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Iron oxide and oxide-hydroxide nanoparticles in organic-inorganic matrices

AuthorsSilva, Nuno Joâo O.; Millán, Ángel CSIC ORCID ; Amaral, Vitor S.; Palacio, Fernando CSIC ORCID; Fu, Lianshe; Carlos, Luis D.; Zea Bermúdez, V. de
KeywordsIron oxides
Magnetic property
Organic-inorganic hybrid
Issue DateMay-2006
PublisherTrans Tech Publications
CitationMaterials Science Forum 514-516(1): 142-146 (2006)
AbstractNanometric ferrihydrite, maghemite and magnetite particles formed within an organicinorganic hybrid matrix were obtained by the sol-gel process. In contrast to precipitation techniques, sol-gel process appears as suitable way to achieve size-controlled nanoscopic magnetic particles anchored in a hybrid structure. The hybrid matrix here reported, named di-ureasil, is composed of poly(oxyethylene) chains grafted to siloxane groups by means of urea cross-linkages. The formation of ferrihydrite particles was achieved incorporating iron nitrate during the sol-gel process, at low pH. The formation of maghemite takes place after the incorporation of a mixture of Fe3+ and Fe2+ ions and treatment with an ammonia solution, after the sol-gel process. Magnetite nanoparticles are formed after the incorporation of Fe2+ ions and treatment with ammonia at 80ºC. The AC magnetic susceptibility shows thermal irreversibility with a blocking temperature TB≈13K and ≈25K depending on frequency for the ferrihydrite and maghemite particles, respectively. The magnetite nanoparticles are blocked at room temperature. Above the irreversibility the magnetization of ferrihydrite and maghemite follows a Langevin function modified with a linear term, as found in antiferromagnetic and ferrimagnetic particles.
Description5 pages.-- En: Advanced Materials Forum III.-- Edited by Paula Maria Vilarinho.
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