Effect of rare earth substitution on magnetic and structural properties of Co1−xREx Fe2O4 (RE: Nd, Eu) nanoparticles prepared via EDTA/EG assisted sol–gel synthesis

Abstract

Four groups of the series of rare earth (RE) substituted cobalt ferrite Co1−x REx Fe2 O4; x = 0–0.2 in steps of 0.05 and RE is Nd and Eu were prepared using the sol–gel method at annealing temperatures 550° C. The materials were characterized by powder X-ray Diffraction (XRD), Field Emission Scanning Electron Microscopes (FESEM) and Fourier Transform Infrared spectroscopy (FTIR). The phase identification of the materials by XRD reveals the single-phase nature of the materials. The crystallite sizes of the materials were varied by altering the substitution content within the range of a minimum of 11 nm–31 nm. The magnetic parameters have been studied by using vibrating sample magnetometer (VSM). The saturation magnetization of the ferrite materials at room temperature decreases with the reduction of size. This has been attributed to increased surface to volume ratio and spin canting phenomena. The substituted rare-earth ions inhibit the grain growth of the materials in a systematic manner compared with that of the pure cobalt ferrite materials. There is an improvement in coercivities of the rare earth substituted cobalt ferrite especially for 5% Neodymium substituted cobalt ferrite with approximately 2 kOe coercive field. This is attributed to the contribution from the single ion anisotropy of the rare-earth ions present in the crystal lattice and the effects of a change in magnetic structures on the surface of the nanoparticles.