On the Fe 3O 4/Mn 1− xZn xFe 2O 4 core/shell magnetic nanoparticles

Abstract

Fe 3O 4 magnetic nanoparticles (NPs) were synthesized by the co-precipitation of Fe 3+ and Fe 2+ with ammonium hydroxide under hydrazine hydrate, and were characterized by X-ray powder diffraction (XRD), transmission electron microscopy (TEM) and vibrating sample magnetometer (VSM). In order to improve the particle dispersion, the bare Fe 3O 4 magnetic NPs were surface modified by sodium citrate under Ar protection. Mn–Zn ferrite NPs were prepared by co-precipitation. A group of orthogonal tests (L4 5) were arranged to investigate the effects of reaction temperature, and OH − and Fe 3+ concentrations on the magnetic property of Mn–Zn ferrite. It was found that the saturation magnetization increases evidently with the increasing reaction temperature. The effects of OH − and Fe 3+ concentrations on the magnetic property are minor. Mn–Zn ferrite NPs with high saturation magnetization (53 emu/g) were obtained. The XRD and element analysis for the Mn–Zn ferrite NPs indicates the particles are pure Mn 0.8Zn 0.2Fe 2O 4. Finally, Fe 3O 4/Mn 0.8Zn 0.2Fe 2O 4 core/shell nanocomposites were prepared by co-precipitation under the same condition. The core/shell nanocomposites obtained in the optimal condition demonstrate the highest saturation magnetization of 68 emu/g.