1,130 research outputs found
Ferroelectricity induced by spin-dependent metal-ligand hybridization in BaCoGeO
We have investigated the variation of induced ferroelectric polarization
under magnetic field with various directions and magnitudes in a staggered
antiferromagnet BaCoGeO. While the ferroelectric polarization
cannot be explained by the well-accepted spin current model nor exchange
striction mechanism, we have shown that it is induced by the spin-dependent
- hybridization between the transition-metal (Co) and ligand (O) via the
spin-orbit interaction. On the basis of the correspondence between the
direction of electric polarization and the magnetic state, we have also
demonstrated the electrical control of the magnetization direction.Comment: 4 pages, 4 figure
A Web-Based VOD Clipping Tool for Efficient Private Review
In this paper, we present a web-based tool for learners, to review the parts of the lecture contents that the learners have already attended. Each learner can efficiently review what they want to learn again independent of the scenario in each lecture. We assume that the contents of the lectures are stored in the internet based video streaming systems. The objects are automatically arranged on a screen of this tool, so that each object gets closer to its similar objects.ArticleKnowledge-based software engineering : proceedings of the fifth Joint Conference on Knowledge-Based Software Engineering. 313-316 (2002)conference pape
Field-Induced Effects of Anisotropic Magnetic Interactions in SrCu2(BO3)2
We observed a field-induced staggered magnetization in the 2D frustrated
dimer-singlet spin system SrCu2(BO3)2 by 11B NMR, from which the magnitudes of
the intradimer Dzyaloshinsky-Moriya interaction and the staggered g-tensor were
determined. These anisotropic interactions cause singlet-triplet mixing and
eliminate a quantum phase transition at the expected critical field Hc for gap
closing. They also provide a quantitative account for some puzzling phenomena
such as the onset of a uniform magnetization below the and the persistence of
the excitation gap above Hc. The gap was accurately determined from the
activation energy of the nuclear relaxation rate.Comment: 8 pages, 5 figures, published versio
Electromagnons in the multiferroic state of perovskite manganites with symmetric-exchange striction
We have investigated electrically-active magnetic excitations
(electromagnons) in perovskite manganites with the -type (up-up-down-down)
spin structure by terahertz spectroscopy. EuYMnO (0.11) and YLuMnO (01) without magnetic -moments,
which host collinear sinusoidal, -type, cycloidal, and -type spin orders,
are used to examine the systematics of possible electromagnons. Three-peak
structures (23, 35, 45 cm) of magnetic origin show up in the -type
phase with little composition () dependence of frequencies, making a
contrast with the electromagnons observed in the cycloidal-spin ()
phases. One of these electromagnon is ascribed to the zone-edge magnon mode
based on the calculated magnon dispersions.Comment: 5 pages, 4 figure
Electromagnons in the multiferroic state of perovskite manganites with symmetric-exchange striction
We have investigated electrically-active magnetic excitations
(electromagnons) in perovskite manganites with the -type (up-up-down-down)
spin structure by terahertz spectroscopy. EuYMnO (0.11) and YLuMnO (01) without magnetic -moments,
which host collinear sinusoidal, -type, cycloidal, and -type spin orders,
are used to examine the systematics of possible electromagnons. Three-peak
structures (23, 35, 45 cm) of magnetic origin show up in the -type
phase with little composition () dependence of frequencies, making a
contrast with the electromagnons observed in the cycloidal-spin ()
phases. One of these electromagnon is ascribed to the zone-edge magnon mode
based on the calculated magnon dispersions.Comment: 5 pages, 4 figure
The climatology, propagation and excitation of ultra-fast Kelvin waves as observed by meteor radar, Aura MLS, TRMM and in the Kyushu-GCM
Wind measurements from a meteor radar on Ascension Island (8&deg; S, 14&deg; W) and simultaneous temperature measurements from the Aura MLS instrument are used to characterise ultra-fast Kelvin waves (UFKW) of zonal wavenumber 1 (E1) in the mesosphere and lower thermosphere (MLT) in the years 2005–2010. These observations are compared with some predictions of the Kyushu-general circulation model. Good agreement is found between observations of the UFKW in the winds and temperatures, and also with the properties of the waves in the Kyushu-GCM. UFKW are found at periods between 2.5–4.5 days with amplitudes of up to 40 m s<sup>−1</sup> in the zonal winds and 6 K in the temperatures. The average vertical wavelength is found to be 44 km. Amplitudes vary with latitude in a Gaussian manner with the maxima centred over the equator. Dissipation of the waves results in monthly-mean eastward accelerations of 0.2–0.9 m s<sup>−1</sup> day<sup>−1</sup> at heights around 95 km, with 5-day mean peak values of 4 m s<sup>−1</sup> day<sup>−1</sup>. Largest wave amplitudes and variances are observed over Indonesia and central Africa and may be a result of very strong moist convective heating over those regions. Rainfall data from TRMM are used as a proxy for latent-heat release in an investigation of the excitation of these waves. No strong correlation is found between the occurrence of large-amplitude mesospheric UFKW events and either the magnitude of the equatorial rainfall or the amplitudes of E1 signatures in the rainfall time series, indicating that either other sources or the propagation environment are more important in determining the amplitude of UFKW in the MLT. A strong semiannual variation in wave amplitudes is observed. Intraseasonal oscillations (ISOs) with periods 25–60 days are evident in the zonal background winds, zonal-mean temperature, UFKW amplitudes, UFKW accelerations and the rainfall rate. This suggests that UFKW play a role in carrying the signature of tropospheric ISOs to the MLT region
Orbital Ordering in ferromagnetic Lu2V2O7
We have observed the orbital ordering in the ferromagnetic Mott-insulator
Lu2V2O7 by the polarized neutron diffraction technique. The orbital ordering
pattern determined from the observed magnetic form factors can be explained in
terms of a linear combination of wave functions |yz>, |zx> and |xy>; |0> =
(1/3)^(1/2) |xy> + (1/3)^(1/2)|yz> + (1/3)^(1/2) |zx> which is proportional to
|(x + y + z)^2 - r^2>; where each orbital is extended toward the center-of-mass
of the V tetrahedron. We discuss the stability of the ferromagnetic Lu2V2O7,
using a Hubbard Hamiltonian with these three orbitals.Comment: 17pages. to be published in J. Phys. Soc. Jpn. 74 (2005
Hole Dynamics in the Orthogonal-Dimer Spin System
The dynamics of a doped hole in the orthogonal-dimer spin system is
investigated systematically in one, two and three dimensions. By combining the
bond-operator method with the self-consistent
Born approximation, we argue that a dispersive quasi-particle state in the
dimer phase is well defined even for quasi-two-dimensional systems. On the
other hand, a doped hole in the plaquette-singlet phase hardly itinerates,
forming an almost localized mode. We further clarify that although the
quasi-particle weight in the dimer phase is decreased in the presence of the
interchain coupling, it is not suppressed but even enhanced upon the
introduction of the interlayer coupling.Comment: 8 pages, 10 figure
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