210 research outputs found
Magnetic structure of the field-induced multiferroic GdFe3(BO3)4
We report a magnetic x-ray scattering study of the field-induced multiferroic
GdFe3(BO3)4. Resonant x-ray magnetic scattering at the Gd LII,III edges
indicates that the Gd moments order at TN ~ 37 K. The magnetic structure is
incommensurate below TN, with the incommensurability decreasing monotonically
with decreasing temperature until a transition to a commensurate magnetic phase
is observed at T ~ 10 K. Both the Gd and Fe moments undergo a spin
reorientation transition at TSR ~ 9 K such that the moments are oriented along
the crystallographic c axis at low temperatures. With magnetic field applied
along the a axis, our measurements suggest that the field-induced polarization
phase has a commensurate magnetic structure with Gd moments rotated ~45 degrees
toward the basal plane, which is similar to the magnetic structure of the Gd
subsystem observed in zero field between 9 and 10 K, and the Fe subsystem has a
ferromagnetic component in the basal plane.Comment: 27 pages, 7 figures, to appear in Phys. Rev.
Pinning Enhancement by Heterovalent Substitution in YREBaCuO
The intragrain pinning in high- superconductor compounds
YREBaCuO with low concentration of RE
(La, Ce, Pr) was investigated. Magnetic and transport measurements reveal that
the pinning is maximal for the concentration of heterovalent RE such that the
average distance between the impurity ions in the plane of rare-earth elements
close to the diameter of Abrikosov vortices in YBCO.Comment: 11 pages, 6 figures, will be published in SUS
Conductivity, weak ferromagnetism and charge instability in single crystal
The temperature dependence of resistivity, magnetization and electron-spin
resonance of the single crystal were measured in temperature
range of . Magnetization hysteresis in applied magnetic field
up to 0.7 T at , irreversible temperature behavior of
magnetization and resistivity were found . The obtained data were explained in
terms of degenerate tight binding model using random phase approximation. The
contribution of holes in and bands of manganese ions to the
conductivity, optical absorbtion spectra and charge instability in were studied. Charge susceptibility maxima resulted from the competition of
the on-site Coulomb interaction between the holes in different orbitals and
small hybridization of sub-bands were calculated at .Comment: 6 pages, 12 figure
Anisotropy and crystallite misalignment in textured superconductors
A misalignment of anisotropic crystallites causes small values of anisotropy
and decreases the critical current density of textured polycrystalline
superconductors. To relate the crystallite misalignment and out-plane
anisotropy, the magnetic properties of the textured Bi2223 polycrystalline
superconductor were investigated. A distribution of orientation angles of
crystallites was determined using different data: scanning electron microscopy
images and hysteresis magnetization loops when an external magnetic field was
applied at different angles with respect to the texturing plane of the sample.
It was demonstrated that the standard deviation of the distribution and the
magnetic disorder angle of crystallites in textured samples can be determined
from the magnetization data in perpendicular directions. These data may be
either the irreversible magnetization measured for two different orientations
of the sample or the simultaneously measured magnetization projections parallel
and perpendicular to the magnetic field.Comment: 11 pages, 6 figure
SEARCH FOR BITARGET HDACi AND VEGFR-2 PREPARATIONS BASED ON A COMBINATION OF QUINAZOLIN-4(3H)-ONE DERIVATIVES VIA A LINKER WITH HYDROXAMIC ACID
This work was supported by the Ministry of Education and Science of the Russion Federation (Agreement № 075-11-2018-172 dated 03.12.18) Unique project identifier RFMEFI62418X0051
Raman scattering from phonons and magnons in RFe3)BO3)4
Inelastic light scattering spectra of several members of the RFe3(BO3)4
family reveal a cascade of phase transitions as a function of temperature,
starting with a structural, weakly first order, phase transition followed by
two magnetic phase transitions. Those consist of the ordering of the Fe-spin
sublattice revealed by all the compound, and a subsequent spin-reorientational
transition for GdFe3(BO3)4. The Raman data evidence a strong coupling between
the lattice and magnetic degrees of freedom in these borates. The Fe-sublattice
ordering leads to a strong suppression of the low energy magnetic scattering,
and a multiple peaked two-magnon scattering continuum is observed. Evidence for
short-range correlations is found in the `paramagnetic' phase by the
observation of a broad magnetic continuum in the Raman data, which persists up
to surprisingly high temperatures.Comment: 17 pages, 13 figure
Magnetization and specific heat of TbFe3(BO3)4: Experiment and crystal field calculations
We have studied the thermodynamic properties of single-crystalline
TbFe3(BO3)4. Magnetization measurements have been carried out as a function of
magnetic field (up to 50 T) and temperature up to 350K with the magnetic field
both parallel and perpendicular to the trigonal c-axis of the crystal. The
specific heat has been measured in the temperature range 2-300K with a magnetic
field up to 9 T applied parallel to the c-axis. The data indicate a structural
phase transition at 192 K and antiferromagnetic spin ordering at 40 K. A
Schottky anomaly is present in the specific heat data around 20 K, arising due
to two low-lying energy levels of the Tb3+ ions being split by f-d coupling.
Below TN magnetic fields parallel to the c-axis drive a spin-flop phase
transition, which is associated with a large magnetization jump. The highly
anisotropic character of the magnetic susceptibility is ascribed mainly to the
Ising-like behavior of the Tb3+ ions in the trigonal crystal field. We describe
our results in the framework of an unified approach which is based on
mean-field approximation and crystal-field calculations.Comment: 10 pages, 10 figures, 20 references, accepted by Phys. Rev.
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