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1

Electronic properties of M2InV3O11 (M(II) = Zn(II) and Co(II)) compounds

100%

Guskos N. , Glenis S. , Karkas K. , Zolnierkiewicz G. , Bosacka M.

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tom Vol. 31, No. 1

25-28

EN

The electronic properties of multicomponent vanadate oxides M2InV3O11 (M(II) = Zn(II) and Co(II)) were investigated by electrical resistivity and electron paramagnetic resonance (EPR) measurements. Replacement of non-magnetic Zn(II) cations with magnetic Co(II) ions resulted in a significant drop in the electrical conductivity and an increase in the activation energy. The EPR spectroscopy revealed the presence of VO2+ vanadyl ions in both compounds, while the presence of divalent cobalt ions was identified in the Co2InV3O11 oxide at low temperatures. The concentration of VO2+ vanadyl ions was found to be about one order higher for the vanadate oxide without magnetic ions. It is suggested that the increased concentration of VO2+ ions could be responsible for the enhanced conductivity of Zn2InV3O11.

2

Magnetic resonance study of M3Fe4V6O24 (M = Mg, Zn, Mn, Cu, Co) compounds

86%

Guskos N. , Typek J. , Zolnierkiewicz G. , Blonska-Tabero A. , Kurzawa M. , Bosacka M.

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tom Vol. 23, No. 4

923--928

EN

Multicomponent vanadates, M3Fe4V6O24 (M = Mg(II), Mn(II), Zn(II), Co(II) and Cu(II)), have been synthesized by the solid-state reaction method using a stoichiometric mixture of MO, Fe2O3, and V2O5 oxides. They crystallize in the triclinic space ace group P1 and have a complicated structure with two metal ion subsystems. Electron paramagnetic resonance (EPR) measurements have been performed at room temperature and an intense, almost symmetric EPR lines were recorded for all investigated samples except Co3Fe4V6O24. The integral intensity and linewidth of this line essentially depends on the kind of M(II) metal ion in the crystalline matrix. The EPR line intensity for the sample Co3Fe4V6O24 is over one order of magnitude smaller than for all other investigated compounds, and the position of its resonance line is shifted towards lower magnetic fields. The difference in linewidths and intensities are due to the various magnetic interactions between magnetic ions in the lattice, especially for systems containing two different magnetic ions.

3

Magnetic characterization of nanocrystalline iron samples with different size distributions

86%

Typek J. , Zolnierkiewicz G. , Pelka R. , Kielbasa K. , Arabczyk W. , Guskos N.

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tom Vol. 32, No. 3

423—429

EN

Nanocrystalline iron was obtained by fusing magnetite and promoters. The oxidized form was reduced with hydrogen and passivated (sample P0). The average nanocrystallite size in sample P0 was d(P0) =16 nm and the width of size distribution was s(P0) = 18 nm. Samples of nanocrystalline iron with narrower diameter ranges and larger and smaller average crystallite sizes were also synthesized. They were: sample P1 (d(P1) = 28 nm, s(P1) = 5 nm), sample P2 (d(P2) = 22 nm, s(P1) = 5 nm), sample P3 (d(P3) = 12 nm, s(P1) = 9 nm). These four samples were studied at room temperature by dc magnetization measurements and ferromagnetic resonance at microwave frequency. Correlations between samples sizes distributions (average size and width of the sizes) and magnetic parameters (effective magnetization, anisotropy field, anisotropy constant, FMR linewidth) were investigated. It was found that the anisotropy field and effective magnetization determined from FMR spectra scale linearly with nanoparticle sizes, while the effective magnetic anisotropy constant determined from the hysteresis loops decreases with nanoparticle size increase.

4

Ferromagnetic and spin wave resonances in thin layer of expanded austenite phase

86%

Typek J. , Guskos N. , Zolnierkiewicz G. , Berczynski P. , Guskos A. , Baranowska J. , Fryska S.

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tom Vol. 32, No. 2

198—205

EN

Four samples of austenite coatings deposited by reactive magnetron sputtering on silicon substrate at four different temperatures and pressures were investigated by ferromagnetic resonance (FMR) method at room temperature. The expanded austenite phase S (gN) layers with thickness in the 160 – 273 nm range and concentration of magnetic atoms: 72 % Fe, 18 % Cr and 10 % Ni, were obtained. The coatings with nanometric size grains were strongly textured and grown mostly in [100] direction, perpendicular to the sample surface. Intense FMR spectra were recorded at various angles between the static magnetic field direction and the sample surface. A strong magnetic anisotropy of the main uniform FMR mode was observed and the effective magnetization 4πMe f f determined. Spin wave resonance (SWR) modes were observed in all investigated samples in out-of-plane geometry of the magnetic field. The resonance fields of SWR modes in our samples varied linearly with the spin wave mode number. The value of the effective magnon stiffness constant was determined assuming a parabolic shape of the magnetization variation across the sample thickness.

5

Neutron diffraction study of Mn3Fe4V6O24

72%

Bezkrovnyi A. , Guskos N. , Typek J. , Ryabova N. Y. , Bosacka M. , Blonska-Tabero A. , Kurzawa M. , Rychlowska-Himmel I. , Zolnierkiewicz G.

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tom Vol. 23, No. 4

883--890

EN

Mn3Fe4V6O24 compound was prepared using the solid-state reaction method. The magnetic and crystal structural studies were carried out by using neutron diffraction methods at the temperatures of 10 and 290 K. Down to 10 K no long-range magnetic order was observed. Essential differences in the positions of metal ions were observed as compared to similar systems (ß-Cu3Fe4V6O24 and Zn3Fe4V6O24) investigated by X-ray and neutron diffraction methods. In this system, a disordering process involving iron and manganese atoms in M(2), M(3), M(4) cation sites was found, which could be responsible for the significant differences in the physical properties observed for this type of compound.