VSM and Mossbauer study of nanostructured hematite

In the present work, we have synthesized nanostructured hematite samples using chemical precipitation method. The crystal structure and the grain size of the samples were studied using XRD. The zero field cooled and field cooled magnetization curves of the samples were recorded in the temperature range from 300 to 10 K. The variations of Morin transition temperature and blocking temperature with the grain size of the samples were investigated. The hysterics curves of the samples were recorded and the samples showed a superparamagnetic nature at room temperature where as, at 10 K the samples showed open hysteres is curves. The sample with smaller grain size showed higher value of coercivity compared to samples with larger grain size. Mossbauer spectra of the samples were recorded and the grain size dependence on Mossbauer parameters was investigated. (C) 2009 Elsevier B. V. All rights reserved.