Comparing the magnetic and magnetoelectric properties of the SmFe3(BO3)4 ferroborate single crystals grown using different solvents

SmFe3(BO3)4 single crystals have been grown from the bismuth trimolybdate and lithium tungstate-based melt–solutions. Samarium ferroborate single crystals were grown first from the lithium–tungstate flux. The magnetic and magnetoelectric properties of the synthesized crystals have been compared. It is shown that the SmFe3(BO3)4 ferroborate grown from the bismuth trimolybdate-based melt–solution contains impurities of Bi3+ ions (∼5% at.), which replace Sm3+ ions, while the SmFe3(BO3)4, ferroborate grown from the lithium tungstatebased melt–solution contains minor or zero amounts of such impurities. The magnetoelectric and magnetodielectric effects with the Bi3+ admixture appeared 1.5× stronger than in SmFe3(BO3)4; this is probably due to twinning

Magnetic properties of Ho0.9Er0.1Fe3(BO3)4

The magnetic properties of Ho0.9Er0.1Fe3(BO3)4 ferroborate with the competing Ho– Fe and Er–Fe exchange couplings have been experimentally and theoretically investigated. The measured magnetic characteristics (Mа,с(В), χа,с(T)) and observed features are interpreted using a single theoretical approach based on the molecular-field approximation and calculations within the crystal-field model of the rare-earth ion. Interpretation of the experimental data includes determination of the crystal-field parameters for Ho3+ and Er3+ ions in Ho0.9Er0.1Fe3(BO3)4 and parameters of the Ho–Fe and Er–Fe exchange couplings

Crystal Structure Dynamics of RFe3(BO3)4 Single Crystals in the Temperature Range 25–500 K

The multiferroic RFe3(BO3)4 family is characterized by diverse magnetic, magnetoelectric, and magnetoelastic properties, the fundamental aspects of which are essential for modern electronics. The present research, using single-crystal X-ray diffraction (XRD) and Mössbauer spectroscopy (MS) in the temperature range of 25–500 K, aimed to analyze the influence of local atomic coordination on magnetoelectric properties and exchange and super-exchange interactions in RFe3(BO3)4. Low-temperature, single-crystal XRD data of the magnetically ordered phase of RFe3(BO3)4 at 25 K, which were obtained for the first time, were supplemented with data obtained at higher temperatures, making it possible to draw conclusions about the mechanism of the structural dynamics. It was shown that, in structures with R = Gd, Ho, and Y (low-temperature space group P3121), a shift in oxygen atoms (O2, second coordination sphere of R atoms) was accompanied by rotation of the B2O3 triangle toward R atoms at low temperatures, and by different rearrangements in iron chains of two types, in contrast to Nd and Sm iron borates (space group R32). These rearrangements in the structures of space group P3121 affected the exchange and super-exchange paths at low temperatures. The MS results confirm the influence of the distant environment of atoms on the magnetoelectric properties of rare-earth iron borates at low temperatures

Pressure–Temperature Phase Diagram of Multiferroic TbFe2.46Ga0.54(BO3)4

The pressure–temperature phase diagram of the multiferroic TbFe2.46Ga0.54(BO3)4 was studied for hydrostatic pressures up to 7 GPa and simultaneously with temperatures up to 400 K by the Raman spectroscopy technique. The structural phase transition from the R32 phase to the P3121 phase was determined by observing the condensation of soft modes and the appearance of new lines. An increase in pressure leads to an increase in the temperature of the structural phase transition. These phases are stable over the entire investigated temperature and pressure range. No other phases have been found

Gallium Composition-Dependent Structural Phase Transitions in HoFe3–xGax(BO3)4 Solid Solutions: Crystal Growth, Structure, and Raman Spectroscopy Study

Текст статьи не публикуется в открытом доступе в соответствии с политикой журнала.Single crystals of solid solutions of HoFe3–xGax(BO3)4 with x = 0, 0.5, 1, 1.5, and 3 were obtained using flux synthesis. The conditions of the synthesis are described in detail. The structural properties of each of the synthesized samples were studied using X-ray powder diffraction analysis at several temperature points (303, 403, and 503 K). The structural parameters of the obtained samples and the “pure” compounds HoFe3(BO3)4 and HoGa3(BO3)4 were compared. The Raman spectra of the obtained solid solutions HoFe3–xGax(BO3)4 were studied in a wide temperature range (T = 10–400 K). The vibrational spectra and eigenvectors of the HoFe3Ga(BO3)4 and HoGa3(BO3)4 in R32 phase and HoFe3Ga(BO3)4 in P3121 phase were calculated within density functional theory. The features of the Raman spectra of HoFe2Ga(BO3)4, HoFe2.5Ga0.5(BO3)4, HoFe3(BO3)4 crystals associated with the R32 → P3121 structural phase transition, which have a strong dependence on the degree of substitution x, were investigated. Peculiarities of the Raman spectra, which are associated with magnetic ordering in HoFe1.5Ga1.5(BO3)4, HoFe2Ga(BO3)4, and HoFe2.5Ga0.5(BO3)4 crystals, were detected

