Structural, thermomagnetic, and dielectric properties of Mn_0.5Zn_0.5Gd_xFe_2–xO₄ (x = 0, 0.025, 0.050, 0.075, and 0.1)

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.