화학공학소재연구정보센터
Current Applied Physics, Vol.15, No.3, 226-231, 2015
Mossbauer spectroscopy studies of the magnetic properties of ferrite nanoparticles
Studies of the ferrite nanoparticles prepared by the chemical decomposition of iron chlorides with a various ratio xi = Fe3+/Fe2+ are herein presented. The microstructure and the magnetic properties have been studied by transmission electron microscopy (TEM), X-ray diffraction (XRD) and Mossbauer spectroscopy (MS). The TEM studies show that the nanoparticles have almost a spherical shape with the diameter of (12 +/- 2) nm for all samples. The measured XRD pattern was mainly composed of lines which were indexed with a cubic spinel structure. The analysis of the Mossbauer data shows that the microstructure of the nanoparticles consists of the core formed by nonstoichiometric magnetite and maghemite shell. A small amount of hematite, probably on the surface of the nanoparticles with xi = 1.75, 2.0, was detected. At temperatures T <= 150 K the spin canting of surface maghemite with xi = 2.25 was observed while for the samples with xi = 1.75, 2.0 such effect was suppressed by the presence of hematite on the surface of the nanoparticles. Infield Mossbauer spectra with xi = 1.75, 2.0 show that magnetic moments of the magnetite/maghemite core are parallel while magnetic moments of the surface hematite are perpendicular to the direction of the external magnetic field. (C) 2014 Elsevier B.V. All rights reserved.