554 research outputs found
Theory of electromagnon in the multiferroic Mn perovskites: Vital role of higher harmonic components of the spiral spin order
We study theoretically the electromagnon and its optical spectrum (OS) of the
terahertz-frequency regime in the magnetic-spiral-induced multiferroic phases
of the rare-earth (R) Mn perovskites, RMnO3, taking into account the elliptical
deformation or the higher harmonics of the spiral spin configuration, which has
been missed so far. A realistic spin Hamiltonian, which gives phase diagrams in
agreement with experiments, resolves a long standing puzzle, i.e., the
double-peak structure of the OS with a larger low-energy peak originating from
magnon modes hybridized with the zone-edge state. We also predict the magnon
branches associated with the electromagnon, which can be tested by
neutron-scattering experiment.Comment: 5 pages, 4 figure
Effect of ferroelectric layers on the magnetocapacitance properties of superlattices-based oxide multiferroics
A series of superlattices composed of ferromagnetic
LaCaMnO (LCMO) and ferroelectric/paraelectric
BaSrTiO (0x1) were deposited on SrTiO
substrates using the pulsed laser deposition. Films of epitaxial nature
comprised of spherical mounds having uniform size are obtained.
Magnetotransport properties of the films reveal a ferromagnetic Curie
temperature in the range of 145-158 K and negative magnetoresistance as high as
30%, depending on the type of ferroelectric layers employed for their growth
(\QTR{it}{i.e.} '\QTR{it}{x'} value). Ferroelectricity at temperatures ranging
from 55 K to 105 K is also observed, depending on the barium content. More
importantly, the multiferroic nature of the film is determined by the
appearance of negative magnetocapacitance, which was found to be maximum around
the ferroelectric transition temperature (3% per \QTR{it}{tesla}). These
results are understood based on the role of the ferroelectric/paraelectric
layers and strains in inducing the multiferroism.Comment: Accepted to Applied Physics Letter
Microscopic Model and Phase Diagrams of the Multiferroic Perovskite Manganites
Orthorhombically distorted perovskite manganites, RMnO3 with R being a
trivalent rare-earth ion, exhibit a variety of magnetic and electric phases
including multiferroic (i.e. concurrently magnetic and ferroelectric) phases
and fascinating magnetoelectric phenomena. We theoretically study the phase
diagram of RMnO3 by constructing a microscopic spin model, which includes not
only the superexchange interaction but also the single-ion anisotropy (SIA) and
the Dzyaloshinsky-Moriya interaction (DMI). Analysis of this model using the
Monte-Carlo method reproduces the experimental phase diagrams as functions of
the R-ion radius, which contain two different multiferroic states, i.e. the
ab-plane spin cycloid with ferroelectric polarization P//a and the bc-plane
spin cycloid with P//c. The orthorhombic lattice distortion or the
second-neighbor spin exchanges enhanced by this distortion exquisitely controls
the keen competition between these two phases through tuning the SIA and DMI
energies. This leads to a lattice-distortion-induced reorientation of P from a
to c in agreement with the experiments. We also discuss spin structures in the
A-type antiferromagnetic state, those in the cycloidal spin states, origin and
nature of the sinusoidal collinear spin state, and many other issues.Comment: 23 pages, 19 figures. Recalculated results after correcting errors in
the assignment of Dzyaloshinsky-Moriya vector
DETERMINATION OF THE INOCULATION FREQUENCY, TIMING OF INOCULATION AND DOSE OF A BACTERIAL RUMINAL INOCULANT FOR ACIDOSIS PREVENTION IN FEEDLOT CATTLE
We are evaluating the efficacy of a ruminal bacterial inoculant (Megasphaera elsdenii 407 A) for prevention of acute acidosis in grain-fed cattle. As a part of this process, we examined the effects of inoculation frequency, timing of inoculation and dose of 407 A for prevention of acute acidosis in ruminally fistulated cattle. Three levels of frequency, two levels of timing and three doses were considered, however, a complete 3x2x3 factorial study was not run because of resource constraints. The study was conducted in two separate trials. The first was designed as a 3x2 factorial experiment with inoculation frequency and timing of inoculation while holding dose constant. The second trial was designed as a 2x3 factorial experiment involving inoculation frequency and 407 A dose while holding timing constant. Both of these trials were conducted as complete block designs with seven blocks, with repeated measurements of ruminal lactic acid made across the duration of the two trials. Changes in ruminal pH for acutely acidotic cattle (pH:≤;5.0) are known to be driven largely by changes in total ruminal lactic acid concentration and that is why this variable was selected for these trials. Area under the lactic acid curves was selected as a method of summarizing across the repeated measures. Response surface techniques were used to determine the optimal settings for the treatment factors examined. Alternative designs will be contrasted
