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 Y1−x_{1-x}REx_{x}Ba2_{2}Cu3_{3}O7−δ_{7-\delta}

The intragrain pinning in high-$T_c$ superconductor compounds Y$_{1-x}$RE$_{x}$Ba$_{2}$Cu$_{3}$O$_{7-\delta}$ 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

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

Conductivity, weak ferromagnetism and charge instability in α−MnS\alpha-MnS single crystal

The temperature dependence of resistivity, magnetization and electron-spin resonance of the $\alpha- MnS$ single crystal were measured in temperature range of $5 K < T < 550 K$. Magnetization hysteresis in applied magnetic field up to 0.7 T at $T=5 K, 77 K, 300 K$, 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 $t_{2g}$ and $e_g$ bands of manganese ions to the conductivity, optical absorbtion spectra and charge instability in $\alpha -MnS$ 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 $T=160 K, 250 K, 475 K$.Comment: 6 pages, 12 figure

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

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

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.