qin2008 年 77 巻 3 号 p. 034002
発行日: 2008/03/15
公開日: 2011/12/28
ジャーナル 認証ありRecently, Mukherjee, Choudhury, and Chowdhury presented a new discrete integrable system. Based on its Lax pairs, we construct infinitely many conservation laws and Darboux transformation for the discrete system. As an application of the Darboux transformation, we carry out a new exact solution of the discrete system.抄録全体を表示PDF形式でダウンロード (483K) -
Hiroyuki Tanaka, Keiji Miura, Masato Okada2008 年 77 巻 3 号 p. 034003
発行日: 2008/03/15
公開日: 2011/12/28
ジャーナル 認証ありThe Gaussian model for image restoration has the problem of positive probability densities for pixels outside the realistic range. To solve this problem, we introduce a truncated Gaussian model (TG model). In this model, the tails of the Gaussian distribution are cut off at upper and lower bounds and are replaced by δ peaks at the cut boundaries. We analytically obtain the average performance of the TG model in a mean-field system by solving exactly the infinite-range model and using the replica method. We also compare the infinite-range model to the more realistic two-dimensional case by Monte Carlo simulations. When modeling the TG model, we introduce a generalized prior probability. This prior probability includes the Gaussian, Ising, Q-Ising spin, and TG model as special cases. Thus, we can choose an appropriate model depending on the statistical properties of the images.抄録全体を表示PDF形式でダウンロード (1585K) -
Fu-Rong Ding, Ping Shi, Rui Nie, Hong-Ji Ma2008 年 77 巻 3 号 p. 034301
発行日: 2008/03/15
公開日: 2011/12/28
ジャーナル 認証ありA sample for studying secondary ion emissions was made by pressing powders of carbon nanotubes with purity of 98%. The emission yields of different species of atoms/molecules are measured by using a conventional time of flight (TOF) technique under bombardments of C+q, Si+q (q=1–6), and Ni+q (q=1–5), C2+q, Si2+q (q=1,3,5), and Ni2+q (q=3,5), C3+q, Si3+q, and Ni3+q (q=2,4) with energy of 1.5 MeV per atom, respectively. With increasing charge states of the projectiles, the secondary ion emission yields per projectile increase and q3-dependence are observed. The size and the charge state of the clusters are larger, the secondary ion emissions are more enhanced. The electronic process plays an important role in secondary ion emissions under fast projectile bombardments.抄録全体を表示PDF形式でダウンロード (242K) -
Eiichi Hanamura, Jun Kato, Kuon Inoue, Yukito Tanabe2008 年 77 巻 3 号 p. 034401
発行日: 2008/03/15
公開日: 2011/12/28
ジャーナル 認証ありWe have observed the originally Raman-inactive phonon at the Brillouin zone (BZ) edge as multistep coherent anti-Stokes Raman scattering signals in a series of directions in which the phase-matching conditions are apparently broken under resonant pumping of the overtone of these phonons. The two anomalous behaviors of (1) breaking the Raman-selection rule and (2) the phase-matching-free signals, have been theoretically resolved by introducing a model of folding the BZ edge onto the Γ-point and the periodic modulation of the dielectric function with the wavevector of the condensed phonons. This model is shown to make the observed results well understood.抄録全体を表示PDF形式でダウンロード (162K) -
Jun’ichi Wakou, Akinori Ochiai, Masaharu Isobe2008 年 77 巻 3 号 p. 034402
発行日: 2008/03/15
公開日: 2011/12/28
ジャーナル 認証ありWe present a Langevin approach to describe the steady-state dynamics of one-dimensional granular media fluidized by a vibrating bottom plate. We adopt a linear Langevin equation to describe the motion of the center of mass. Within this framework, we derive analytical expressions for several macroscopic quantities. We also predict the power spectrum for the height of the center of mass. We find good agreement between our theoretical predictions and extensive event-driven molecular dynamics simulations.抄録全体を表示PDF形式でダウンロード (1323K) -
Shunji Nojima, Yusuke Kamakura2008 年 77 巻 3 号 p. 034403
発行日: 2008/03/15
公開日: 2011/12/28
