Nano-magnetic ferrites with composition Mg_1-xZn_xFe₂O₄ (x = 0.3, 0.4, 0.5, 0.6, and 0.7) have been prepared by coprecipitation method. X-ray diffraction (XRD) studies showed that the lattice parameter was found to increase from 8.402 to 8.424 Å with Zn²⁺ ion content from 0.3 to 0.7. Fourier transform infrared (FTIR) spectra revealed two prominent peaks corresponding to tetrahedral and octahedral at around 560 and 430 cm^-1 respectively that confirmed the spinel phase of the samples. Transmission electron microscopy (TEM) images showed that the particle size was noted to increase from 18 to 24 nm with an increase in Zn content from x = 0.3 to 0.7. The magnetic properties were studied by vibrating sample magnetometer (VSM) and electron paramagnetic resonance (EPR) which ascertained the superparamagnetic behavior of the samples and contribution of superexchange interactions. The maximum magnetization was found to vary from 23.80 to 32.78 emu/g that increased till x = 0.5 and decreased thereafter. Further, X-ray photoelectron spectroscopy (XPS) was employed to investigate the chemical composition and substantiate their oxidation states.

In this paper, effect of Gd³⁺ was investigated on structural, magnetic, and dielectric properties of Mn_0.5Zn_0.5Gd_xFe_2–xO₄ (x = 0, 0.025, 0.050, 0.075, and 0.1) nanoparticles prepared by facile coprecipitation method. X-ray diffraction (XRD) studies confirmed the single cubic spinel phase for all the samples and showed that lattice parameter (a_exp) was found to increase from 8.414 to 8.446 Å with the substitution of Gd³⁺ ions due to their larger ionic radii than the replaced Fe³⁺ ions. Shape and size of developed nanoparticles were studied using transmission electron microscopy (TEM) and found that particle size decreased from 31.06 to 21.12 nm for x = 0–0.1. Magnetic properties showed that maximum magnetization decreased from 39.21 to 23.59 emu/g, and Curie temperature decreased from 192 to 176 ℃ with increase in x from 0 to 0.1 due to weakening of superexchange interaction. Dielectric parameters like dielectric constant ( ${\epsilon }^{\prime }$and ${\epsilon }^{″}$), dielectric loss (tanδ), AC conductivity (σ_ac), and impedance ( $Z^{\prime }$and $Z^{″}$) as a function of frequency and composition were analyzed and discussed. It was found that ${\epsilon }^{\prime }$, ${\epsilon }^{″}$, σ_ac, and tanδ values decreased with Gd substitution, which has been explained based on Maxwell–Wagner theory and hopping mechanism of electrons between Fe³⁺ and Fe²⁺ ions at octahedral sites. Nyquist plots for all the developed compositions showed single semi-circular arc which indicate the dominant effect of grain boundaries.