Structure and magnetic properties of (Ni$_{1-x}$Zn$_{x}$)Fe$_{2}$O$_{4}$ ceramics with a spatial change in the composition

The samples of homogeneous ($x$ = 0; 0.1; 0.2) and multilayer ceramics with “oncoming” compositional gradient ($x$ = 0.2 $\to$ 0 $\to$ 0.2) based on solid solutions of nickel – zinc ferrites (Ni$_{1-x}$Zn$_{x}$)Fe$_{2}$O$_{4}$ have been prepared by thick-film technology. It was possible to ensure the synthesis of ceramics and to maintain inhomogeneous distribution of chemical elements throughout the thickness of the graded samples using the two-stage mode of heat treatment. Microstructure and crystal structure of the materials are studied. It is shown that the volume of the unit cell increases with increasing zinc content, while the grain size does not change significantly. The features of the magnetization of multilayer structures were investigated for two variants of application of external magnetic field (parallel and perpendicular to the sample plane). The resulting hysteresis loop for multilayer graded sample can be obtained by “summing up” the loops of homogeneous layers of the structure. No internal fields leading to a shift and distortion of the magnetic hysteresis loops were detected.