ジャーナル 認証ありDetailed calculations are carried out for band structures in the whole area of the first Brillouin zone (BZ) for two-dimensional binary-compound photonic crystals (PCs) with the square lattice. This kind of PCs is shown to alter its irreducible BZ, depending on the position of the second atom, because of the introduction of the spatial anisotropy into the unit cell. In particular, the PCs with very asymmetric atomic configurations are forced to render the whole first BZ irreducible. Only the investigation throughout the BZ is thus known to permit us to obtain the authentic band structures for this kind of PCs.抄録全体を表示PDF形式でダウンロード (2429K) -
Ken Uzawa, Yasuaki Kishimoto, Jiquan Li2008 年 77 巻 3 号 p. 034501
発行日: 2008/03/15
公開日: 2011/12/28
ジャーナル 認証ありThe effects of an external mean flow on the modulational instability process of zonal flow in drift wave turbulence are theoretically studied based on Hasegawa–Mima (HM) turbulence model. Based on the coherent mode coupling approach, a dispersion relation of the zonal flow instability involving the external mean flow with a wave-type characterized by the amplitude |φf|, radial wave number kf, and frequency ωf is derived. As an example, the zonal flow driven by ion temperature gradient (ITG) turbulence is sampled as the mean flow acting on the modulational process of zonal flow instability in electron temperature gradient (ETG) turbulence. It is shown that the growth rate of the zonal flow, γq, is suppressed by the mean flow with a fitting relation γq\\simeqγq0−α|φf|2k2f, where γq0 is the growth rate of the zonal flow in the absence of mean flow and α is a positive numerical constant. This formula is applicable to a strong shearing regime where the zonal flow instability is stabilized. The suppression mechanism is investigated and found to originate from frequency mismatch due to an increase of the real frequency of zonal flow |Ωq|.抄録全体を表示PDF形式でダウンロード (411K) -
Jun Kondo2008 年 77 巻 3 号 p. 034601
発行日: 2008/03/15
公開日: 2011/12/28
ジャーナル 認証ありA heavy atom enclosed in a large cage and interacting with metal electrons is considered. The interaction between the atom and the electrons causes a shift of the atomic energy levels. When the level spacing is smaller than kBT, the shift turned out to vary with temperature according to logT. We consider a model, where the cage is represented by a potential of eight wells which are located at eight corners of a cube. We assume there is a localized “atomic” orbital at each well and a transfer integral between nearest neighbouring orbitals is considered. The electron–atom interaction renormalizes the transfer integral. The normalization factor involves logT and is the same as that in a two well problem.抄録全体を表示PDF形式でダウンロード (73K) -
Annamária Kiss, Yoshio Kuramoto2008 年 77 巻 3 号 p. 034602
発行日: 2008/03/15
公開日: 2011/12/28
ジャーナル 認証ありBy phenomenological Landau analysis, it is shown that a scalar order parameter with the point-group symmetry Γ1g explains most properties associated with the phase transition in PrFe4P12 at 6.5 K. The scalar-order model reproduces magnetic and elastic properties in PrFe4P12 consistently such as (i) the anomaly of the magnetic susceptibility and elastic constant at the transition temperature, (ii) anisotropy of the magnetic susceptibility in the presence of uniaxial pressure, and (iii) the anomaly in the elastic constant in magnetic field. An Ehrenfest relation is derived which relates the anomaly of the magnetic susceptibility to that of the elastic constant at the transition.抄録全体を表示PDF形式でダウンロード (255K) -
Kenji Maruyama, Hirohisa Endo, Hideoki Hoshino2008 年 77 巻 3 号 p. 034603
発行日: 2008/03/15
公開日: 2011/12/28
ジャーナル 認証ありThe reverse Monte Carlo (RMC) and Voronoi–Delaunay analyses have been applied to derive the void-based partial pair distribution functions g′Te–Te(r), g′V–Te(r), and g′V–V(r), the partial coordination number distributions P(NTeTe), P(NVTe), and P(NVV), and the bond angle and dihedral angle in l-Te to clarify the connectivity of the covalently bonded Te chains supporting voids. The P(NTeTe) reveals that shorter and longer interchain bonds coexist. Large fluctuations in the interchain distance create the small voids (2.5 Å in radius) supported by stacked chains and the large voids (3.1 Å in radius) supported by rings of ∼8 Te atoms. The number of Te rings increases with increasing temperature. It is found that the inter-Te ring correlation dominates the intermediate-range chemical ordering of voids–Te atoms and voids–voids in l-Te, which is responsible for a small shoulder on the leading edge of the principal peak of S(Q).抄録全体を表示PDF形式でダウンロード (703K) -
