Magnetic correlations in non-percolated Co-SiO2 granular films

Sandra Sankar, A. E. Berkowitz, D. Dender, J. A. Borchers, R. W. Erwin, S. R. Kline, David Smith

Research output: Contribution to journalConference articlepeer-review

76 Scopus citations


The zero-field-cooled state of Cox(SiO2)1-x granular films was investigated with small-angle neutron scattering, low-field AC magnetic susceptibility χ(T), and magnetoresistance measurements. Films with metallic volume fraction x = 0.41, which consist of 40 angstroms isolated particles that are superparamagnetic at room temperature, show an ordered magnetic state below 150 K consisting of 550 angstroms correlated regions that are aligned antiferromagnetically. The ordering is attributed to dipolar interactions. The temperature for the onset of correlated behavior, obtained from SANS (faster than 10-10 s), coincides with the frequency-independent maximum of χ′(T) for frequencies ranging from 0.1 to 1000 Hz. Furthermore, consistent with ferromagnetic correlations, the ZFC resistance is not the maximum resistance. Films with x = 0.32 exhibit evidence of magnetic interactions but no extended magnetic correlation - the magnetic correlation length corresponds to the particle size.

Original languageEnglish (US)
Pages (from-to)1-9
Number of pages9
JournalJournal of Magnetism and Magnetic Materials
Issue number1-2
StatePublished - Nov 2000
Event3rd Euroconference on Magnetic Properties of Fine Particles and their Relevance to Materials Science - Barceolona, Spain
Duration: Oct 19 1999Oct 22 1999

ASJC Scopus subject areas

  • Electronic, Optical and Magnetic Materials
  • Condensed Matter Physics


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