The effect of Mn2+ substitution on magnetic properties of MnxFe3−xO4 nanoparticles prepared by coprecipitation method

Abstract

In this work single phase Mn substituted magnetite (MnxFe3−xO4, x=0–0.75) nanoparticles were prepared by the coprecipitation method. X-ray diffraction analysis showed that the prepared nanoparticles have a single-phase spinel structure. An average crystallite size of about 20nm has been obtained for all the samples, using Scherrer's formula. Field emission scanning electron microscope images of the samples showed that the average particle sizes were about 25nm. The Curie temperature (TC) of the samples were measured by a Faraday balance and decreased from 610°C to 510°C by increasing Mn content from x=0 to x=0.75. The M–H curves of the nanoparticles exhibited superparamagnetic behavior for all the samples except for x=0 and saturation magnetization (σs) decreased with increasing of Mn content. The temperature dependence of AC-susceptibility of samples at different frequencies reveals maxima corresponding to the different blocking temperatures. It was shown that the frequency dependence of the blocking temperature can be described by the Vogel–Fulcher law for superparamagnets, well.