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The authors study the formation of crystals of Fe-Ga oxides and Fe–Ga–Cu borates in a multicomponent flux system based on Bi2Mo3O12–Na2B4O7. The Curie–Weiss temperature (θCW = 289 K) and the temperature of the ferrimagnet–paramagnet phase transition (TC = 288 K) are determined from the electron spin resonance (ESR) spectrum and the magnetization of an Fe1.1Ga0.9O3 single crystal, depending on temperature. Lines of spin-wave resonance are observed in the spectrum of magnetic resonance in the ordered phase. [ABSTRACT FROM AUTHOR]

Results are presented from investigating the structure of Mn2.25Co0.75BO5 via powder neutron diffraction. Crystals of ludwigite Mn2.25Co0.75BO5 are grown by flux method using a Bi2Mo3O12-based solvent diluted with Na2CO3 carbonate. Boric acid is used as the boron-containing reagent. Powder neutron diffraction measurements are made at a temperature of 100 K on powder prepared by grinding grown single crystals. Rietveld studies show that the grown Mn2.25Co0.75BO5 crystals belong to Pbam space group. Crystallographic sites occupied by cobalt and manganese ions are identified by analyzing powder neutron diffractograms. A bottleneck regime is observed in the temperature dependence of the EPR spectra. [ABSTRACT FROM AUTHOR]

Copper oxyborate single crystals with a ludwigite structure, Cu2MBO5 (M = Cr, Fe, Mn), containing different substitutes in the trivalent subsystem have been grown from Bi2O3–MoO3–Na2O–B2O3 fluxes. The structural properties of grown compounds have been compared in detail using X-ray diffraction and Raman spectroscopy methods. In addition, these methods have been used to determine the degree of cationic ordering in these ludwigites. The temperature and field dependences of the Cu2MBO5 (M = Cr, Fe, Mn) ludwigite magnetization are presented. [ABSTRACT FROM AUTHOR]

Cobalt pyroborate Co2B2O5 single crystals have been obtained by spontaneous crystallization from solution–melt. Powder X-ray diffraction measurements have revealed the triclinic symmetry with the lattice parameters Å, Å, Å, , , , and Å3. Magnetic properties have been studied in the temperature range of 4.2–300 K and in magnetic fields up to 90 kOe by measuring the static magnetization and molar heat capacity. A transition to an antiferromagnetic state has been detected at TN = 45 K. A spin-flop transition occurs in the sample in strong magnetic fields. [ABSTRACT FROM AUTHOR]

Validating methodology for quantifying of carbon (C) loss from dead wood is critical for understanding C turnover in forest ecosystems. We compared estimates of CO2 fluxes with a closed dynamic chamber method using an infrared gas analyzer with: 1) small chambers installed on the downed woody debris (DWD) surface and 2) DWD segments placed in large chambers. The fluxes were measured from 6 intermediately decayed DWD fragments, wood and bark of Betula pubescens and Populus tremula and calculated on the surface area, volume and mass bases. For most DWD fragments, the tendency with an underestimation of CO2 flux in the first approach up to 90% was observed due to a barrier effect of a thick bark layer and possible gas leakages. Our results demonstrate the importance of taking into account contribution of bark into total DWD respiration rates especially in upscaling the piece-level results into ecosystem level. [ABSTRACT FROM AUTHOR]

A comparative analysis of the copper and iron ions bonds exchange energies was conducted for various variants of orderings and distributions of iron ions among crystallographic positions in ludwigite Cu2FeBO5. Analysis showed that the exchange bonds of iron ions play a key role in the formation of magnetic order. The magnetic ordering strongly depends on the distribution of iron ions among the positions. In the case when the Fe3+ is in the same position as in Fe3BO5, the most favorable magnetic structure is similar to the magnetic structure of ludwigite Fe3BO5. In other cases, the type of magnetic ordering is different. [ABSTRACT FROM AUTHOR]

Electron paramagnetic resonance (EPR) and magnetostriction of the Cu2MnBO5 single crystal have been studied. The EPR spectrum consists of a single Lorentzian line due to the exchange-coupled system of spins of Cu2+ and Mn3+ ions. It has been established experimentally that the g-factor in the paramagnetic region is strongly anisotropic and anomalously small, which is not typical of the exchange-coupled system of spins of Cu2+ and Mn3+ ions. At a temperature of 150 K, the g-factors along the crystallographic a, b, and c axes are 2.04, 1.96, and 1.87, respectively. Such small effective g-factor values can be due to the effect of the anisotropic Dzyaloshinskii–Moriya exchange interaction between the spins of Cu2+ and Mn3+ ions directed along the a axis. The presence of two Cu2+ and Mn3+ Jahn–Teller ions occupying four nonequivalent positions in the crystal is responsible for the absence of the inversion center. It is found that the behavior of the magnetostriction of Cu2MnBO5 is not typical of transition-metal crystals but is closer to the behavior of crystals containing rare-earth ions. [ABSTRACT FROM AUTHOR]

Raman spectra changes in multiferroic Ho1–xNdxFe3(BO3)4(x = 0, 0.25, 0.5, 0.75) and Sm1–yLayFe3(BO3)4(y = 0, 0.75) single crystals at low temperatures have been analyzed. The anomalies corresponding to the phase transition of the second order have been detected at the temperatures of magnetic phase transitions, being consistent with previously reported results of the magnetization study. A number of anomalies in the temperature dependences of the spectral lines associated with the occurrence of magnetic order. A mode corresponding to two-magnon scattering was revealed. Comparison of the features of low-temperature low-frequency spectra of solid solutions Ho-Nd and Sm-La has been carried out. [ABSTRACT FROM PUBLISHER]

The temperature dependences of the magnetic susceptibility in magnetic fields applied parallel and perpendicular to axis с of a Mn0.89Mg1.11BO4 single crystal were measured. Spin ordering typical of an antiferromagnetic with an easy magnetization axis was observed below 16 K. The Dzyaloshinskii–Moriya interaction between spins of manganese ions in Mn0.89Mg1.11BO4 was estimated by analyzing the EPR linewidth. [ABSTRACT FROM AUTHOR]