Facile synthetic route to nanosized ferrites by using mesoporous silica as a hard template

Spinel ferrite nanoparticles ( AFe(2)O(4); A = Mn, Ni, Cu, Co) of around 10 - 20 nm have been successfully synthesized via a simple nanocasting route using metal nitrates as precursors and mesoporous silica gel as a hard template. Spinel nanoparticles were formed under a nitrogen atmosphere by the high-temperature decomposition of a mixture of metal nitrates that fill the silica pores. The decomposition reactions occurred in the confined space provided by the mesopores of the silica template. Under these conditions, the silica walls restricted the growth of the oxide particles formed and so nanosized particles were obtained. The incorporation of different cations into the spinel ferrite enabled us to easily modulate the magnetic properties of the nanomaterials prepared by the template method. Depending on the chemical composition and temperature, we were able to obtain samples that display reversible magnetic behaviour ( zero coercivity field) and samples with coercivity values as high as 1.3 T ( 13 000 Oe).