Papers by Author: Eugene P. Yelsukov

Abstract: The structural-phase composition, magnetic and microwave properties of Fe_x(SiO₂)_1-x (x=30, 70, 90, 95) nanocomposites have been studied. The composites are produced by high-energy ball milling with either Ar or acetone as a milling medium and milling time of 1 to 64 h. The microwave magnetic properties of the composite in the frequency range of 0.1 to 6 GHz are shown to depend slightly on the phase composition and be governed mainly by the particle size. Reduction of the particle size to about 1 μm results in elimination of magnetic loss at frequencies below 1 GHz, which is attributed to the domain walls motion.

Abstract: The results of X-ray diffraction, complex in-field (up to 9 T) and temperature (5300 К) Mössbauer and magnetometric studies of the ordered Fe₆₅Al_35-хM_х (M=Ga, B; x=0,5,10) and Fe_65-хV_xAl₃₅ (x=5,10) alloys are presented. Analysis of the magnetometry studies shows that the systems Fe₆₅Al₃₅ и Fe₆₅Al_35-хGa_х (x=5, 10) are characterized by two different magnetic states with essentially distinguishing hysteresis loops and AC susceptibility values. The temperature and external magnetic field values inducing the transition from one magnetic state to another are higher in the Ga-doped alloys than in the reference Fe₆₅Al₃₅ alloy. The boron addition transforms the magnetic state of the initial alloy Fe₆₅Al₃₅ into a ferromagnetic one exhibiting high magnetic characteristics. Substitution of V for Fe in the ternary alloys Fe_65-хV_xAl₃₅ results in reduction of magnetic characteristics and collapsing of ⁵⁷Fe hyperfine magnetic filed.

Abstract: The structure and microwave properties of composites consisting of paraffin as a dielectric host matrix and Fe particles as inclusions have been studied. The composites were prepared by the mechanochemical synthesis and contain 7.7% vol. concentration of the inclusions. The microwave properties were studied in 0.1 to 6 GHz frequency range. The microwave properties of the composites are shown to depend mostly on the size and shape of the inclusions, with the phase composition of the inclusions exerting only a slight effect. With decreasing the inclusions size, the low-frequency peak (300−400 MHz) attributed to the domain wall motion diminishes.

Abstract: The structure and microwave magnetic performance of Fe, Fe-Si-C, and Fe-Co-Si-C powders fabricated by mechanical milling has been studied. The study was aimed at revealing of the effect of shape, composition, and structure of the powder particles on the microwave frequency dispersion of permeability of the powder-filled composites in the frequency range of 0.1−3 GHz. At low frequencies, below 1 GHz, the main reason causing the differences in the microwave magnetic properties of the powders is the shape of powder particles. At higher frequencies, the magnetic performance is mainly due to the effect of eddy currents and is determined by the size of powder particles. The difference in the composition of the powders under study and, therefore, corresponding differences in intrinsic permeability of these have a minor effect on the microwave magnetic performance as compared to the effects of particle size and shape.

Abstract: The results of magnetometric, Mössbauer and XMCD (X-ray Magnetic Circular Dichroism) studies of B2 or DO3–type ordered (25 to 35 at.%Al) and disordered by mechanical activation (35 to 60 at.% Al) Fe-Al alloys are considered. For the description of magnetic characteristics of the studied alloys the validity of local magnetic moments models is discussed. The models suppose that Fe atom local magnetic moments are collinear with magnitude and direction depending on the number of Al atoms in the Fe nearest neighbourhood.