Search results

1

Competing Magnetic Interactions in Zn_3Fe_4V_6O_{24} Studied by Electron Paramagnetic Resonance

100%

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

Acta Physica Polonica A

|

2006

|

vol. 109

|

issue 4-5

675-679

EN

A multicomponent vanadate M_3Fe_4V_6O_{24} sample with non-magnetic M = Zn(II) ions was synthesized by the solid state reaction method using stoichiometric mixtures of the 80mol% FeVO_4 and 20mol% Zn_3(VO_4)_2. The temperature dependence of the EPR spectra was performed in the 90-280 K temperature range. The resonance field and the integrated intensity of the EPR line showed minimum value of both parameters at≈200 K. It is suggested that a part of the sample is displaying tendency to form an antiferromagnetic ordered state (or the magnetic clusters) above this temperature while below the ferromagnetic interaction of the main part of material is dominating. This behaviour is attributed to the inherent magnetic inhomogeneity of the system due to the presence of the ferromagnetic or antiferromagnetic spin clusters.

2

Dynamic Orbit-Lattice Interactions for PbF_{2}:Gd^{3+} Single Crystals

100%

Kuriata J., Rewaj T., Guskos N.

Acta Physica Polonica A

|

1991

|

vol. 79

|

issue 4

531-541

EN

Temperature dependence of the second-order spin-lattice coefficients for PbF_{2}:Gd^{3+} is reported. It is shown that the thermal expansion of the crystal lattice contributes only in about 14 % to the observed dependence and the rest should be ascribed to a dynamic coupling between the 4f^{7} electrons and lattice vibrations. The results are parametrized in both the Einstein and the Debye models and it is shown that the phenomenological parameters obtained from such parametrization can be made to coincide in both models if a specific value of the Einstein frequency ω_{E} is properly chosen. Both models of parametrization show that the Γ_{3}_{g} vibrating mode couples to the 4f^{7} electrons much weaker than the Γ_{5}_{g} one.

3

Temperature Dependence of the EPR Spectra of the Nanocrystalline TiN and TiC Dispersed in a Carbon Matrix

100%

Guskos N., Bodziony T., Biedunkiewicz A., Aidinis K.

Acta Physica Polonica A

|

2005

|

vol. 108

|

issue 2

311-316

EN

Two powder samples: nanocrystalline titanium carbide (TiC) and titanium nitride (TiN) dispersed in a carbon matrix were synthesized by a nonhydrolytic sol-gel process. Both samples were characterized by the X-ray diffraction and transmission electron microscopy. The transmission electron microscopy examination of the TiC and TiN nanoparticles showed that their average crystalline size was about 20 nm. The temperature dependence of the EPR spectra for both samples was measured in 10 K to 200 K temperature range. A similar very narrow (about 0.2 mT) EPR line centered at g≈2 (at room temperature) was recorded in both samples. The EPR line observed in both samples is arising from electron conductivity centers dispersed in the carbon matrix and it was fitted by Dysonian line shape. The temperature dependence of the EPR spectrum showed different behavior of these two samples. It is suggested that in the sample TiC/C multiwall carbon nanotubes are formed while in the sample TiN/C the graphite structure dominates.

4

Spin-Phonon Contributions to the b^{0}_{2} Parameter for Gd^{3+} in RbCdF_{3} Single Crystals

100%

Guskos N., Kuriata J., Rewaj T.

Acta Physica Polonica A

|

1992

|

vol. 81

|

issue 6

659-665

EN

Temperature dependence of the b^{0}_{2} spin-hamiltonian parameter for Gd^{3+} in RbCdF_{3} single crystals is described. The dependence is interpreted in terms of the 4f^{7} electrons coupling to the whole phonon spectrum of the crystal. The presented data give also an insight into the dynamics of charge compensators causing a tetragonal distortion of the crystal field.

5

Low Concentration Effect of Fe_3O_4 and Fe_3C Magnetic Nanoparticles in Non-Magnetic Matrix on the FMR Spectra

76%

Bodziony T., Guskos N., Roslaniec Z., Narkiewicz U., Kwiatkowska M., Maryniak M.

Acta Physica Polonica A

|

2005

|

vol. 108

|

issue 2

297-302

EN

PTMO-block-PET polymer filled with a low concentration (0.1 wt.%) of binary magnetic system: magnetite (Fe_3O_4) and iron carbide (Fe_3C) with carbon (C) was prepared. Characterization of the sample was done by using X-ray diffraction and scanning electron microscopy methods. Temperature dependence of the FMR spectra was carried out in the 10-300 K temperature range. The extraordinary temperature dependence behaviour of FMR spectra was recorded. The FMR spectra were fitted by two Lorentzian lines originating from magnetite and iron carbide. The anomalous behaviour of FMR spectra below 100 K could be explained by the skin effect or by the freezing of the matrix benzene rings at about 115 K. The temperature dependence of the g parameter below 75.5 K (opposite shift of the resonance field to usually observed) was interpreted as a result of strong antiferromagnetic interaction of some portion of agglomerates.