Daisuke Nishioka, Koichi Nakamura, Yoshitaka Michihiro, Takashi Ohno, ...2008 年 77 巻 3 号 p. 034604
発行日: 2008/03/15
公開日: 2011/12/28
ジャーナル 認証ありThe mechanism of superionic conductivity in β-LiGa has been investigated by 7Li and 71Ga NMR spin–lattice relaxation rates 1⁄T1 in Li excess 50.0 at. %, Li deficient 44.0 and 47.0 at. % samples. The activation energies of Li+ ionic diffusions through free Li vacancy VLi and through bound Li vacancy trapped by antisite LiGa have been estimated to be 0.13 and 0.064 eV by applying Bloembergen–Purcell–Pound (BPP) type equation to 1⁄T1 in 50.0 at. % Li sample. In Li deficient samples, the same activation energy, 0.11–0.13 eV, for Li+ ionic diffusion through free VLi has been obtained at high temperatures, and evidence for the ordering of VLi has been also detected by anomalies at 200–240 K in the temperature dependence of 1⁄T1 for 7Li. However, the motional narrowing observed in 7Li NMR line width above 110–130 K indicates that disorder in VLi can still remain even below its ordering temperature in 44.0 and 47.0 at. % Li samples.抄録全体を表示PDF形式でダウンロード (400K) -
Tomonari Sumi, Hideo Sekino2008 年 77 巻 3 号 p. 034605
発行日: 2008/03/15
公開日: 2011/12/28
ジャーナル 認証ありA self-consistent density-functional theory (DFT) for homogeneous and inhomogeneous classical fluids is presented using the density-functional Taylor expansion of an effective density that is introduced to describe the intrinsic excess free-energy functional. The first-order density expansion of the effective density around the uniform bulk density provides the same intrinsic excess chemical potential as the weighted density-functional approach proposed by Patra and Ghosh [J. Chem. Phys. 116 (2002) 8509]. The density-expansion coefficient is determined in a self-consistent manner by using Percus’ relation between the pair correlation function and the density distribution function. The pair correlation functions for hard-sphere (HS) and Lennard-Jones (LJ) fluids as well as one-component plasma obtained from the self-consistent DFT are compared with the simulation results. The DFT with the self-consistent expansion coefficient is applied to calculate density distribution functions for the inhomogeneous fluids, interacting via the HS and LJ potentials, under external fields such as confinement in several geometries.抄録全体を表示PDF形式でダウンロード (204K) -
Salah A. M. El Shourbagy, Shiro Okeda, Hans-Georg Matuttis2008 年 77 巻 3 号 p. 034606
発行日: 2008/03/15
公開日: 2011/12/28
ジャーナル 認証ありWe investigate the sound velocity of assemblies of granular particles. Computationally, we investigate regular polygons with various corner numbers in two dimensions with the discrete element method and compare the results for large corner numbers with experiments on soft air-gun beads. The sound velocity for one-dimensional granular chains of spherical particles is about one order of magnitude less than the sound velocity of the bulk material, both in the simulation as well as in the experiment. For two-dimensional simulations, the results are comparable to that for one-dimensional chains, but vary with the packing. For the experiments in three dimensions, we find that the sound velocity is two orders of magnitude less than that of the bulk, or one order of magnitude less than that for one- or two-dimensional systems. This result is consistent with the group velocity reported by Liu and Nagel, but well below their reported “sound velocity”. The latter was in all likelihood not a linear (amplitude-independent) sound wave but one for which the sound-velocity was already affected by non-linear effects, as we elaborate on experimental, theoretical and computational considerations.抄録全体を表示PDF形式でダウンロード (2875K) -
