Role of the oxygen partial pressure in the formation of composite Co-CoO nanoparticles by reactive aggregation

J. A. De Toro, J. P. Andrés, J. A. González, J. M. Riveiro, M. Estrader, A. López–Ortega, I. Tsiaoussis, N. Frangis, J. Nogués

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7 Citations (Scopus)

Abstract

The magnetic properties of diluted films composed of nanocomposite Co-CoO nanoparticles (of ∼8 nm diameter) dispersed in a Cu matrix have been investigated. The nanoparticles were formed in an aggregation chamber by sputtering at different Ar/O 2 partial pressures (0-0.015). The exchange-bias properties appear to be insensitive to the amount of O 2 during their formation. However, the temperature dependence of the magnetization, M(T), exhibits two different contributions with relative intensities that correlate with the amount of O 2 . The magnetic results imply that two types of particles are formed, nanocomposite Co-CoO (determining the exchange-bias) and pure CoO, as confirmed by transmission electron microscopy observations. Importantly, as the O 2 partial pressure during the sputtering is raised the number of nanocomposite Co-CoO nanoparticles (exhibiting exchange-bias properties) is reduced and, consequently, there is an increase in the relative amount of pure, antiferromagnetic CoO particles. © 2011 Springer Science+Business Media B.V.
Original languageEnglish
Pages (from-to)4583-4590
JournalJournal of Nanoparticle Research
Volume13
Issue number10
DOIs
Publication statusPublished - 1 Jan 2011

Keywords

  • Cluster source
  • Exchange bias
  • Magnetic nanoparticles
  • Nanocomposite

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