Cr-substituted nanocrystalline Ni–Co ferrites: tuning dielectric, magnetic, structural, X-band microwave absorption, and characteristic properties

The structural, characteristic, dielectric, and magnetic features of Co0.5Ni0.5CrxFe2 − xO4 (0.0≤x≤1.0\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$0.0 \le x \le 1.0$$\end{document} with a step of 0.2 x-concentration) nanoparticles are prepared via the hydrothermal method. The investigation of characteristics, structural, and magnetic features of the produced nanoparticles are examined through XRD, FT-IR, SEM–EDS, TEM-SAED, and VSM, respectively. AC conductivity and the dielectric investigations are also reported. According to the XRD measurements, all samples have the M-type hexagonal crystal structure nanocrystallites of between 27 and 97 nm. Refined structural parameters using Rietveld analysis are carried out using the TOPAS refinement program. A good match was observed between the diffraction patterns obtained and calculated by Rietveld analysis. Moreover, the morphological analyses indicate that the relatively small spherical structures of Ni–Co ferrites particles can be seen to change from spherical to relatively oval-shaped with increasing chromium content. The results of the FT-IR study show that the spinel structure has formed as predicted because the expected range of absorption bands is present. According to magnetic measurements, Cr-substituted Ni–Co ferrite nanostructures reveal a relatively soft ferromagnetic property. The coercive field (Hc) variation has a propensity to decrease in relation to the Cr-concentration. The electromagnetic constitutive parameters are calculated from measured S-parameters (S11 and S21) using network analyzer and the return losses of the samples are then obtained to determine microwave absorption properties. According to the dielectric and magnetic tangent losses or dissipation factors, both dielectric and magnetic features can mutually reinforce in terms of microwave absorption properties in the X-band. The Cr2O3 impurity peaks obtained by XRD analysis have an effect on the microwave absorption properties. The results of the microwave absorption based on each concentration reveal that there exist electromagnetic wave absorptions between approximately 11 GHz and 12.4 GHz in the X-band. The absorption trend is also towards the Ku-band.