Magnetic diphase nanostructure of ZnFe2O4/γ-Fe2O3

Magnetic diphase nanostructures of ZnFe2O4/gamma-Fe2O3 were synthesized by a solvothermal method. The formation reactions were optimized by tuning the initial molar ratios of Fe/Zn. All samples were characterized by X-ray diffraction, thermogravimetric analysis, infrared spectroscopy, and Raman spectra. It is found that when the initial molar ratio of Fe/Zn is larger than 2, a diphase magnetic natiostructure of ZnFe2O4/gamma-Fe2O3 was formed, in which the presence of ZnFe2O4 enhanced the thermal stability of gamma-Fe2O3. Further increasing the initial molar ratio of Fe/Zn larger than 6 destabilized the diphase nanostructure and yielded traces of secondary phase alpha-Fe2O3. The grain surfaces of diphase nanostructure exhibited a spin-glass-like structure. At room temperature, all diphase nanostructures are superparamagnetic with saturation magnetization being increased with gamma-Fe2O3 content. (c) 2007 Elsevier Inc. All rights reserved.