Manipulation of Magnetic Properties of Cr-Substituted Ni Ferrite Synthesized by Conventional Ceramic Technique

A series of polycrystalline Ni–Cr ferrites, with the composition NiCr xFe 2−xO4 (x = 0.0, 0.2, 0.4, 0.6, 0.8, and 1.0), were synthesized by conventional solid state ceramic method. The effect of Cr substitution on the structural, morphological, and magnetic properties of Ni ferrite has been investigated. Formation of single-phase cubic spinel structure of the compositions has been confirmed by X-ray diffraction. The morphological study was performed by scanning electron microscopy, and the average grain size was found to decrease with increasing Cr content. The magnetic properties of the samples were measured using an impedance analyzer and a vibrating sample magnetometer. Saturation magnetization, coercivity, and remanent magnetization have been measured from the hysteresis curves. The value of the saturation magnetization was found to decrease with increasing Cr concentration. The values of coercivity, remanent magnetization, and remanence ratio (Mr/Ms) ratio were also reported. The Curie temperatures (Tc) were determined from the plots of the real part of permeability (μi/\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$\mu _{\mathrm {i}}^{/}$\end{document}) versus temperature, and the values were found to be 511, 465, 415, 364, and 338 ∘C for x = 0.0, 0.2, 0.4, 0.6, and 0.8, respectively. The frequency dependence of the μi/\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$\mu _{\mathrm {i}}^{/}$\end{document}, loss factor, and quality factor has been studied as a function of composition in the frequency range 1 kHz–120 MHz. The real part of permeability was observed to be steady up to ∼10 MHz for all the samples. The loss factor (tan δ) of the samples decreased rapidly before 40 kHz and became almost constant with low values after 40 kHz. The values of quality factor have gradually been increased for samples with x ≤ 0.4, whilst the values diminished for samples with x ≥ 0.6.