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Comparative modeling of frequency mixing measurements of magnetic nanoparticles using micromagnetic simulations and Langevin theory

  • Dual frequency magnetic excitation of magnetic nanoparticles (MNP) enables enhanced biosensing applications. This was studied from an experimental and theoretical perspective: nonlinear sum-frequency components of MNP exposed to dual-frequency magnetic excitation were measured as a function of static magnetic offset field. The Langevin model in thermodynamic equilibrium was fitted to the experimental data to derive parameters of the lognormal core size distribution. These parameters were subsequently used as inputs for micromagnetic Monte-Carlo (MC)-simulations. From the hysteresis loops obtained from MC-simulations, sum-frequency components were numerically demodulated and compared with both experiment and Langevin model predictions. From the latter, we derived that approximately 90% of the frequency mixing magnetic response signal is generated by the largest 10% of MNP. We therefore suggest that small particles do not contribute to the frequency mixing signal, which is supported by MC-simulation results. Both theoretical approaches describe the experimental signal shapes well, but with notable differences between experiment and micromagnetic simulations. These deviations could result from Brownian relaxations which are, albeit experimentally inhibited, included in MC-simulation, or (yet unconsidered) cluster-effects of MNP, or inaccurately derived input for MC-simulations, because the largest particles dominate the experimental signal but concurrently do not fulfill the precondition of thermodynamic equilibrium required by Langevin theory.

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Metadaten
Author:Ulrich M. EngelmannORCiD, Ahmed Shalaby, Carolyn Shasha, Kannan M. Krishnan, Hans-Joachim KrauseORCiD
DOI:https://doi.org/10.3390/nano11051257
ISBN:2079-4991
Parent Title (English):Nanomaterials
Publisher:MDPI
Place of publication:Basel
Document Type:Article
Language:English
Year of Completion:2021
Date of the Publication (Server):2021/05/25
Tag:Frequency mixing magnetic detection; Langevin theory; Magnetic nanoparticles; Micromagnetic simulation; Nonequilibrium dynamics
Volume:11
Issue:5
First Page:1
Last Page:16
Note:
This article belongs to the Special Issue Applications and Properties of Magnetic Nanoparticles
Link:https://doi.org/10.3390/nano11051257
Zugriffsart:weltweit
Institutes:FH Aachen / Fachbereich Medizintechnik und Technomathematik
collections:Verlag / MDPI
Open Access / Gold
Licence (German):License LogoCreative Commons - Namensnennung