Magnetic and structural properties of nanosize Ni–Zn–Cr ferrite particles synthesized by combustion reaction

This paper reports on Cr3+-doped and undoped Ni–Zn nanosize ferrite obtained by reaction combustion synthesis. The powders resulting from this synthesis were characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM), and their magnetic properties examined with an alternative gradient magnetometer (AGM) and by ferromagnetic resonance (FMR). The XRD results confirmed the formation of Ni0.5Zn0.5Fe2O4 bulk spinel and small quantities of second phase hematite (αFe2O4) to the powders without chromium. However, the powders containing 0.1 mol of chromium showed only a Ni–Zn ferrite cubic phase. The Ni0.5Zn0.5Fe2O4 and Ni0.5Zn0.5Fe1.9Cr0.1O4 showed average crystallite sizes of 20.7 and 22.7 nm, respectively. The SEM micrographs of the powders to the sample without chromium reveals nanoparticles with a regular morphology without pre-sintering and with the presence of soft agglomerations. The powder with 0.1 mol of chromium displays homogeneous and finer nanoparticles, which are more reactive and hence more agglomerated. Saturation magnetization of the phase without Cr3+ was 61.97 emu/g, while that of the powder with chromium was 40.56 emu/g. The inclusion of chromium caused the magnetization index to drop by 34% and decreased the coercive field, Hc, by 77%. It is known that the inclusion of chromium is advantageous for high-frequency transformer applications.