Chemical synthesis and magnetic investigations on Cr3+ substituted Zn-ferrite superparamagnetic nano-particles

In present report, we have discussed the effect of Cr3+ substitution on structural and magnetic properties of ZnFe2-xCrxO4 (x=0, 0.1, 0.3, 0.5) ferrite nano-particles synthesized by a chemical co-precipitation method using oleic acid as surfactant. Structural studies were carried out using X-ray diffraction (XRD) and transmission electron microscopy (TEM) techniques. XRD pattern of the prepared powder samples annealed at 350 degrees C confirmed the formation of single phase cubic spinel structure. TEM images confirmed the nano size formation of particles. A Vibrating Sample Magnetometer (VSM) has been employed to probe the change in magnetic properties with change in composition. Magnetic particle size (D-m) calculated from hysteresis loop was found less than the particle size (D-T) calculated from TEM micrograph due to spin canting effect. The magnetization studies inferred that magnetic moment (eta(B)) showed decreasing trend with increase in Cr3+ substitution, its value decreases from 0.548 (for x=0.0) to 0.125 (for x=0.5). The saturation magnetization (M-s) value was found to decrease from 12.76 emu/gm (for x=0.0) to 2.92 emu/gm (for x=0.5). The coercivity (H-c) was found to change proportionally with the particle sizes of investigated ferrites. Squareness (S) values revealed that particles interact by magnetostatic interactions. The M-H loop of all the samples is narrow with low value of coercivity and retentivity; indicate the superparamagnetic nature of these samples. (C) 2014 Elsevier Ltd and Techna Group S.r.l. All rights reserved.