Modeling the Brownian relaxation of nanoparticle ferrofluids: Comparison with experiment. Issue 2 (18th January 2013)

• Record Type: Journal Article
• Authors: Martens, Michael A.; Deissler, Robert J.; Wu, Yong; Bauer, Lisa; Yao, Zhen; Brown, Robert; Griswold, Mark
• Is Part Of: Medical physics. Volume 40:Issue 2(2013)
• Page Start: n/a
• Page End: n/a
• Publication Date: 2013-01-18
• Subjects: Nanotechnologies‐applications -- Dynamics of magnetic nanoparticles -- Fine‐particle systems; nanocrystalline materials -- Biophysical mechanisms of interaction; biomagnetism -- biomedical materials -- Brownian motion -- Fokker‐Planck equation -- Legendre polynomials -- magnetic fluids -- magnetic moments -- magnetic particles -- nanomagnetics; nanotechnologies‐applications -- Brownian motion -- ferrofluids (magnetohydrodynamics) -- Fokker‐Planck equation statistical physics -- Langevin method -- dynamics of magnetic nanoparticles; Nano‐structures -- Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties -- Of magnetic liquids, e.g. ferrofluids; Langevin equation -- Hydrodynamics -- Nanoparticles -- Magnetic moments -- Iron -- Ferrofluids -- Viscosity -- Magnetic nanoparticles -- Ferromagnetism -- Magnetic fields; Medical physics -- Periodicals; Medical physics; Geneeskunde; Natuurkunde; Toepassingen; Biophysics; Periodicals; Periodicals; Electronic journals; 610.153
• DOI: 10.1118/1.4773869
• Languages: English
• ISSNs: 0094-2405

Abstract

Abstract : Purpose: : The authors investigate the ability of current models for magnetic nanoparticles immersed in dilute ferrofluids and external sinusoidal magnetic fields to explain recent experiments in which the relaxation effects are dominated by viscous damping. Methods: : The Fokker–Planck (FP) equation appropriate for the nanoparticle magnetic moment distribution corresponding to the underlying stochastic Langevin model is numerically studied and solutions compared to experimental results. The FP equation is solved using an expansion in Legendre polynomials. The polydisperse properties of the ferrofluids are incorporated into the analysis. Results: : By using a FP approach that includes polydispersion, the authors obtain good agreement with recent experimental results using ferrofluids containing nanoparticles with average hydrodynamic diameters in the 40–120 nm range. Conclusions: : For nanoparticles used in recent magnetic spectroscopy experiments, the FP approach can be used to accurately model experimental data in the situation where Brownian relaxation effects are dominant and the ferrofluids are dilute.