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Description of the magnetisation decay in ferrofluids with a narrow particle size distribution

D. Eberbeck - S. Hartwig - U. Steinhoff - L. Trahms

Physikalisch Technische Bundesanstalt Berlin, Fachlabor für Bioelektrizitat und Biomagnetismus, Berlin, Germany

The time decay of the magnetization of a system of magnetic nanoparticles (MNP) with uniaxial anisotropy was modeled by the superposition of the contribution of non­interacting moments of the particles with different sizes. Relaxation curves were modeled by the so called Moment Superposition Model (MSM) and then fitted with the well­ known modified logarithmic function Mr (t) = A ln(1 + tc /t). The goodness of fit decreases with narrowing of the energy barrier distribution. Also we have analyzed the experimental data by fitting with the modified logarithm and MSM. The particles have a broad energy barrier distribution (σ ≈ 0.5). Even in this case MSM shows slightly better results. The parameters of MSM have a clear physical meaning and could be determined by other measurements. We recommend the application of the MSM to analyze the relaxation curves of samples with a narrow particle size distribution. Figs 3, Refs 16.

Magnetohydrodynamics 39, No. 1, 77-83, 2003 [PDF, 0.17 Mb]

Copyright: Institute of Physics, University of Latvia
Electronic edition ISSN 1574-0579
Printed edition ISSN 0024-998X