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.

The influence of the industrial complex on the atmospheric air in the Sverdlovsk region

The work is dedicated to studying the level dynamics of polluting substances emissions into the atmosphere of Yekaterinburg city and the Sverdlovsk region in the period of 2012-2016. In the process of our work we found out an insignificant reduction of main indicators values such as SI, HR, and IPA to estimate the atmospheric air quality. Nevertheless, the level of the air pollution in Yekaterinburg city remained high in the stated period. We also suggested some methods to reduce enterprises emissions in the article, which will lead to improving the air quality. In the result of our work it was established that the main pollutants are suspended particles, nitrogen dioxides, phenol, and benzene. Moreover, the connection between the atmospheric air pollution degree and the Sverdlovsk region population's health was determined. © 2018 Institute of Physics Publishing. All rights reserved

Evidence for differentiation in the iron-helicoidal-chain in GdFe3_{3}(BO3_{3})4_{4}

We report on a single-crystal X-ray structure study of $GdFe_{3}(BO_{3})_{4}$ at room temperature and at T=90 K. At room temperature $GdFe_{3}(BO_{3})_{4}$ crystallizes in a trigonal space group R32 (No. 155), the same as found for other members of iron-borate family $RFe_{3}(BO_{3})_{4}$. At 90 K the structure of $GdFe_{3}(BO_{3})_{4}$ has transformed to the space group $P3_{1}2_{1}$ (No. 152). The low-temperature structure determination gives new insight into the weakly first-order structural phase transition at 156 K and into the related Raman phonon anomalies. The discovery of two inequivalent iron chains in the low temperature structure provide new point of view on the low-temperature magnetic properties.Comment: Subm. to Acta Cryst.

Optical spectra, crystal-field parameters, and magnetic susceptibility of the new multiferroic NdFe3(BO3)4

We report high-resolution optical absorption spectra for NdFe3(BO3)4 trigonal single crystal which is known to exhibit a giant magnetoelectric effect below the temperature of magnetic ordering TN = 33 K. The analysis of the temperature-dependent polarized spectra reveals the energies and, in some cases, symmetries and exchange splittings of Nd3+ 84 Kramers doublets. We perform crystal-field calculations starting from the exchange-charge model, obtain a set of six real crystal-field parameters, and calculate wave functions and magnetic g-factors. In particular, the values g(perpendicular) = 2.385, g(parallel) = 1.376 were found for the Nd3+ ground-state doublet. We obtain Bloc=7.88 T and |JFN|= 0.48 K for the values of the local effective magnetic field at liquid helium temperatures at the Nd3+ site and the Nd - Fe exchange integral, respectively, using the experimentally measured Nd3+ ground-state splitting of 8.8 cm-1. To check reliability of our set of crystal field parameters we model the magnetic susceptibility data from literature. A dimer containing two nearest-neighbor iron ions in the spiral chain is considered to partly account for quasi-one-dimensional properties of iron borates, and then the mean-field approximation is used. The results of calculations with the exchange parameters for Fe3+ ions Jnn = -6.25 K (intra-chain interactions) and Jnnn = -1.92 K (inter-chain interactions) obtained from fitting agree well with the experimental data.Comment: 13 pages, 8 figures, 2 table