Takayuki Kawamata, Nobuo Takahashi, Tadashi Adachi, Takashi Noji, Kazu ...2008 年 77 巻 3 号 p. 034607
発行日: 2008/03/15
公開日: 2011/12/28
ジャーナル 認証ありWe have measured the thermal conductivity of the one-dimensional (1D) S=1⁄2 Heisenberg antiferromagnetic spin system of Sr2Cu1−xPdxO3 single crystals including nonmagnetic impurities of Pd2+. It has been found that the mean free path of spinons along the 1D spin chain at low temperatures is very close to the average length of finite spin chains between spin defects estimated from the magnetic susceptibility measurements. This proves that the thermal conduction due to spinons at low temperatures in Sr2CuO3 is ballistic as theoretically expected [Zotos et al.: Phys. Rev. Lett. 55 (1997) 11029].抄録全体を表示PDF形式でダウンロード (241K) -
Yasunobu Nakamura, Takeo Takagi2008 年 77 巻 3 号 p. 034608
発行日: 2008/03/15
公開日: 2011/12/28
ジャーナル 認証ありWe confine several 4He particles in a nanoscale-radius spherical cage. The effective inner radius of the cage ranges from 3.5 to 10.0 Å. We construct a simplified model for the system, and compute its thermodynamic quantities by an imaginary time path integral method. In this computation, we deal with 4He particles as not only Bose particles but also distinguishable particles in order to clarify the role of particle statistics. In the boson case, kinetic energy strongly depends on the number of confined particles and cage radius. The energy difference between two statistics cases becomes considerably large in the temperature region T<2.0 K. The energy difference reflects the particle exchange effect, and we evaluate the solidification condition of the system.抄録全体を表示PDF形式でダウンロード (169K) -
Limin Wang, Zhenxing Liu, Weiyi Zhang2008 年 77 巻 3 号 p. 034701
発行日: 2008/03/15
公開日: 2011/12/28
ジャーナル 認証ありA comparative study is made on the localization and scaling behavior in piezomagnetic Fibonacci and symmetric Fibonacci-class [SFC(n)] superlattices. For this photon–phonon coupled system, the polaritonic band-gap structures and transmission spectra both show a pattern of self-similarity, the fractal pattern in transmission spectra clearly demonstrates the (quasi)localization nature of polaritons. For Fibonacci superlattices self-similarity behavior takes place between the lth and the (l+3)th generations, the scaling index α′=τ3=4.236 with τ=0.5(\\sqrt5+1) denoting the golden mean. While for the generalized symmetric Fibonacci-class [SFC(n)] superlattices, self-similarity behavior occurs between the lth and the (l+1)th generations and the scaling index α″=0.5(n+\\sqrtn2+4). We conclude that the internal symmetric structure is responsible for the evolution of such scaling behavior.抄録全体を表示PDF形式でダウンロード (310K) -
Satoru Miyaki, Kenji Makoshi, Hiroyasu Koizumi2008 年 77 巻 3 号 p. 034702
発行日: 2008/03/15
公開日: 2011/12/28
ジャーナル 認証ありMulticonfiguration molecular orbital cluster calculation results combined with experimental observations suggest that the local electronic state unit for a doped hole contains at least two Cu atoms in contrast to the Zhang–Rice singlet state that includes only one Cu atom. The cluster calculation shows that a doped hole in a two copper containing cluster induces a pseudo Jahn–Teller instability with stabilization energy that agrees with a peak in the photoinduced conductivity measurement, and the Cu–O bond length fluctuations that explain the EXAFS experiment; the charge-transfer energy gap observed in the optical conductivity measurement, and an excitation energy that corresponds to a peak in the energy loss function are also obtained from the calculation including two Cu atoms.抄録全体を表示PDF形式でダウンロード (153K) -
Makoto Iwata, Zdravko Kutnjak, Yoshihiro Ishibashi, Robert Blinc2008 年 77 巻 3 号 p. 034703
発行日: 2008/03/15
公開日: 2011/12/28
