resumo
Surface mediated phenomena are important in controlling the magnetism of nanocrystals. Here, we provide a versatile chemical method which allows the formation of EuS nanocrystals encapsulated in poly(styrene) (PS). These materials are the first example of a polymer based EuS nanocomposite prepared in situ. Besides their practical interest, these materials are of general relevance because they allow fundamental knowledge on the magnetism of EuS, which is commonly used as a model of an insulating ferromagnet, to be acquired. Comparatively to the starting powders of EuS nanocrystals (8 nm), in the final nanocomposites there is a decrease of the blocking temperature TB and a change in the shape of the field-cooled susceptibility curve, indicating that the intensity of dipolar interactions decreases when the nanoparticles are incorporated into PS. Differences in the magnetic properties of the EuS nanocrystals and the EuS/PS nanocomposites are also due to the appearance of a peak in the susceptibility at 60 K, in the latter sample, ascribed to surface phenomena occurring in EuS nanocrystals dispersed in the polymer matrix.
palavras-chave
SINGLE-MOLECULE PRECURSORS; RADICAL POLYMERIZATION; MINIEMULSION POLYMERIZATION; CARBON NANOTUBES; LATEX-PARTICLES; QUANTUM DOTS; CDE E; NANOPARTICLES; ROUTE; NANOMATERIALS
categoria
Chemistry; Materials Science
autores
Pereira, AS; Rauwel, P; Reis, MS; Silva, NJO; Barros-Timmons, A; Trindade, T
nossos autores
Ana Margarida Madeira Viegas de Barros Timmons
Professor associado
Angela Sofia dos Santos Pereira
Bolseiro de pós-Doutoramento
Nuno João Silva
Investigador Principal
Tito Trindade
Professor Catedráticoagradecimentos
A. S. Pereira thanks Fundacao para a Ciencia e Tecnologia (FCT) for a PhD grant. N. J. O. Silva acknowledges CSIC for a I3P contract. This work was funded by FCT and FEDER (project PTDC/QUI/67712/2006). The work in Zaragoza has been supported by the research grants MAT2007-61621 and CSD2007-00010 from the Ministry of Education. We thank Dr A. Lopes (U. Aveiro) for some of the TEM analysis.