Nanocomposites and nanomaterials

Interparticle interactions in polymer-nanoferrite composites and their manifestation in ferromagnetic resonance spectra
Tovstolytkin A.I.1, Polek T.I.1, Fedorchuk O.P.2, Solopan S.O.2, Belous A.G.2
1Institute of Magnetism of the NAS of Ukraine and MES of Ukraine, 36-b Vernadsky Blvd., Kyiv 03142, Ukraine.
E-mail: atov@imag.kiev.ua 
2V.I. Vernadsky Institute of General and Inorganic Chemistry of the NAS of Ukraine, 32/34 Palladina Ave., Kyiv 03142, Ukraine.

In nanostructured magnetic materials, interactions between magnetic nanoobjects may lead to a formation of collective states and result in a strong transformation of macroscopic parameters. There has been strong evidence that long-range magnetic dipole interactions play a non-negligible role even in the samples with a low concentration of magnetic component and that the role of exchange interactions comes to the fore when nanoobjects are in close proximity. At the same time, deep understanding of the processes originated from these interactions have yet remained an obscure issue in modern nanotechnology. In this work, ferromagnetic resonance (FMR) studies have been carried out on the polymer-nanoferrite composites to understand the regularities of the manifestation of interparticle interactions in FMR spectra.
The samples for investigation were prepared with the use of photopolymer Permabond UV630 and Ni0.75Zn0.25MnO4 nanoparticles. The composite films were fabricated on polycrystalline α-Al2O3 substrates by screen printing method, covered with glass protecting plates and polymerized under UV light. Angle and temperature dependences of FMR spectra were studied for the samples with different concentrations of the magnetic component.
Based on the analysis of the experimental data, main features of the evolution of the parameters of FMR spectra in dependence on magnetic nanoparticles concentration are clarified. A critical concentration, at which the manifestation of interparticle interactions in transformation of macroscopic parameters becomes noticeable, is determined. The conclusions about the effect of interparticle interactions on the evolution of macroscopic magnetic parameters of composite structures are made.
The work is partially supported by the State Fund for Fundamental Research of Ukraine (Grant No. F76/34-2018).