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Volume 181, 2015
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Changing the magnetic properties of microstructure by directing the self-assembly of superparamagnetic nanoparticles

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Abstract

Magnetic nanoparticles (MNPs) in a liquid dispersion can be organized through controlled self-assembly by applying an external magnetic field that regulates inter-particle interactions. Thus, micro- and nanostructures of desired morphology and superlattice geometry that show emergent magnetic properties can be fabricated. We describe how superferromagnetism, which is a specific type of emergence, can be produced. Here, superparamagnetic nanoparticles that show no individual residual magnetization are organized into structures with substantial residual magnetization that behave as miniature permanent magnets. We investigate the emergence of superferromagnetism in an idealized system consisting of two MNPs, by considering the influence that interparticle magnetostatic interactions have on the dynamics of the magnetic moments. We use this model to illustrate the design principles for self-assembly in terms of the choice of material and MNP particle size. We simulate the dynamics of the interacting magnetic moments by applying the stochastic Landau–Lifshitz–Gilbert equation to verify our principles. The findings enable a method to pattern material magnetization with submicron resolution, a useful feature that has potential applications for magnetic recording and microfluidic particle traps. The analysis also yields useful empirical generalizations that could facilitate other theoretical developments.

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Publication details

The article was received on 02 Dec 2014, accepted on 16 Dec 2014 and first published on 17 Dec 2014


Article type: Paper
DOI: 10.1039/C4FD00245H
Author version available: Download Author version (PDF)
Citation: Faraday Discuss., 2015,181, 423-435
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    Changing the magnetic properties of microstructure by directing the self-assembly of superparamagnetic nanoparticles

    S. Ghosh and I. K. Puri, Faraday Discuss., 2015, 181, 423
    DOI: 10.1039/C4FD00245H

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