ジャーナル 認証ありThe temperature–field phase diagrams are discussed within the Landau theory for perovskite-type ferroelectrics, which undergo successive transitions of first order. The sequences of the cubic–tetragonal–orthorhombic–rhombohedral phases and the cubic–rhombohedral–orthorhombic–tetragonal phases are considered, and the field is applied along the [100], [110], or [111] direction. The topology of the phase diagrams obtained are found to depend much on the degree of the anisotropy of the Landau potential functions in the order parameter space. When the free energy function is nearly isotropic, the critical end points associated with all the possible ferroelectric phases, stabilized successively with decreasing temperature, appear at a certain field and temperature. Only the one associated with the highest temperature ferroelectric phase does that at a fairly high field. It is pointed out that the critical end points experimentally observed in the relaxor ferroelectrics like Pb(Mg1⁄3Nb2⁄3)O3 suggests that the transition in the relaxor, if any, must be of first order.抄録全体を表示PDF形式でダウンロード (196K) -
Eiki Kabasawa, Jin Nakamura, Nobuyoshi Yamada, Kazuhiko Kuroki, Hisash ...2008 年 77 巻 3 号 p. 034704
発行日: 2008/03/15
公開日: 2011/12/28
ジャーナル 認証ありThe polarization dependence of soft x-ray absorption spectroscopy (XAS) and x-ray emission spectroscopy (XES) near the O 1s absorption edge was measured on two-leg ladder single-crystalline samples of (Sr,Ca,Y,La)14Cu24O41 (14-24-41). The hole distributions in 14-24-41 compounds are determined by polarization analysis. For samples with less than or equal to 5 holes/chemical formula (c.f.), all holes reside on the edge-shared chain layer. In the case of Sr14−xCaxCu24O41 (6 holes/c.f.), there is approximately one hole on the two-leg ladder layer, with about five holes remaining on the edge-shared chain layer. By Ca substitution for Sr in the Sr14−xCaxCu24O41 samples, 0.3 holes transfer from the edge-shared chain to the two-leg ladder layer. It is possible that some of the holes on the two-leg ladder layer move from the rung sites to the leg sites upon Ca substitution.抄録全体を表示PDF形式でダウンロード (729K) -
Denis Konstantinov, Hanako Isshiki, Hikota Akimoto, Keiya Shirahama, Y ...2008 年 77 巻 3 号 p. 034705
発行日: 2008/03/15
公開日: 2011/12/28
ジャーナル 認証ありA resonance-induced change is observed in the resistivity of surface state electrons (SSEs) exposed to microwave (MW) radiation. The MW frequency corresponds to the transition energy between the two lowest Rydberg energy levels. All measurements are performed with electrons on liquid 3He in the temperature range 0.45–0.65 K in which the electron relaxation time and the MW absorption linewidth are determined by the collisions of the electrons with helium vapor atoms. The resistivity is found to increase in the vicinity of the MW resonance at all values of the input MW power which is varied by two orders of magnitude. This effect is attributed to the heating of SSEs by the resonance MW radiation. The temperature and the momentum relaxation rate of the hot electrons are calculated as a function of the MW power in the cell, and the Rabi frequency is determined from a comparison of the theoretical result with the experiment. In addition, the broadening of the absorption signal caused by the heating is studied experimentally, and the results are found to be in good agreement with our calculations.抄録全体を表示PDF形式でダウンロード (609K) -
Masashi Hase, Hideaki Kitazawa, Kiyoshi Ozawa, Tomoaki Hamasaki, Haruh ...2008 年 77 巻 3 号 p. 034706
発行日: 2008/03/15
公開日: 2011/12/28
ジャーナル 認証ありWe studied the effects of Zn doped into Cu sites on the magnetism of Cu3Mo2O9. The spin system consists of spin-1/2 antiferromagnetic (AF) uniform chains and AF dimers. Each chain is coupled to neighboring dimers by other interactions, giving rise to magnetic frustration. A component parallel to the chain of magnetic moment in the chain forms AF long-range order (LRO) below the transition temperature TN, whereas a perpendicular component is disordered in zero magnetic field and above 2.0 K. The perpendicular component forms weak ferromagnetic LRO (WF-LRO) only in finite magnetic fields H’s. We have found that WF-LRO in H disappears with a very small amount of Zn doping, although the decrease of TN is negligible at corresponding Zn concentrations. These results are explained by the enhancement of magnetic frustration among symmetric exchange interactions caused by Zn doping.抄録全体を表示PDF形式でダウンロード (143K) -
