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1

Study of magnetic inhomogeneity in b-Cu3Fe4V6O24

100%

Guskos N. , Zolnierkiewicz G. , Typek J. , Szymczak R. , Blonska-Tabero A.

Materials Science Poland

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2012

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tom Vol. 30, No. 1

1--9

EN

The temperature dependence of dc magnetization and electron paramagnetic resonance (EPR) spectra of the b-Cu3Fe4V6O24 multicomponent vanadate were investigated. Dc magnetic measurements showed the presence of strong antiferromagnetic interactions (Curie-Weiss temperature, Q 80 K) at high temperatures, while zero-field-cooled (ZFC) magnetization revealed a cusp-like maximum in low fields at Tf 1 =4.4 K, which coincides with the splitting of the ZFC and FC curves. Another maximum was registered at Tf 2 = 3.0 K. These two temperatures (Tf 1 and Tf 2) could be regarded as freezing temperatures in the spin glass state of two magnetic sublattices of Fe1 and Fe2 ions. The EPR spectrum of b-Cu3Fe4V6O24 is dominated by a nearly symmetrical, very intense and broad resonance line centered at geff 2.0 that could be attributed to iron ions. Below 10 K, an additional EPR spectrum with g1 = 2.018(1) and g2 = 2.175(1) appears, as well as a very weak line at geff = 1.99(1). The former spectrum is probably is due to divalent copper ions, and the latter line due to vanadium V4+ complexes. The temperature dependence of EPR parameters (g-factor, linewidth, integrated intensity) was determined in the range of 3 - 300 K. Two low-temperature maxima in the temperature dependence of the integrated intensity (at 40 and 6 K) were fitted with a function suitable for pairs of exchange-coupled Fe3+ ions. A comparison of dc magnetic susceptibility and EPR integrated intensity indicates the presence of spin clusters, which play an important role in determining the low-temperature magnetic response of b-Cu3Fe4V6O24.

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.

Materials Science Poland

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2005

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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

High temperature EPR study of the M3Fe4V6O24 (M = Cu, Zn, Mg and Mn)

86%

Guskos N. , Zolnierkiewicz G. , Typek J. , Pilarska M. , Aidinis C. , Blonska-Tabero A.

Materials Science Poland

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2016

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tom Vol. 34, No. 3

517--522

EN

Electron paramagnetic resonance (EPR) spectra of M3Fe4 V6 O24 (M = Cu, Zn, Mg and Mn) compounds in high temperature range (293 K to 493 K) have been investigated. The role of magnetic (Cu, Mn) and non-magnetic (Zn, Mg) ions in M3Fe4 V6 O24 structure in formation of magnetic resonance spectra was studied. Temperature dependence of EPR parameters: resonance field, linewidth and integrated intensity were examined. Similarities and differences in temperature behavior of these parameters has been discussed in terms of different relaxation mechanisms and magnetic interactions in the spin systems. An important role of additional magnetic ions (M = Mn or Cu) in the M3Fe4 V6 O24 structure has been identified and its consequences considered.

4

Study of magnetic properties of two samples from FeVO4-Co3V2O8 system

86%

Guskos N. , Zolnierkiewicz G. , Typek J. , Szymczak R. , Guskos A. , Berczynski P. , Blonska-Tabero A.

Materials Science Poland

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2013

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tom Vol. 31, No. 4

601--610

EN

Two samples containing phases formed in the FeVO4–Co3V2O8 system were prepared by a conventional sintering method. The sample designated as H5 was one-phase with the howardevansite-type structure, while the sample designated as HL7 contained a mixture of H-type and lyonsite-type structures. The temperature dependence of the electron paramagnetic resonance (EPR) spectra and static magnetic susceptibility c was investigated in the temperature range from liquid helium to room temperature. Both the EPR spectra and the dc magnetic susceptibility showed anomalous behavior indicating that the magnetic competition process may be responsible. A comparison of the obtained results with previous studies on related compounds with the same structure, i.e. M3Fe4V6O24 (M = Mg(II), Zn(II), and Cu(II)) revealed that the observed anomaly shifted to lower temperatures on replacing the non-magnetic ions by magnetic Co(II) ions. The temperature dependence of the inverse susceptibility c􀀀1 indicates the existence of antiferromagnetic interactions between Fe(III) and Co(II) spins in sample H5. The obtained values of the Curie-Weiss temperatures are lower than for the Mn3Fe4V6O24 compound and comparable to compounds from M3Fe4V6O24 systems with M diamagnetic cations. The introduction of cobalt cations intensifies the magnetic frustration what is reflected in the temperature dependence of the magnetic susceptibility at low temperatures.

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.

Materials Science Poland

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2005

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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.