Structural, thermomagnetic, and dielectric properties of Mn0.5Zn0.5GdxFe2-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 Mn0.5Zn0.5GdxFe2-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 A 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 degrees C with increase in x from 0 to 0.1 due to weakening of superexchange interaction. Dielectric parameters like dielectric constant (epsilon ' and epsilon ''), dielectric loss (tan delta), AC conductivity (sigma(ac)), and impedance (Z ' and Z '') as a function of frequency and composition were analyzed and discussed. It was found that epsilon ', epsilon '', sigma(ac), and tan delta 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.