Kiminori Hattori2008 年 77 巻 3 号 p. 034707
発行日: 2008/03/15
公開日: 2011/12/28
ジャーナル 認証ありThis paper analyzes spin currents pumped from Rashba spin–orbit coupled two-dimensional electron systems in electric dipole spin resonance (EDSR), on the basis of the nonequilibrium Green’s function formalism. In the ballistic transport regime, the EDSR-induced spin pumping efficiently occurs for the finite-sized system smaller than the spin precession length. In the diffusive transport regime, the spin pumping is remarkably enhanced with increasing static disorder while the pumped spin dephases to a certain degree due to the D’yakonov–Perel’ mechanism. The spin dephasing is controlled by reducing the system size compared with the precession length irrespective of the degree of disorder.抄録全体を表示PDF形式でダウンロード (467K) -
Yasuhiro Tanaka, Kenji Yonemitsu2008 年 77 巻 3 号 p. 034708
発行日: 2008/03/15
公開日: 2011/12/28
ジャーナル 認証ありCharge ordering with structural distortion in quasi-two-dimensional organic conductors θ-(ET)2RbZn(SCN)4 (ET = BEDT-TTF) and α-(ET)2I3 is investigated theoretically. By using the Hartree–Fock approximation for an extended Hubbard model which includes both on-site and intersite Coulomb interactions together with Peierls-type electron–lattice couplings, we examine the role of lattice degrees of freedom on charge order. It is found that the experimentally observed, horizontal charge order is stabilized by lattice distortion in both compounds. In particular, the lattice effect is crucial to the realization of the charge order in θ-(ET)2RbZn(SCN)4, while the peculiar band structure whose symmetry is lower than that of θ-(ET)2RbZn(SCN)4 in the metallic phase is also an important factor in α-(ET)2I3 together with the lattice distortion. For α-(ET)2I3, we obtain a phase transition from a charge-disproportionated metallic phase to the horizontal charge order with lattice modulations, which is consistent with the latest X-ray experimental result.抄録全体を表示PDF形式でダウンロード (238K) -
Syuma Yasuzuka, Hisashi Tanaka, Madoka Tokumoto, David Graf, Eun Sang ...2008 年 77 巻 3 号 p. 034709
発行日: 2008/03/15
公開日: 2011/12/28
ジャーナル 認証ありWe have measured the electrical resistivity and the magnetoresistance (MR) of the single-component molecular metal [Ni(tmdt)2] at high magnetic fields. The temperature dependence of the resistivity shows a T2 behavior up to 30 K, but this is difficult to explain in terms of the simple Fermi liquid picture. We find a highly isotropic positive MR below 4.2 K which exhibits a metal–insulator behavior. These results are discussed in terms of the Zeeman effect in the presence of spin–orbit coupling on the Ni sites.抄録全体を表示PDF形式でダウンロード (394K) -
Toshifumi Hara, Ko Furukawa, Toshikazu Nakamura, Yohei Yamamoto, Atsuk ...2008 年 77 巻 3 号 p. 034710
発行日: 2008/03/15
公開日: 2011/12/28
ジャーナル 認証ありESR and 1H NMR investigations were performed on iodine-doped HBC nanotubes to understand the low-temperature electronic states and carrier dynamics. Using ESR measurements, we clarified that the charged carriers induced by iodine-doping possess spins, and we found two kinds of spin species with different doping levels. The ESR results indicate the itinerant features down to 170 K. The 1H T1−1 for the heavy-iodine-doped HBC nanotubes follows T0.5 and exhibits a characteristic frequency dependence. We propose that the spin excitation propagates along the one-dimensional helical chain.抄録全体を表示PDF形式でダウンロード (1678K) -
Manabu Takahashi, Junichi Igarashi, Takuji Nomura2008 年 77 巻 3 号 p. 034711
発行日: 2008/03/15
公開日: 2011/12/28
ジャーナル 認証ありWe present a detailed analysis of the incident-photon-energy and polarization dependences of the resonant inelastic x-ray scattering (RIXS) spectra at the Cu K edge in La2CuO4. Our analysis is based on the formula developed by Nomura and Igarashi, which describes the spectra by a product of an incident-photon-dependent factor and a density–density correlation function for 3d states. We calculate the former factor using the 4p density of states from an ab-initio band structure calculation and the latter using a multiorbital tight-binding model within the Hartree–Fock approximation and the random phase approximation. We obtain spectra with rich structures in the energy-loss range 2–5 eV, which vary with varying momentum and incident-photon energy, in semi-quantitative agreement with recent experiments. We clarify the origin of such changes as a combined effect of the incident-photon-dependent factor and the density–density correlation function.抄録全体を表示PDF形式でダウンロード (626K) -
