Direct fabrication of ferrite MFe₂O₄ (M = Zn, Mg)/Fe composite thin films by soft solution processing

Spinel ferrite/metal composite thin films of MFe₂O₄/Fe (M = Zn, Mg) with controlled grain sizes and shape were directly fabricated by a soft solution-processing route that involved the liquid-solid interfacial hydrothermal reaction of an Fe substrate with metal ions M²⁺ (M = Zn, Mg) in ammonia solution at lower temperatures (<200 °C). The grain particles of ZnFe₂O₄/Fe composite thin films show a well-developed octahedral shape with highly {111} preferential orientation, whereas the grain particles of MgFe₂O₄/Fe thin films displayed spherical shape. The saturation magnetization of the ferrite/Fe composites thin films was found to be much improved compared with that of single-phase ferrite products, and the ferrite/Fe thin films displayed superparamagnetism. The present soft-solution processing route will be extended to fabricate other novel ceramic/metal composite thin films.