Solubility, Activity Coefficients and the Separation Factor of U/Pr Couple in Ga-In Alloys of Different Compositions in Fused LiCl-KCl-CsCl Eutectic
The equilibrium potentials of Pr3+/Pr couple, triple Pr-Ga-In and U-Ga-In alloys vs Cl-/Cl2 reference electrode at the temperature range 723-1073 K in fused LiCl-KCl-CsCl eutectic were carried out by open-circuit potentiometry. The principle thermodynamic properties, solubility and the activity coefficients of praseodymium in gallium-indium alloys, containing 20, 40 and 70 wt% indium were determined. It was established a strong interaction between atoms of Pr and liquid alloys. The temperature dependences of the separation factor of U/Pr couple vs the composition of gallium-indium alloys were calculated. © 2020 The Electrochemical Society ("ECS"). Published on behalf of ECS by IOP Publishing Limited
Observation of nuclei with energies 8-30 MeV per nucleon in the Earth's magnetosphere at the altitudes 350 KM
Observations of the flux of nuclei with an energy of IO MeV per nucleon on the Salyut-7 Station in September 1984 are presented. The observed flux is smaller by a factor of 50 than the flux detected in May, 1981
Pressure induced enhancement of ferroelectricity in multiferroic MnO(=Tb,Dy, and Ho)
Measurements of ferroelectric polarization and dielectric constant were done
on MnO (=Tb, Dy, and Ho) with applied hydrostatic pressures of up
to 18 kbar. At ambient pressure, distinctive anomalies were observed in the
temperature profile of both physical properties at critical temperatures
marking the onset of long range AFM order (T), ferroelectricity
(T) as well as at temperatures when anomalous changes in the
polarization, dielectric constant and spin wave commensurability have been
previously reported. In particular, the step in the dielectric constant at low
temperatures (T), associated with both a drop in the ferroelectric
polarization and an incommensurate magnetic structure, was shown to be suddenly
quenched upon passing an -dependent critical pressure. This was shown to
correlate with the stabilization of the high ferroelectric polarization state
which is coincident with the commensurate magnetic structure. The observation
is suggested to be due to a pressure induced phase transition into a
commensurate magnetic structure as exemplified by the pressure-temperature
(-) phase diagrams constructed in this work. The - phase diagrams
are determined for all three compounds.Comment: 8 pages, 6 figures, submitted for review in Phys. Rev.
Electrically driven spin excitation in a ferroelectric magnet DyMnO_3
Temperature (5--250 K) and magnetic field (0--70 kOe) variations of the
low-energy (1--10 meV) electrodynamics of spin excitations have been
investigated for a complete set of light-polarization configurations for a
ferroelectric magnet DyMnO by using terahertz time-domain spectroscopy. We
identify the pronounced absorption continuum (1--8 meV) with a peak feature
around 2 meV, which is electric-dipole active only for the light -vector
along the a-axis. This absorption band grows in intensity with lowering
temperature from the spin-collinear paraelectric phase above the ferroelectric
transition, but is independent of the orientation of spiral spin plane ( or
), as shown on the original (ferroelectric polarization)
phase as well as the magnetic field induced phase. The possible origin of this electric-dipole active band is argued in
terms of the large fluctuations of spins and spin-current.Comment: New version, 11 pages including colored 8 figure
Co-expression of functional human Heme Oxygenase 1, Ecto-5'-Nucleotidase and ecto-nucleoside triphosphate diphosphohydrolase-1 by "self-cleaving" 2A peptide system
We developed an F2A-based multicistronic system to evaluate functional effects of co-expression of three proteins important for xenotransplantation: heme oxygenase 1 (HO1), ecto-5'-nucleotidase (E5NT) and ecto-nucleoside triphosphate diphosphohydrolase-1 (ENTPD1). The tricistronic p2A plasmid that we constructed was able to efficiently drive concurrent expression of HO1, E5NT and ENTPD1 in HEK293T cells. All three overexpressed proteins possessed relevant enzymatic activities, while addition of furin site interfered with protein expression and activity. We conclude that our tricistronic p2A construct is effective and optimal to test the combined protective effects of HO1, E5NT and ENTPD1 against xeno-rejection mechanisms
Effects of ac-field amplitude on the dielectric susceptibility of relaxors
The thermally activated flips of the local spontaneous polarization in
relaxors were simulated to investigate the effects of the applied-ac-field
amplitude on the dielectric susceptibility. It was observed that the
susceptibility increases with increasing the amplitude at low temperatures. At
high temperatures, the susceptibility experiences a plateau and then drops. The
maximum in the temperature dependence of susceptibility shifts to lower
temperatures when the amplitude increases. A similarity was found between the
effects of the amplitude and frequency on the susceptibility.Comment: 8 pages, 7 figures, Phys. Rev. B (in July 1st
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