Structural and magnetic properties of γ-Fe2O3 nanoparticles coated on silica spheres

The structural and magnetic properties of gamma-Fe2O3 nanoparticles dispersed on sol-gel silica spheres were investigated through XRD, TEM, Mossbauer (20, 80 and 300 K) and EPR (80, 300 K) measurements. The XRD spectra clearly indicated the formation of pure gamma-Fe2O3, nanoparticles and the absence of any other form of iron oxide. TEM images showed a uniform distribution of the nanoparticles of size similar to6 nm on the surfaces of silica spheres (diameter similar to35-60 nm). The low temperature (20 K) Mossbauer spectra consisted of a partially split sextet superimposed on a doublet. The partial magnetic splitting of the sextet at 20 K revealed the effect of surface magnetization and surface modifications of the gamma-Fe2O3 nanoparticles coated on silica spheres. The surface magnetization arising out of mis-aligned spins at the surface as evidenced by Mossbauer spectra was further confirmed by electron paramagnetic resonance (E00PR) studies.