6

Magnetic Study of Phases in FeVO₄-Co₃V₂O₈ System

76%

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

Acta Physica Polonica A

|

2017

|

vol. 132

|

issue 1

24-30

EN

Magnetic properties of four nFeVO₄/(1-n)Co₃V₂O₈ samples obtained in reactions between FeVO₄ and Co₃V₂O₈ (n = 0.96, 0.86, 0.84 and 0.83, samples designated S1, S3, S4, S5, respectively) have been investigated by DC magnetisation in field cooling and zero-field-cooling modes and EPR. DC magnetic susceptibility showed paramagnetic behavior of all samples in high-temperature range (T > 20 K) and transition to antiferromagnetic state at 16-18 K (depending on sample iron content). Additional magnetic freezing at 8 K was registered for S3-S5 samples containing larger amount of cobalt. The Curie-Weiss law in 100-300 K temperature range indicates that Co²⁺ is in the high-spin state (S = 3/2). From the parameters of the hysteresis loop observed for the samples it was calculated that 0.58% of all magnetic (Fe³⁺, Co²⁺) ions were involved in the ferromagnetic states. EPR spectra of the samples were recorded in high temperature range (T > 90 K). The temperature dependence of the spectral parameters (resonance field, linewidth, integrated intensity) suggested the Fe³⁺ high-spin ions coupled by antiferromagnetic interaction and clusters of ions play major role in EPR spectra.

7

Magnetic Resonance Study of MnO/ZnO Nanopowders

76%

Guskos N., Zolnierkiewicz G., Typek J., Sibera D., Narkiewicz U., Łojkowski W.

Acta Physica Polonica A

|

2011

|

vol. 120

|

issue 6

1074-1079

EN

Fine particles n(MnO)/-(1-n)ZnO (n = 0.05 to 0.95) were prepared by wet chemistry method. According to X-ray diffraction analysis the obtained samples with n = 0.95, 0.90, 0.80, 0.70, 0.60 contained Mn_3O_4 and ZnMn_2O_4 phases, while samples with n = 0.05, 0.10, 0.20, 0.30, 0.40 and 0.50 contained ZnMnO_3 and ZnO phases. The mean crystalline size of ZnMnO_3 varied from 8 to 13 nm. The magnetic resonance investigations have been carried out at room temperature. Slightly asymmetric, broad and intense magnetic resonance line is recorded for all samples. The magnetic resonance spectra parameters showed marked differences depending on the composition index n. This could be explained by the variation of the magnetic susceptibility and a much slower evolution of spin relaxation, associated with the interaction of crystal field and superexchange interactions. Taking into account the values of magnetic resonance parameters, the investigated samples could be divided into two groups: these with the composition index n<0.50 and those with n>0.50. A detailed discussion of the magnetic properties of different phases in the n(MnO)/-(1-n)ZnO system is presented.

8

FMR Study of Temperature Dependence of Magnetic Properties of Nanocrystalline 0.90(Fe_2O_3)/0.10ZnO

76%

Guskos N., Glenis S., Zolnierkiewicz G., Typek J., Sibera D., Narkiewicz U.

Acta Physica Polonica A

|

2011

|

vol. 120

|

issue 6

1070-1073

EN

The nanocrystalline mixed system 0.90(Fe_2O_3)/-0.10ZnO has been prepared by coprecipitation and calcination processes. The phase composition of samples was determined by X-ray diffraction. The studied nanocrystalline sample is dominated by phase Fe_2O_3 but very small amounts of ZnO and ZnFe_2O_4 phases were also identified. The ferromagnetic resonance investigations of the obtained sample have been carried out in the temperature range from liquid helium to room temperature. The asymmetrical and very intense magnetic resonance line was recorded at all temperatures. A significant shift of spectra towards lower magnetic fields with decreasing temperature was observed. A very good fitting by two Lorentzian functions has been obtained which suggested the existence of a strong anisotropic magnetic interaction. Some similarities in behaviour of ferromagnetic resonance parameters of the present sample and the 0.95Fe_2O_3Fe2O3/0.05ZnO sample were noticed but the parameters values were essentially different. The gradients Δ H_{r}/Δ T (where H_{r} is the resonance field), the broadening processes of the resonance lines as well as the line amplitudes were changing more intensely changing with temperature in comparison to sample 0.95Fe_2O_3Fe2O3/0.05ZnO. The following values Δ H_{r}/Δ T are obtained: 16.7(1) Gs/K and 20.7(1) Gs/K over the 60 K temperatures where below 40 K is 41.5(1) Gs/K and 56.0(1) Gs/K. The reorientation processes were more active at low temperatures for smaller concentrations of magnetic nanoparticles.

