Preparation and magnetic properties of thin films containing mixtures of superparamagnetic nanocrystals encapsulated in amorphous metal oxides

Nanocomposite thin films consisting of 1: 1 mixtures of pre-formed CoFe2O4 and gamma g-Fe2O3 nanocrystals (NCs) encapsulated in amorphous aluminum oxide or titanium oxide have been prepared. The nanocrystals were prepared by the thermolysis of iron(III) acetylacetonate and cobalt(II) acetylacetonate in the presence of surfactants. The obtained NCs were codissolved in hexane solutions of either Al(OBu)(2)(EtOacac) or Ti((OPr)-Pr-i)(2)(acac)(2) and spin cast as thin films. Upon UV photolysis, the organic ligand was ejected from the film as volatile photoproducts, yielding amorphous metal oxide matrices which contain encapsulated nanocrystals. Zero-field cooled magnetization measurements confirm the presence of both nanocrystals, and show the presence of interparticle interactions. (c) 2006 Elsevier B.V. All rights reserved.