Magnetic properties of iron oxide-based nanoparticles: Study using Mössbauer spectroscopy with a high velocity resolution and magnetization measurements

Abstract We review the results of the study of magnetite, maghemite and nickel ferrite nanoparticles (NPs), applying for magnetic fluids, using Mossbauer spectroscopy with a high velocity resolution and magnetization measurements. The Mossbauer spectra of these NPs were fitted using a large number of magnetic sextets reflecting NPs complicity. The presence of polar molecules at the magnetite surface in magnetic fluid increases the NPs magnetic moment and the median hyperfine magnetic field. However, surface coating of maghemite NPs with dimeracptosuccinic acid decreases the median hyperfine magnetic field. An example of nickel ferrite NPs demonstrated a new physical model based on distribution of Ni 2+ in the local microenvironment of Fe 3+ which can explain a large number of magnetic sextets in the Mossbauer spectra measured with a high velocity resolution.