Hiroyasu Koizumi2008 年 77 巻 3 号 p. 034712
発行日: 2008/03/15
公開日: 2011/12/28
ジャーナル 認証ありWe show that spin vortex excitations in a two-dimensional half-filled antiferromagnetic insulator are accompanied by loop currents; they are the collective flow of electrons generated by a fictitious magnetic field, where the field arises from a phase factor that ensures the single-valuedness of wave functions for electron hopping motion. We study effectively half-filled states of a U>>t Hubbard model in which all holes added to the exactly half-filled antiferromagnetic insulator become self-trapped polarons. Using the perturbation theory, we demonstrate that loop currents arise when spin vortices are created and partially retrieve the itineracy of electrons in the upper Hubbard band. We also perform mean-field calculations to gain qualitative insights on the loop current state using parameters appropriate for cuprate superconductors. It is shown that a collection of loop currents creates a large current flow region or a “river” of current. A calculated ARPES profile exhibits a Fermi arc feature seen in cuprates when an extended loop current region is present; thus, it is suggested that such a current region may be the origin of the Fermi arc. The elastic neutron scattering cross section profiles are also calculated and a splitting of peaks that resembles experimental results is obtained.抄録全体を表示PDF形式でダウンロード (586K) -
Kenya Ohgushi, Yoichi Okimoto, Takeshi Ogasawara, Shigeki Miyasaka, Yo ...2008 年 77 巻 3 号 p. 034713
発行日: 2008/03/15
公開日: 2011/12/28
ジャーナル 認証ありA comprehensive study of magnetic, optical, and magnetooptical properties was carried out for single crystals of the spinel-type ACr2X4 (A=Mn, Fe, Co, Cu, Zn, and Cd; X=O, S, and Se). The optical reflectivity measurements for 0.1–30 eV revealed a wide variation in electronic structures on a large energy scale between oxides (X=O) and chalcogenides (X=S and Se). For A=Fe and Co, we observed the intra-atomic d–d transitions of A2+ ions with a tetrahedral coordination, and successfully deduced the crystal field splitting ΔE, the Racah parameter B, and the spin–orbit coupling constant ζ by analysis based on the ligand field theory. A comparison of these optical parameters between oxides and chalcogenides indicated the strong covalency effect in the chalcogenides. In A=Cu, the insulator–metal transition between X=O and Se was clearly demonstrated by optical conductivity spectra. Magnetic properties were discussed in relation to electronic structures. A compound with a small optical gap is typically a ferrimagnet with antiparallel arrangements of A2+ and Cr3+ spins, whereas a compound with a large optical gap undergoes first-order phase transition into spiral spin ordering at a low temperature. We found that the magnetic anisotropy constants K1 for ACr2S4 (A=Mn, Fe, and Co) are approximately scaled by the inverse of the intra-atomic d–d transition energies of A2+ ions in agreement with the second-order perturbation theory for single-ion anisotropy. The magnetooptical spectra in a wide energy range (0.2–4.5 eV) were measured for chalcogenides focusing on the d–d transition resonance. We observed gigantic magnetooptical signals up to 4.1° in the energy range of 4A2→4T2 and 4A2→4T1 transitions of Co2+ ions for CoCr2S4, and analyzed them in the framework of the ligand field theory. We propose that the strong covalency of the ligand sulfur, as well as the local breakdown of inversion symmetry, in the tetrahedral site plays a crucial role in the enhancement of magnetooptical responses.抄録全体を表示PDF形式でダウンロード (864K)