Investigation of magnetic properties of Al substituted nickel ferrite nanopowders, synthesized by the solgel method

Abstract

NiFe2-xAlxO4 nanopowders, where x is from 0 to 1.5 with a step of 0.5, have been synthesized by the solgel method and the effect of non-magnetic aluminum content on their structural and magnetic properties were investigated. The X-ray diffraction (XRD) patterns revealed that the synthesized nanopowders are single phase with a spinel structure. Mean crystallite sizes of the samples were calculated by Scherrers formula and were in the range 2031 nm. The morphology of the nanopowders was investigated by TEM and the mean particle sizes of the samples were in the range 5580 nm. Magnetic hysteresis loops were recorded at room temperature in a maximum applied field of 3000 Oe. The results show that by increasing the aluminum content, the magnetizations of the nanopowders are decreased. This reduction is caused by non-magnetic Al3 ions, which by their substitutions the super exchange interactions between different sites will be reduced. It is also seen that the magnetizations of the nanopowders are lower than those related to their bulk counterparts. This reduction was found to be as a consequence of surface spin disorder. MT curves of the samples were obtained using a Faraday balance and by which the Curie temperatures of the powders were determined. The results that are obtained show that the Curie temperatures of the nanopowders are higher than those of their bulk counterparts. © 2011 Elsevier B.V. All rights reserved.