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

Abstract 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 °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 (Dm) calculated from hysteresis loop was found less than the particle size (DT) calculated from TEM micrograph due to spin canting effect. The magnetization studies inferred that magnetic moment (ηB) 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 (MS) 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 (Hc) 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.