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Temperature study of magnetic resonance spectra of co-modified (Co,N)-TiO2 nanocomposites

Guskos N., Typek J., Zolnierkiewicz G., Guskos A., Berczynski P., Dolat D., Mozia S., Aidinis K., Kruk K., Morawski A. W.

Materials Science Poland

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2016

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Vol. 34, No. 2

242--250

EN

The (nCo,N)-TiO2 (n = 1, 5 and 10 wt.% of Co) nanocomposites were investigated by magnetic resonance spectroscopy in 4 K to 290 K range. Analyses of ferromagnetic/electron paramagnetic resonance (FMR/EPR) spectra in terms of four Callen lineshape components revealed the existence of two types of magnetic centers, one derived from metallic cobalt nanoparticles in superparamagnetic (SPM) phase and the other from cobalt clusters in the TiO2 lattice. Additionally, at low temperature the EPR spectrum arising from Ti3+ ions was also registered. Both relaxations of the Landau-Lifshitz type and the Bloch-Bloembergen type played an important role at high temperature in determining the linewidths and the latter relaxation was prevailing at low temperature. Analysis of the integrated intensity showed that the SPM signal is due to small size FM cobalt nanoparticles while the paramagnetic signal from Co clusters originates from those nanoparticles in which the concentration of magnetic polarons is below the percolation threshold.

2

FMR study of samples obtained by nitriding and nitrides reduction of nanocrystalline iron

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

Materials Science Poland

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2016

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Vol. 34, No. 1

6--12

EN

Samples obtained by nitriding of promoted nanocrystalline iron and the nitrides reduction at various nitriding potential in terms of thermodynamic parameters were investigated by electron paramagnetic resonance/ferromagnetic resonance (EPR/FMR) method at room temperature. Experimental FMR spectra were fitted by the Dysonian-type resonance lines arising from the presence of different Fe–N phases. The obtained FMR parameters allowed us to identify the component phases and to determine their magnetic properties. In general, the proposed simple method of decomposition of the FMR spectra produced results on the phase content in investigated samples that were consistent with XRD measurements and additionally, magnetic characteristics of the studied nanomagnets.

3

Magnetic resonance study of co-modified (Co,N)-TiO2 nanocomposites

Guskos N., Zolnierkiewicz G., Guskos A., Typek J., Berczynski P., Dolat D., Mozia S., Aidinis C., Morawski A. W.

Nukleonika

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2015

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Vol. 60, No. 3, part 1

411--416

EN

Three nCo,N-TiO2 nanocomposites (where cobalt concentration index n = 1, 5 and 10 wt %) were prepared and investigated by magnetic resonance spectroscopy at room temperature. Ferromagnetic resonance (FMR) lines of magnetic cobalt agglomerated nanoparticle were dominant in all registered spectra. The relaxation processes and magnetic anisotropy of the investigated spin system essentially depended on the concentration of cobalt ions. It is suggested that the samples contained two magnetic types of sublattices forming a strongly correlated spin system. It is suggested that the existence of strongly correlated magnetic system has an essential infl uence of the photocatalytic properties of the studied nanocomposites.

4

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

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

Materials Science Poland

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2014

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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

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

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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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.

6

Magnetic resonance study of γ-Fe2O3 nanoparticles dressed in oxygen based free radicals

Guskos N., Typek J., Zolnierkiewicz G., Wardal K., Guskos A., Berczynski P., Petridis D.

Materials Science Poland

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2013

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Vol. 31, No. 4

587--594

EN

Two composites consisting of g-Fe2O3 (maghemite) nanoparticles covered by two different oxygen-based free radicals derived from a 4-(methylamino)phenol sulphate and 8-hydroxy-1,3,6-trisulfonic trisodium salt acid were prepared and investigated by the magnetic resonance method in the 4 – 300 K range. Both composites displayed broad and very intense ferromagnetic resonance (FMR) lines originating from g-Fe2O3 agglomerated nanoparticles. The FMR spectrum was fitted satisfactorily at each temperature by two Landau-Lifshitz functions reflecting the existence of magnetic anisotropy in the investigated system. The temperature dependence of the obtained FMR parameters (resonance field, linewidth, integrated intensity) was studied and the results were interpreted in terms of magnetic interactions between free radicals and nanoparticle agglomerates. A comparison with previously studied similar systems containing maghemite nanoparticles was made and conclusions about the role of free radicals were drawn.

