Regulated Ni-Zn-Co ferrites: structural, electrical and magnetic properties tailored by co doping

In this investigation, synthesized Co substituted Ni-Zn ferrites {Ni0.6Zn0.4-xCoxFe2O4 (for x = 0.00, 0.05, 0.10, 0.15, 0.20)} followed by double sintering method have been characterized by crystallographic, morphological, electrical and magnetic properties. X-ray diffraction (XRD) analysis as well as Fourier transform infrared (FT-IR) measurements of all the compositions verify the emergence of spinel cubic (single-phase) crystal structure. For Ni-Zn-Co ferrites, a cation dissemination has been suggested from the site occupancy preferences of different cations and its accuracy was confirmed by comparing the theoretically and experimentally computed lattice parameters as well as by measuring the magnetic moment. Scanning electron microscopy (SEM) showed diminished crystallite grains of average size 644 and 677 nm for 15% and 20% Co-doped compositions. An exceptional rise in dielectric constant for 10% Co-doped composite was observed at lower frequencies. AC conductivity of Co-doped ferrites showed that sigma(Lambda c) decreases with increased Co content. A single incomplete semicircle for all the investigated compositions is observed in the Nyquist plot. The impedance and modulus spectrums analysis confirmed that Co substituted samples attain non-Debye kind dielectric relaxation. The maximum relaxation time tau of 4.19 mu s was found for 20% Co-doped content. The 15% Co-doped composite exhibits a significant increment in saturation magnetization (87.39 emu/g) and in magnetic moment (3.69 mu mu B). The value of initial permeability decreases noticeably with increased Co addition. Magnetic loss (tan delta(M)) vs. frequency plot shows the beginning of relaxation peaks for all the NZCFO composites at higher (> 10(7) Hz) frequencies