Form, Content, and Magnetism in Iron Oxide Nanocrystals

Chalasani, Rajesh and Vasudevan, Sukumaran (2011) Form, Content, and Magnetism in Iron Oxide Nanocrystals. In: Journal of Physical Chemistry, 115 (37). pp. 18088-18093.

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Abstract

Monodisperse iron oxide nanocrystals with spherical and cubic morphologies, of comparable dimensions, have been prepared by the thermal decomposition of FeOOH. The lattice spacings of both forms agree with that of magnetite, Fe(3)O(4). The two, however, exhibit very different blocking temperatures. Nanocrystals of cubic morphology are superparamagnetic above 190 K while the spherical nanocrystals at a lower temperature, 142 K. The higher blocking temperatures in particles of cubic morphology are shown to be a consequence of exchange bias fields. We show that in the present iron oxide nanocrystals the exchange bias fields originate from the presence of trace amounts of wustite, FeO. A Reitveld refinement analysis of the X-ray diffraction patterns shows that nanocrystals of cubic morphology have a higher FeO content. The higher FeO content is responsible for the larger exchange bias fields that in turn lead to a higher blocking temperature for nanocrystals with cubic morphology.

Item Type:	Journal Article
Publication:	Journal of Physical Chemistry
Publisher:	American Chemical Society
Additional Information:	Copyright of this article belongs to American Chemical Society.
Department/Centre:	Division of Chemical Sciences > Inorganic & Physical Chemistry
Date Deposited:	11 Oct 2011 09:40
Last Modified:	11 Oct 2011 09:40
URI:	http://eprints.iisc.ac.in/id/eprint/41301

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