Crystal Growth and Raman Spectroscopy Study of Sm_1–<i>x</i>La_<i>x</i>Fe₃(BO₃)₄ Ferroborates

Sm_1–<i>x</i>La_<i>x</i>Fe₃(BO₃)₄ (<i>x</i> = 0, 0.75) single crystals were synthesized using the flux method. The crystal nucleation procedure and flux parameters are reported. Conditions for growing the Sm_1–<i>x</i>La_<i>x</i>Fe₃(BO₃)₄ (<i>x</i> = 0, 0.75) single crystals are described. The prepared crystals were studied by Raman spectroscopy in the temperature range of <i>T</i> = 10–300 K. The spectral region corresponding to temperatures of <i>T</i> = 10–55 K, which involves the temperatures of the magnetic phase transition <i>T</i>_N = 32 K for <i>x</i> = 0 and <i>T</i>_N = 31 K for <i>x</i> = 0.75, was thoroughly analyzed. Anomalies related to the magnetic ordering established in both compounds were found. The main changes occur in the low-wavenumber region (up to 100 cm^–1), where the mode corresponding to magnon scattering arises. This mode is shown to have the internal structure indicative of the occurrence of unstable vibrations (40–80 cm^–1). The results obtained are analyzed by calculating the empirical lattice dynamics in Sm_1–<i>x</i>La_<i>x</i>Fe₃(BO₃)₄ with <i>x</i> = 0 and <i>x</i> = 1

Crystal Structure Dynamics of RFe₃(BO₃)₄ Single Crystals in the Temperature Range 25–500 K

The multiferroic RFe3(BO3)4 family is characterized by diverse magnetic, magnetoelectric, and magnetoelastic properties, the fundamental aspects of which are essential for modern electronics. The present research, using single-crystal X-ray diffraction (XRD) and Mössbauer spectroscopy (MS) in the temperature range of 25–500 K, aimed to analyze the influence of local atomic coordination on magnetoelectric properties and exchange and super-exchange interactions in RFe3(BO3)4. Low-temperature, single-crystal XRD data of the magnetically ordered phase of RFe3(BO3)4 at 25 K, which were obtained for the first time, were supplemented with data obtained at higher temperatures, making it possible to draw conclusions about the mechanism of the structural dynamics. It was shown that, in structures with R = Gd, Ho, and Y (low-temperature space group P3121), a shift in oxygen atoms (O2, second coordination sphere of R atoms) was accompanied by rotation of the B2O3 triangle toward R atoms at low temperatures, and by different rearrangements in iron chains of two types, in contrast to Nd and Sm iron borates (space group R32). These rearrangements in the structures of space group P3121 affected the exchange and super-exchange paths at low temperatures. The MS results confirm the influence of the distant environment of atoms on the magnetoelectric properties of rare-earth iron borates at low temperatures

Synthesis of NdSc3(BO3)4 single crystals and study of its structure properties

Using the group method, single crystals of NdSc3(BO3)4 are grown from a melt solution and X-ray structural studies are performed. It is shown that at room temperature the NdSc3(BO3)4 crystal has a huntite-type structure with space group P3121. The temperature dependence of the heat capacity shows anomalous behaviour at Т ¼ 504 ± 1 K. This anomaly corresponds to a structural phase transition from R32 to P3121. It is known that a similar transition occurs in RFe3(BO3)4 crystals; an anomaly in the specific heat is also observed. Theoretical calculations are carried out from the first principles of the lattice dynamics of the crystal under study in a high-symmetry phase with the R32 space group. An unstable (soft) mode in the boundary point of Brillouin zone was found. It was determined that this structural instability is responsible for the structural displacement-type phase transition R32 / P3121

Manganese Luminescent Centers of Different Valence in Yttrium Aluminum Borate Crystals

We present an extensive study of the luminescence characteristics of Mn impurity ions in a YAl3(BO3)4:Mn crystal, in combination with X-ray fluorescence analysis and determination of the valence state of Mn by XANES (X-ray absorption near-edge structure) spectroscopy. The valences of manganese Mn2+(d5) and Mn3+(d4) were determined by the XANES and high-resolution optical spectroscopy methods shown to be complementary. We observe the R1 and R2 luminescence and absorption lines characteristic of the 2E ↔ 4A2 transitions in d3 ions (such as Mn4+ and Cr3+) and show that they arise due to uncontrolled admixture of Cr3+ ions. A broad luminescent band in the green part of the spectrum is attributed to transitions in Mn2+. Narrow zero-phonon infrared luminescence lines near 1060 nm (9400 cm−1) and 760 nm (13,160 cm−1) are associated with spin-forbidden transitions in Mn3+: 1T2 → 3T1 (between excited triplets) and 1T2 → 5E (to the ground state). Spin-allowed 5T2 → 5E Mn3+ transitions show up as a broad band in the orange region of the spectrum. Using the data of optical spectroscopy and Tanabe–Sugano diagrams we estimated the crystal-field parameter Dq and Racah parameter B for Mn3+ in YAB:Mn as Dq = 1785 cm−1 and B = 800 cm−1. Our work can serve as a basis for further study of YAB:Mn for the purposes of luminescent thermometry, as well as other applications