Magnetic Interactions between Nanoparticles of Different Materials

  • Christopher W. Ostenfeld
  • Steen Mørup


Samples consisting of nanoparticles of α-Fe2O3 and mixtures of α-Fe2O3 and NiO or CoO have been studied by Mössbauer spectroscopy in the temperature range 20–320 K. Nanoparticles of α-Fe2O3, which normally do not have a Morin transition above 5 K, exhibited a Morin transition when mixed with NiO nanoparticles. Pure hematite particles, coated with oleic acid, showed a typical superparamagnetic behaviour at higher temperatures, whereas a sample of uncoated particles was less affected by relaxation, indicating a strong influence of inter-particle interactions. Admixture of NiO nanoparticles resulted in a smaller influence of inter-particle interactions on the spectra of uncoated particles. Admixture of CoO nanoparticles did not induce a Morin transition in α-Fe2O3 particles, but unlike NiO particles, CoO nanoparticles significantly slowed down the superparamagnetic relaxation.


Magnetic Anisotropy Mossbauer Spectrum Hematite Particle Quadrupole Shift Morin Transition 
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Copyright information

© Springer Science+Business Media Dordrecht 2002

Authors and Affiliations

  • Christopher W. Ostenfeld
    • 1
  • Steen Mørup
    • 1
  1. 1.Department of PhysicsTechnical University of DenmarkKgs. LyngbyDenmark

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