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Spin Disorder and Magnetic Anisotropy in Fe3O4 Nanoparticles

E. Lima Jr.·A. L. Brandl·A. D. Arelaro·G. F. Goya
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Abstract

We have studied the magnetic behavior of dextran-coated magnetite (Fe$_3$O$_4$) nanoparticles with median particle size $\left =8$ $nm$. Magnetization curves and in-field Mössbauer spectroscopy measurements showed that the magnetic moment $M_S$ of the particles was much smaller than the bulk material. However, we found no evidence of magnetic irreversibility or non-saturating behavior at high fields, usually associated to spin canting. The values of magnetic anisotropy $K_{eff}$ from different techniques indicate that surface or shape contributions are negligible. It is proposed that these particles have bulk-like ferrimagnetic structure with ordered A and B sublattices, but nearly compensated magnetic moments. The dependence of the blocking temperature with frequency and applied fields, $T_B(H,ω)$, suggests that the observed non-monotonic behavior is governed by the strength of interparticle interactions.

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E. Lima Jr., A. L. Brandl, A. D. Arelaro, G. F. Goya. 2006-05-26. Spin Disorder and Magnetic Anisotropy in Fe3O4 Nanoparticles. https://doi.org/10.1063/1.2191471

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