Speaker
Description
Modern times and the associated rapid expansion of science and technology emphasize the need for new materials. This work deals with the analysis of the results of selected types of measurements, which can be used to determine the structural and magnetic properties of nickel-zinc ferrites with spinel structure. These are soft magnetic materials that have extensive use in various applications due to their suitable magnetic properties, high Curie temperature, high resistance, low dielectric losses and relatively cheap production. In various applications, it is necessary to use different parameters of ferrites, which can be achieved in several ways. One of the ways to change the magnetic properties ferrites, is a change in the proportions of the starting materials during the production of the sample. In our case, the ratio of nickel to zinc was the same for all the samples examined, namely $0.42 : 0.58$. Only the lanthanum content was changed. As a trivalent element, it belongs to the group of rare earths and, when entering the crystal lattice, occupies the positions of trivalent iron ions. Rare earths including lanthanum play an important role in influencing magnetic properties such as electrical resistance and power losses. They also play an important role in determining magnetocrystalline anisotropy. We varied the lanthanum content for values $x = 0, 0.02, 0.04, 0.06, 0.08$ and $0.1$, which appear in the formula Ni$_{0.48}$Zn$_{0.52}$La$_{x}$Fe$_{2-x}$O$_{4}$. The next options that affect the properties of ferrites are the methods of sample production, different firing temperatures and also the firing time. Our samples were produced by glycine-nitrate process based on auto-combustion preparation method and subsequently sintered at different temperatures ($T$ = $400$, $550$, $700$, $850$, $1000$, $1100$, $1200$, $1300$°C), all for $6$ hours. One sample was not sintered at all and is therefore a sample after decomposition. We evaluated the samples using a total of five methods. To determine the structural parameters, we used X-ray diffraction together with SEM micrographs. The magnetic properties of ferrites were measured using thermomagnetic analysis methods and hysteresis loop measurements. In addition, to analyze the use of the investigated ferrites as magnetic fillers in polymer composites, we used the results of measuring the frequency dependences of the complex permeability. The ferrite filler content in all investigated composites was $60$ vol.$\%$ percent and epoxy resin was used as the polymer matrix.
Acknowledgements
This work was supported by the Scientific Grant Agency of the Ministry of Education, Science, Research and Sport of the Slovak Republic (VEGA), under project no. 1/0041/24.
