This study was supported by the Spanish Ministerio de Ciencia e Innovación under projects MAT2005-05524-C02-02, MAT-2007-66181, MAT2008-06765-C02, MAT2008-06517-C02-01, CSD2007-00041 (NANOSELECT), CSD2008-00023 (FUNCOAT), CSD2009-00013, and the European Commission NMP3-SL-2008-214107. Consejo Superior de Investigaciones Científicas and the Spanish Ministerio de Ciencia e Innovación are thanked for financial support. Jordi Llobet from the Instituto de Microelectrónica de Barcelona IMB-CNM-CSIC and Xavier Borrisé from the Centro de Investigación en Nanociencia y Nanotecnología, Bellaterra, Barcelona, CIN2-CSIC are thanked for the preparation of the cross-sectional samples. TEM study has been carried out at the LABMET, Red de Laboratorios de la Comunidad de Madrid. http://dx.doi.org/10.1007/s11051-011-0518-5

We present a morphological, structural, and magnetic characterization of Co nanoparticles (mean diameter of 10.3 ± 1.8 nm) grown using a gas aggregation source and embedded in a silicon oxide matrix by sequential deposition of nanoparticles and silicon oxide. We show that the Co nanoparticles >soft-land> on the substrates and suffer a moderate oxidation in contact with the silicon oxide. Despite this moderate oxidation, it is found that, at room temperature, the magnetic volume of the resulting nanoparticles is below the superparamagnetic limit. The results presented in this article are compatible with the presence of an assembly of magnetically independent particles that also display a moderate exchange bias at low temperature. © 2011 Springer Science+Business Media B.V.

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