7

Effect of annealing on EPR spectra of Ti-Si-C-N samples

Guskos N., Anagnostakis E. A., Zolnierkiewicz G., Typek J., Biedunkiewicz A., Guskos A., Berczynski P.

Materials Science Poland

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2012

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Vol. 30, No. 1

23--31

EN

Two nanocrystalline samples of TiC+SiC+20%C (sample 1) and Si3N4+Si(C,N)+Ti(C,N)+1%C (sample 2) were prepared by non-hydrolytic sol-gel method. The latter sample was produced from sample 1, by subjecting it to additional annealing at high temperature. XRD measurements showed the presence of aggregates of cubic SiC+TiC nanoparticles (10 to 30 nm in size). In both samples, a very narrow electron paramagnetic resonance (EPR) line originating from localized magnetic centers was centered at geff2. At T = 130 K, we registered the linewidths DHpp = 1.41(2) G and DHpp = 2.92(2) G for the sample without and with thermal annealing, respectively. For the non-annealed sample, the resonance line was fitted by a Lorentzian line in the low temperature range, and by a Dysonian line above 70 K, which indicates a significant change in electrical conductivity. Therefore, thermal annealing can significantly improve the transport properties of samples. An analysis of the temperature dependence of the EPR parameters (g-factor, linewidth, integrated intensity) showed that thermal annealing has a significant impact on the reorientation processes of localized magnetic centers.

8

Thermal characterization of polymer composites with nanocrystalline maghemite

Maryniak M., Guskos N., Typek J., Petridis D., Szymczyk A., Guskos A., Goracy K., Rosłaniec Z., Kwiatkowska M.

Polimery

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2009

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T. 54, nr 7-8

546-551

EN

Samples of multiblock poly(ether-ester) copolymer doped with magnetic ?-Fe2O3 nanoparticles (at small concentrations of 0.1 wt. % and 0.3 wt. %) have been investigated by DSC method to study the melting and crystallization behavior. Two forms of magnetic ?-Fe2O3 nanoparticle filler were used: solid-state grains and a suspension of ?-Fe2O3 with palmitic acid in toluene. Application of the solid filler caused formation of agglomerates of size of about 20?m while in the suspension form separate nanoparticles were in the range 10-20nm. The thermal and thermo-oxidative stability of composites was analyzed by conventional TGA analysis. The DSC results showed that crystallization and, to a smaller extent, melting, were considerably affected by the introduction of magnetic nanoparticles. The main influence is a shift in the crystallisation temperature up to 20° and melting/glass transition shift up to 6°. Thermogravimetric analysis showed significant enhancement of thermal and thermo- oxidative stability of the composites with respect to pure PEE. The dependence of thermal parameters on the concentration of magnetic filler has shown that the largest agglomerates produced the biggest change in all thermal parameters.

PL

Próbki multiblokowego kopolimeru eterowo-estrowego (PEE) domieszkowano magnetycznymi nanocząstkami ?-Fe2O3 (w ilości 0,1 % mas. lub 0,3 % mas.). Zastosowano dwie postacie napełniacza, mianowicie ziarna polikrystaliczne (tworzące aglomeraty o wymiarze ok. 20?m) lub zawiesiny nanocząstek ?-Fe2O3 w otoczce kwasu palmitynowego w toluenie (wymiar ok. 20nm). Metodą DSC zbadano wpływ tego nanonapełniacza na zjawiska topnienia i krystalizacji uzyskanych kompozytów (tabela 1, rys. 1) a do oceny stabilności termicznej i termooksydacyjnej wykorzystano analizę termograwimetryczną TGA (tabela 2, rys. 2, 3). Stwierdzono, że proces krystalizacji i, w mniejszym stopniu, także topnienia zostały znacznie zmodyfikowane przez obecne w kompozycie nanocząstki magnetyczne. Głównym efektem domieszkowania było podwyższenie temperatury krystalizacji aż o 20° i przesunięcie temperatury przemiany topnienia/zeszklenia o 6°. Analiza TGA wykazała istotniejszy wzrost stabilności termicznej i termooksydacyjnej kompozytów niż niemodyfikowanego PEE, przy czym wzrost ten jest tym wyraźniejszy im większe są aglomeraty.

