Journal of Nanoparticle Research

, Volume 13, Issue 10, pp 4583–4590 | Cite as

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
Research Paper

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/O2 partial pressures (0–0.015). The exchange-bias properties appear to be insensitive to the amount of O2 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 O2. 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 O2 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.

Keywords

Exchange bias Magnetic nanoparticles Cluster source Nanocomposite 

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Copyright information

© Springer Science+Business Media B.V. 2011

Authors and Affiliations

  • J. A. De Toro
    • 1
  • J. P. Andrés
    • 1
  • J. A. González
    • 1
  • J. M. Riveiro
    • 1
  • M. Estrader
    • 2
  • A. López–Ortega
    • 2
  • I. Tsiaoussis
    • 3
  • N. Frangis
    • 3
  • J. Nogués
    • 2
    • 4
  1. 1.Instituto Regional de Investigación Científica Aplicada (IRICA) and Departamento de Física AplicadaUniversidad de Castilla-La ManchaCiudad RealSpain
  2. 2.CIN2(ICN-CSIC) and Universitat Autònoma de BarcelonaCatalan Institute of NanotechnologyBarcelonaSpain
  3. 3.Solid State Physics Section, Department of PhysicsAristotle University of ThessalonikiThessalonikiGreece
  4. 4.Institució Catalana de Recerca i Estudis Avançats (ICREA)BarcelonaSpain

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