9

Charge Transfer and f-f Transitions Studied by Photoacoustic Spectroscopy of [R(NO_3)_2(PicBH)_2]NO_3 and [R(NO_3)_3(PicBH)_2] Complexes (R - Rare Earth Ion)

64%

Guskos N., Papadopoulos G., Majszczyk J., Typek J., Wabia M., Likodimos V., Paschalidis D., Tossidis I., Aidinis k.

Acta Physica Polonica A

|

2003

|

vol. 103

|

issue 2-3

301-313

EN

High-resolution photoacoustic spectra of trinitrato-bis[N-(2-pyridyl-methylene)-N'-benzoyl-hydrazine]R (III), (R = La, Ce, Pr), and binitrato-bis[N-(2-pyridylmethylene)-N'-benzoyl-hydrazine]R(III) nitrate (R=Y, Nd, Eu, Yb, Tb, Gd, Ho, Dy, Er) complexes, in the visual region, were studied for powder samples. Very intense photoacoustic spectra of various shapes were attributed to the intraligand transitions of the π → π* type located mainly on the C=N group and the n → π* transitions located on the carbonyl group. The intensity of these transitions essentially depends on the type of rare earth ions. The existence of f-f electron transitions could influence the relaxation processes, which play an important role in intensity determination of the above transitions. For many investigated samples the energy levels of excited states of rare earth ions were identified (f-f electron transitions). The radiation energy for some of the rare earth ions were compared with the d-d electron transitions of certain copper(II) organometallic complexes, which are very important in biogenic systems. The correlation between ions with localized and extended wave functions is suggested.

10

Magnetic Resonance and Dielectric Studies of a Nonlinear La_3Ga_{5.5}Ta_{0.5}O_{14} Single Crystal Doped with Erbium

64%

Bodziony T., Typek J., Orlowski M., Majszczyk J., Wabia M., Berkowski M., Ryba-Romanowski W., Guskos N., Likodimos V., Anagnostakis E.

Acta Physica Polonica A

|

2003

|

vol. 103

|

issue 2-3

315-322

EN

Single crystal of erbium doped La_3Ga_{5.5}Ta_{0.5}O_{14} grown by the Czochralski method have been investigated by electron paramagnetic resonance and dielectric spectroscopy methods. Dielectric permittivity ε measurements performed in 90-440 K temperature range have shown negligible dispersion for 1 kHz - 1 MHz frequencies and a Curie-Weiss type behaviour with C=47700 K andθ=-340 K. Electron paramagnetic resonance studies have revealed the presence of two different paramagnetic, monoclinic centres. The calculated g factor values are: g_1=1.449, g_2=11. 534, g_3=4.24 for the main M_1 centre and g_1=1.98, g_2=4.169, g_3=4.25 for the weaker M_2 centre. The temperature dependence of EPR line intensity for centre M_1 and M_2 is quite different - while lines attributed to M_1 could only be observed at low temperatures, below 20 K, lines of M_2 centre persisted up to 200 K. The M_1 centre is connected with Er^{3+} ion entering substitutionally into La^{3+} site, while M_2 is probably connected with 3d ions at the same site, unintentionally introduced into the material as an admixture.

Refine search results

Competing Magnetic Interactions in Zn_3Fe_4V_6O_{24} Studied by Electron Paramagnetic Resonance

Dynamic Orbit-Lattice Interactions for PbF_{2}:Gd^{3+} Single Crystals

Temperature Dependence of the EPR Spectra of the Nanocrystalline TiN and TiC Dispersed in a Carbon Matrix

Spin-Phonon Contributions to the b^{0}_{2} Parameter for Gd^{3+} in RbCdF_{3} Single Crystals

Low Concentration Effect of Fe_3O_4 and Fe_3C Magnetic Nanoparticles in Non-Magnetic Matrix on the FMR Spectra

Magnetic Study of Phases in FeVO₄-Co₃V₂O₈ System

Magnetic Resonance Study of MnO/ZnO Nanopowders

FMR Study of Temperature Dependence of Magnetic Properties of Nanocrystalline 0.90(Fe_2O_3)/0.10ZnO

Charge Transfer and f-f Transitions Studied by Photoacoustic Spectroscopy of [R(NO_3)_2(PicBH)_2]NO_3 and [R(NO_3)_3(PicBH)_2] Complexes (R - Rare Earth Ion)

Magnetic Resonance and Dielectric Studies of a Nonlinear La_3Ga_{5.5}Ta_{0.5}O_{14} Single Crystal Doped with Erbium