3,046 research outputs found
Versatile helimagnetic phases under magnetic fields in cubic perovskite SrFeO3
A helical spin texture is of great current interest for a host of novel
spin-dependent transport phenomena. We report a rich variety of nontrivial,
helimagnetic phases in the simple cubic perovskite SrFeO3 under magnetic fields
up to 42 T. Magnetic and resistivity measurements revealed that the
proper-screw spin phase proposed for SrFeO3 can be subdivided into at least
five kinds of ordered phases. Near the multicritical point, an unconventional
anomalous Hall effect was found to show up and was interpreted as due to a
possible long-period noncoplanar spin texture with scalar spin chirality.Comment: 5 pages, 5 figures, Physical Review B in pres
Superconformal Symmetry in Linear Sigma Model on Supermanifolds
We consider a gauged linear sigma model in two dimensions with Grassmann odd chiral superfields. We investigate the Konishi anomaly of this model and find out the condition for realization of superconformal symmetry on the world-sheet. When this condition is satisfied, the theory is expected to flow into conformal theory in the infrared limit. We construct superconformal currents explicitly and study some properties of this world-sheet theory from the point of view of conformal field theories
The Effect of Platinum-coatings on Hydrogen- and Water-absorption and Desorption Characteristics of Lithium Zirconate
AbstractHydrogen (H)- and water (H2O)-storage and desorption characteristics of 25nm thick Pt films onLi2ZrO3composite materials, exposed to normal air at room temperature, have been investigated by means of elastic recoil detection (ERD), Rutherford backscattering spectrometry (RBS), weight gain measurement (WGM), and thermal desorption spectroscopy (TDS) techniques. It was found by the ERD and TDS that H and H2O were absorbed into the Pt-coated Li2ZrO3 in air at room temperature and desorbed from it in vacuum at much low temperatures of approximately 317 and 309K, respectively. In addition, the WGM and TDS spectra revealed that the absorption and desorption characters ofsome gases such as CH4, CO, and CO2including H as well as H2Ointo the Li2ZrO3 bulk were improved by Pt deposition
Anisotropic magnetic field responses of ferroelectric polarization in a trigonal multiferroic CuFe1-xAlxO2 (x=0.015)
We have investigated magnetic field dependences of a ferroelectric
incommensurate-helimagnetic order in a trigonal magneto-electric (ME)
multiferroic CuFe1-xAlxO2 with x=0.015, which exhibits the ferroelectric phase
as a ground state, by means of neutron diffraction, magnetization and
dielectric polarization measurements under magnetic fields applied along
various directions. From the present results, we have established the H-T
magnetic phase diagrams for the three principal directions of magnetic fields;
(i) parallel to the c axis, (ii) parallel to the helical axis, and (iii)
perpendicular to the c and the helical axes. While the previous dielectric
polarization (P) measurements on CuFe1-xGaxO2 with x=0.035 have demonstrated
that the magnetic field dependence of the `magnetic domain structure' results
in distinct magnetic field responses of P [S. Seki et al., Phys. Rev. Lett.,
103 237601 (2009)], the present study have revealed that the anisotropic
magnetic field dependence of the ferroelectric helimagnetic order `in each
magnetic domain' can be also a source of a variety of magnetic field responses
of P in CuFe1-xAxO2 systems (A=Al, Ga).Comment: 11 pages, 9 figures, accepted for publication in Phys. Rev.
The abundances of ethane to acetylene in the atmospheres of Jupiter and Saturn
The present determination of the stratospheric abundances of ethane and acetylene on Jupiter and Saturn on the basis of IR spectra near 780/cm uses atmospheric models whose thermal and density profiles have constant mixing ratios. The ratio of ethane to acetylene is noted to be insensitive to model atmosphere assumptions; it is 55 + or - 31 for Jupiter and 23 + or - 12 where model mixing ratios are uniform. Atmospheric model density profiles adapted from theoretical photochemical models are noted to also yield a higher ethane/acetylene ratios for Jupiter
A strong 3.4 micron emission feature in comet Austin 1989c1
High resolution 2.8-4.0 micron spectra of the 'new' comet Austin 1989c1, taken on 15-16 May 1990 confirm the presence of the broad emission features around 3.4 and 3.52 micron seen in a number of bright comets and ascribed to organic material. Both the 3.4 micron band strength and the 3.52/3.36 micron flux ratios are among the largest so far observed. The data are consistent with the relationship between band strength and water production rate that was recently derived. Excess emission at 3.28 and 3.6 micron cannot be unambiguously identified as features due to the poor signal-to-noise ratio
Nonadiabatic transitions in a Stark decelerator
In a Stark decelerator, polar molecules are slowed down and focussed by an
inhomogeneous electric field which switches between two configurations. For the
decelerator to work, it is essential that the molecules follow the changing
electric field adiabatically. When the decelerator switches from one
configuration to the other, the electric field changes in magnitude and
direction, and this can cause molecules to change state. In places where the
field is weak, the rotation of the electric field vector during the switch may
be too rapid for the molecules to maintain their orientation relative to the
field. Molecules that are at these places when the field switches may be lost
from the decelerator as they are transferred into states that are not focussed.
We calculate the probability of nonadiabatic transitions as a function of
position in the periodic decelerator structure and find that for the
decelerated group of molecules the loss is typically small, while for the
un-decelerated group of molecules the loss can be very high. This loss can be
eliminated using a bias field to ensure that the electric field magnitude is
always large enough. We demonstrate our findings by comparing the results of
experiments and simulations for the Stark deceleration of LiH and CaF
molecules. We present a simple method for calculating the transition
probabilities which can easily be applied to other molecules of interest.Comment: 12 pages, 9 figures, minor revisions following referee suggestion
A search for varying fundamental constants using Hz-level frequency measurements of cold CH molecules
Many modern theories predict that the fundamental constants depend on time,
position, or the local density of matter. We develop a spectroscopic method for
pulsed beams of cold molecules, and use it to measure the frequencies of
microwave transitions in CH with accuracy down to 3 Hz. By comparing these
frequencies with those measured from sources of CH in the Milky Way, we test
the hypothesis that fundamental constants may differ between the high and low
density environments of the Earth and the interstellar medium. For the fine
structure constant we find \Delta\alpha/\alpha = (0.3 +/- 1.1)*10^{-7}, the
strongest limit to date on such a variation of \alpha. For the
electron-to-proton mass ratio we find \Delta\mu/\mu = (-0.7 +/- 2.2) * 10^{-7}.
We suggest how dedicated astrophysical measurements can improve these
constraints further and can also constrain temporal variation of the constants.Comment: 8 pages, 3 figure
- …