Preparation of pure and Mn-substituted magnetite nanoparticles and investigation of their magnetic properties

In this work magnetite (Fe3O4) and Mn substituted ones (MnxFe(1-x)Fe2O4, x=0.25, 0.5 0.75) have been prepared via coprecipitation method. XRD investigations of the samples show that all the samples are single phase and have a spinel structure. Using ScherrerYs formula the mean crystallite sizes of the samples were calculated and were in the range of 10 nm. It was found that room temperature magnetization of the nanosized samples are smaller than those of their bulk counterpatrts. This decrease has been explained according to the core-shell model. Magnetization of the samples were decreased with increasing x, which has been discussed according to site occupation of the substituted Mn 2+ ions. We have determined the Curie temperature Tc of Fe3O4 nanoparticles.Increase in Curie temperature of nanoparticles with respecttobulkones is describe by the finite-size-scaling formula. A superparamagnetic behaviour was found in Mn substituted magnetite with x=0.5 and x=0.75.

کلیدواژه ها:

magnetization ، coprecipitation ، spin canting ، spin glass ، core-shell model