Effects of thermal treatments on the microstructure and magnetic properties of spinel NiFe2O4-silica nanocomposites

The effects of thermal treatments on the microstructure and magnetic proper ties of NiFe2O4-silica nanocomposites were investigated in this paper. The samples with matrices of silica and mullite gels were prepared by sol-gel p rocesses at different calcination temperatures. The interactions between th e magnetic nanocrystals and the matrices as well as the coordination state changes during the crystallization were revealed by Mossbauer spectroscopy. The results show that the sorts and the relative content of the matrix gel s strongly affect the structural evolution of the nickel spinel from amorph ous state to nanocrystallites.