9

Study of magnetic agglomerates in the nanomaterial system (Ti-Si-C(N))/C by the magnetic resonanse technique

Guskos N., Anagnostakis E. A., Żołnierkiewicz G., Typek J., Likodimos V., Guskos A., Biedunkiewicz A.

Elektronika : konstrukcje, technologie, zastosowania

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2008

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Vol. 49, nr 5

18-21

EN

The nanomaterial system (Ti-Si-C(N)) has been prepared by a sol-gel method in flowing nitrogen atmosphere. In its magnetic response a very wide ESR line has been observed, arising from localized magnetic centers, along with an additional very broad and intense line in low magnetic field. The pertinent EPR/FMR parameters (resonance field, linewidth, integrated intensity) have been calculated and studied versus temperature. Analysis of the obtained temperature evolution of the EPR/FMR parameters has revealed characteristics of magnetic interactions between agglomerates and magnetic-dipole localized systems. Magnetic ordering processes for the localized magnetic centers are considered and discussed connected with traceable magnetic agglomerates being liable to enhance magnetic dipole-dipole interactions.

PL

Nanomateriał (Ti-Si-C(N)) został wytworzony metodą sol-żel w strumieniu gazowego azotu. Widmo ERP tego materiału składa się z bardzo wąskiej linii pochodzącej od zlokalizowanych centrów magnetycznych oraz z dodatkowego silnego i szerokiego sygnału znajdującego się w słabym polu magnetycznym. Obliczono standardowe parametry widma ERP/FMR (pole rezonansowe, szerokość linii, intensywność zintegrowana) oraz zbadano ich zależności temperaturowe. Analiza zmian temperaturowych tych parametrów pozwoliła określić charakterystyki oddziaływań magnetycznych pomiędzy aglomeratami i układem zlokalizowanych dipoli magnetycznych. Rozważono możliwość istnienia procesów uporządkowani magnetycznego w układzie zlokalizowanych centrów magnetycznych, które zostały wzmocnione przez system aglomeratów magnetycznych.

10

FMR study of magnetic nanoparticles embedded in non-magnetic matrix

Guskos N., Anagnostakis E. A., Guskos A.

Journal of Achievements in Materials and Manufacturing Engineering

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2007

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Vol. 24, nr 1

26-35

EN

Purpose: The aim of this review is recapitulating the FMR study of low concentration of magnetic nanoparticles in non-magnetic matrices. Design/methodology/approach: Magnetic nanoparticles exhibit a variety of anomalous magnetic properties and they could be used for forming low concentration in different matrices. This way, they are being found to be allowing for effectively novel applications of FMR (ferromagnetic resonance) for easier trustworthy characterisation of a variety of materials. alpha-Fe, Co, Fe3C, gamma- Fe203, Fe3O4 magnetic nanoparticles have been used as low concentration fillers in paraffin, concrete, resin and polymers/copolymers. Findings: For all these matrices, the intensities of the FMR spectra are recorded decreasing with temperature lowering in the high temperature region, whilst the resonance locus is shifted to the direction of lower magnetic field, essentially changing the resonance condition. These parameters of the FMR spectra are seen depending upon kind of a nanoparticle host in such a way that this method could be useful for studying dynamical processes of the matrices. Interestingly enough, a very low concentration of magnetic nanoparticles embedded in the non-magnetic matrix could modify its glass-state emanation or melting transition. Research limitations/implications: Composite systems containing magnetic nanoparticles promise the potential for high-density data storage, biomedical applications, catalysis, and nanotechnology sensor materialisation among other envisaged utilisations. Originality/value: Continue attempting to decipher the mystery and fruitfulness of magnetic nanoparticle distributions.