Dependence of nickel ferrite EMR absorption coefficient on the method of preparation

Nickel ferrites are among the most abundant members of the soft magnetic materials. In the last few decades, the interest for new methods of their preparation has increased, due to the fact that physical and chemical properties of these materials depend strongly on preparation conditions. In this paper, samples of NiFe2O4 were synthesized by standard sintering and via a chemical procedure from complex compounds with acetylacetonato ligands. Formation of the NiFe2O4 spinel phase was monitored by SEM, TEM, and XRID measurements. Average particle size was 20x20x4 nm (slabs). Masurements of the real and imaginary parts of permittivity and permeability were conducted on the obtained nickel ferrite samples in the 7-12 GHz frequency range. In addition to this, the electromegnetic radiation (EMR) absorption coefficient was calculated for all samples, using the Nicolson-Ross analysis. Examination of the obtained results lead to the conclusion that the method of synthesis, as well as final particle size, influence the EMR absorption coefficient in the observed frequency range.