L. N. Bezmaternykh

Magnetoelectric effects in gadolinium iron borate GdFe3(BO3)4

Magnetoelectric interactions have been investigated in a single crystal of gadolinium iron borate GdFe3(BO3)4, whose macroscopic symmetry is characterized by the crystal class 32. Using the results of this study, the interplay of magnetic and electric orderings occurring in the system has been experimentally revealed and theoretically substantiated. The electric polarization and magnetostriction of this material that arise in spin-reorientation transitions induced by a magnetic field have been investigated experimentally. For H ‖ c and H ⊥ c, H-T phase diagrams have been constructed, and a strict correlation between the changes in the magnetoelectric and magnetoelastic properties in the observed phase transitions has been ascertained. A mechanism of specific noncollinear antiferroelectric ordering at the structural phase transition point was proposed to interpret the magnetoelectric behavior of the system within the framework of the symmetry approach in the entire temperature range. This ordering provides the conservation of the crystal class of the system when the temperature decreases to the antiferroelectric ordering point. The expressions that have been obtained for the magnetoelectric and magnetoelastic energy describe reasonably well the behavior of gadolinium iron borate observed experimentally.

Magnetoelectric and magnetoelastic properties of rare-earth ferroborates

The magnetic, electric, magnetoelectric, and magnetoelastic properties of rare-earth ferroborates RFe3(BO3)4 (R=Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er) as well as yttrium ferroborate YFe3(BO3)4 have been studied comprehensively. A strong dependence not only of the magnetic but also magnetoelectric properties on the type of rare-earth ion, specifically, on its anisotropy, which determines the magnetic structure and the large contribution to the electric polarization, has been found. This is manifested in the strong temperature dependence of the polarization below the Neel point TN and its specific field dependence, which is determined by the competition between the external and exchange f-d fields. A close correlation has been found between the magnetoelastic properties of ferroborates and the magnetoelastic and magnetic anomalies at magnetic-field induced phase transitions. It is found that in easy-plane ferroborates, together with magnetic-field induced electric polarization spontaneous polarization also ari...

Magnetoelectric and magnetoelastic interactions in NdFe3(BO3)4 multiferroics

Complex experimental and theoretical investigations of the magnetic, magnetoelectric, and magnetoelastic properties of neodymium iron borate NdFe3(BO3)4 along various crystallographic directions have been carried out in strong pulsed magnetic fields up to 230 kOe in a temperature range of 4.2–50 K. It has been found that neodymium iron borate, as well as gadolinium iron borate, is a multiferroic. It has a much larger (above 300 μC/m2) electric polarization controlled by the magnetic field and giant quadratic magnetoelectric effect. The exchange field between the rare-earth and iron subsystems (∼50 kOe) has been determined for the first time from experimental data. The theoretical analysis based on the magnetic symmetry and quantum properties of the Nd ion in the crystal provides an explanation of the unusual behavior of the magnetoelectric and magnetoelastic properties of neodymium iron borate in strong magnetic fields and correlation observed between them.

Evidence for differentiation in the iron-helicoidal chain in GdFe3(BO3)4.

A single-crystal X-ray structure study of gadolinium triiron tetraborate, GdFe3(BO3)4, at room temperature and at 90 K is reported. At room temperature GdFe3(BO3)4 crystallizes in a trigonal space group, R32 (No. 155), the same as found for other members of the iron borate family RFe3(BO3)4. At 90 K the structure of GdFe3(BO3)4 transforms to the space group P3(1)21 (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 presence of two inequivalent iron chains in the low-temperature structure provides a new perspective on the interpretation of the low-temperature magnetic properties.

Crystallization of trigonal (Tb,Er)(Fe,Ga)3(BO3)4 phases with hantite structure in bismuth trimolybdate-based fluxes

The stability regions of the trigonal (Tb,Er)(Fe,Ga)3(BO3)4 phases are established in (Bi2Mo3O12)-based fluxes. The specific features of heterogeneous nucleation and the subsequent phase transformations during transition to the equilibrium are studied in the vicinity of the boundaries. The temperature modes of single crystal growth on seeds are suggested with due regard for the “nonequilibrium effect.”

Optical spectra, crystal-field parameters, and magnetic susceptibility of multiferroic Nd Fe 3 ( B O 3 ) 4

We report high-resolution optical absorption spectra for

Magnetization and specific heat of TbFe3"BO3…4: Experiment and crystal-field calculations

\mathrm{Nd}{\mathrm{Fe}}_{3}{(\mathrm{B}{\mathrm{O}}_{3})}_{4}

Giant magnetoelectric effect in HoAl3(BO3)4

trigonal single crystal, which is known to exhibit a giant magnetoelectric effect below the temperature of magnetic ordering

Colossal magnetodielectric effect in SmFe3(BO3)4 multiferroic

{T}_{N}=33\phantom{\rule{0.3em}{0ex}}\mathrm{K}

Cascade of phase transitions in GdFe3(BO3)4

. The analysis of the temperature-dependent polarized spectra reveals the energies and, in some cases, symmetries and exchange splittings of