Tailoring functional properties of Ni nanoparticles-acrylic copolymer composites with different concentrations of magnetic filler

Magnetic composites with nickel nanoparticles synthesized by the method of the electrical explosion of wire were prepared with acrylic copolymer containing 95 wt. % of butylacrylate and 5 wt. % of methacrylic acid. Two series of composites were made with Ni content covering the range from 5 to 90 wt. % and differing in the degree of aggregation. In one series of composites, the aggregates were irregularly shaped globules with dimensions varying in 1-40 μm range. In the other, chain-like fragments were observed. As expected, the saturation magnetization value of the composites showed a linear dependence on concentration but the coercive field was slightly higher for the aggregated case for a given concentration. Microwave absorption studies of the composites showed both strong zero field absorption and ferromagnetic resonance (FMR). The FMR results were different for the two types of samples; however, each set can be explained by taking into account the distribution of local magnetic fields due to random positions of the particles.