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Magnetic studies of 0.7(Fe2O3)/0.3(ZnO) nanocomposites in nanopowder form and dispersed in polymer matrix

Typek J., Wardal K., Zolnierkiewicz G., Szymczyk A., Guskos N., Narkiewicz U., Piesowicz E.

Materials Science Poland

2016

Vol. 34, No. 2

286--296

Magnetic properties of 0.7(Fe2O3)/0.3(ZnO) nanocomposite synthesized by traditional wet chemistry method and containing only two phases: ZnO (nonmagnetic) and Zn Fe2O4 (magnetic, with nanocrystallites of average size 12 nm, but forming large agglomerates, up to 100 nm in size) were studied by DC magnetization and ferromagnetic resonance (FMR). The investigated nanocomposite was either in a form of nanopowder or dispersed at concentration of 0.1 wt.% in poly(ethylene naphthalate-block-tetramethylene oxide) PTMO-b-PEN polymer matrix. Similarities and differences in magnetic behavior of these two samples revealed by the study of static magnetization and FMR spectra have been discussed relative to different morphologies and the associated variation of interparticle interactions. Moreover, thermal and thermo-oxidative stability of the nanocomposite and the neat polymer have been studied by thermogravimetric method.

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

2013

Vol. 31, No. 4

587--594

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.