O. A. Bayukov

Mössbauer study of bacterial ferrihydrite

Mössbauer measurements reveal four inequivalent Fe sites in ferrihydrite produced by Klebsiella oxytoca. The origin of these sites can be understood in terms of two nanosized structural regions in the bacterium and a certain ordering of bilayers and single layers of Fe-occupied octahedra.

Iron-containing nanoparticles from microbial metabolism

We have studied the crystal structure and magnetic properties of Fe-containing nanoparticles formed as a result of microbial metabolism. Our experimental data, coupled with earlier results, suggest that the nanoparticles consist of ferrihydrite, Fe2O3 · nH2O, and are in a superparamagnetic state.

Mössbauer Study of Magnetic Microspheres Isolated from Power Plant Fly Ash

The phase composition of magnetic microspheres isolated from Ekibastuz coal fly ash in six narrow size ranges is determined by Mössbauer spectroscopy. The major phase in the microspheres is nonstoichiometric, cation-substituted (Al, Mg, and Ti) magnetite. Their magnetic properties are shown to depend on the Fe content and cation distribution over the spinel sites.

Synthesis and magnetic properties of Cu3B2O6 single crystals

The temperature dependence of the magnetic susceptibility of Cu3B2O6 single crystals grown by spontaneous crystallization from a melt consisting of a mixture of CuO and B2O3 and the behavior of their magnetization are investigated in magnetic fields up to 55 kOe. A broad susceptibility maximum is observed near 39 K, and a sharp drop in susceptibility is observed at T<10 K. The paramagnetic Néel temperatures for all orientations of the magnetic field in the crystal investigated are negative, attesting to the predominantly antiferromagnetic character of the exchange interactions. The effective magnetic moment of the Cu2+ ion is anisotropic and lies in the range from 1.054μB to 1.545μB. The magnetization depends linearly on magnetic field at T>10 K, whereas at temperatures below 10 K a discontinuity is observed at fields of the order of 40 kOe. At room temperature, electron magnetic resonance characterized by an almost isotropic g factor (g=2.165) is detected at 36.22 GHz. The exchange interactions in Cu3B2O6 are analyzed on the basis of the Goodenough-Kanamori rules. The possibility of the establishment of a singlet magnetic state in the crystal is analyzed.

Synthesis of the new oxocuprate Cu5Bi2B4O14 and investigation of its structural, magnetic, and resonant properties

AbstractSingle crystals of the new compound Cu5Bi2B4O14 are grown and its structural, magnetic, and resonant properties are investigated for the first time. It is found that the Cu5Bi2B4O14 crystal synthesized has a triclinic symmetry with space group

Magnetic and electrical properties of Fe1.91V0.09BO4 warwickite

P\bar 1

Magnetic phase diagram of the olivine-type Mn2GeO4 single crystal estimated from magnetic, resonance and thermodynamic properties

and the unit cell parameters a=10.132 Å, b=9.385 Å, c=3.458 Å, α=105.443°, β=97.405°, γ=107.784°, and Z=1. At a temperature of 24.5 K, the crystal undergoes a magnetic phase transition to the magnetically ordered state. The assumption is made that the ferrimagnetic structure of the Cu5Bi2B4O14 crystal consists of two ferromagnetic sublattices coupled through the antiferromagnetic exchange interaction. The unit cell of the crystal contains five copper ions, of which one ion belongs to the first sublattice and the other four ions form the second sublattice. Analysis of the resonant and magnetic static properties demonstrates that the Cu5Bi2B4O14 crystal exhibits an easy-axis magnetic anisotropy. The direction of the easy axis coincides with the c axis of the crystal, whereas the a and b axes are the hard magnetic axes with saturation fields approximately equal to 25 and 10 kOe, respectively.

Specific features of the crystal structure and magnetic properties of the DyFeTi2O7 compound

Solid-state synthesis in Ni/Fe/MgO(001) bilayer epitaxial thin films has been studied experimentally. The phase sequence Fe/Ni→(∼350°C)Ni3Fe→(∼400°C)NiFe→(∼ 550°C)γpar is formed as the annealing temperature increases. The crystal structure in the invar region consists of epitaxially intergrown single-crystal blocks consisting of the paramagnetic γpar and ferromagnetic NiFe phases, which satisfy the orientation relationship [100](001)NiFe ∥ [100](001) γpar. It has been shown that the nucleation temperatures of the Ni3Fe, NiFe, and γpar phases coincide with the temperatures of solid-state transformations in the Ni-Fe system.