Spin disorder and magnetic anisotropy in Fe3O4 nanoparticles

By E. Lima, A. L. Brandl, A. D. Arelaro, G. Goya. 2005

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We have studied the magnetic behavior of dextran-coated magnetite (Fe3O4) nanoparticles with median particle size ⟨d⟩=8nm. Magnetization curves and in-field Mossbauer spectroscopy measurements showed that the magnetic moment MS of the particles was much smaller than the bulk material. However, we found no evidence of magnetic irreversibility or nonsaturating behavior at high fields, usually associated to spin canting. The values of magnetic anisotropy Keff from different techniques indicate that surface or shape contributions are negligible. It is proposed that these particles have bulklike ferromagnetic structure with ordered A and B sublattices, but nearly compensated the magnetic moments. The dependence of the blocking temperature with frequency and applied fields, TB(H,ω), suggests that the observed nonmonotonic behavior is governed by the strength of interparticle interactions.

Subfields: Atomic and Molecular Physics, and Optics, Materials Chemistry, Renewable Energy, Sustainability and the Environment

View Paper: https://www.semanticscholar.org/paper/f7a207482bf9b63b0da1e301d945e73495bb3a5a