Effect of rare earth elements on the structural, magnetic and electrical behavior of Ni-Zn-Cr nanoferrites

Mixed nickel-zinc-chromium ferrites having the general formula Ni0.7Zn0.3CrxRyFe2-x-yO4 (where x = 0.5, y = 0.02 and R = Gd3+, Sm3+ and Ce3+) were prepared, for the first time by using auto-combustion method at low sintering temperature (523 K). X-ray diffraction (XRD) analysis and Fourier transform infrared spectrum (FT-IR) confirmed the formation of single phase spinel structure in all the samples. The variations of the lattice parameter and particle size were discussed in the view of ionic radii. High resolution transition electron microscope (HT-TEM) and scan electron microscopy (SEM) images showed spherical and elongated shapes of the nanoparticles where the average particle size ranged 13-17 nm. The vibrating sample magnetometer (VSM) measurements confirmed a strong influence of rare earth doping on the saturation magnetization (Ms) and coercivity (Hc) due to the preferential occupation of RE ions in the octahedral B-sites. The magnetic parameters suggested that these nano-materials are suitable for technological application. The dielectric parameters (ε׳, ε″ and tanδ) and electrical conductivity (σ) were measured at different temperatures in the frequency range (102-105Hz). The electrical conductivity of the sample ferrite doped with Gd was showing semi-conducting behavior while for the samples doped with Ce and Sm, semi-conductor to semi-metallic were observed. The dielectric loss (tanδ) and dielectric constant (ɛ) show that these materials are useful in high frequency applications.