Dipolar Magnetism in Ordered and Disordered Low-Dimensional Nanoparticle Assemblies

Varón, M. and Beleggia, M. and Kasama, T. and Harrison, R. J. and Dunin-Borkowski, R. E. and Puntes, V. F. and Frandsen, C. (2013) Dipolar Magnetism in Ordered and Disordered Low-Dimensional Nanoparticle Assemblies. Scientific Reports, 3 (1234). ISSN 2045-2322, ESSN: 2045-2322 DOI https://doi.org/10.1038/srep01234

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Abstract

Magnetostatic (dipolar) interactions between nanoparticles promise to open new ways to design nanocrystalline magnetic materials and devices if the collective magnetic properties can be controlled at the nanoparticle level. Magnetic dipolar interactions are sufficiently strong to sustain magnetic order at ambient temperature in assemblies of closely-spaced nanoparticles with magnetic moments of ≥ 100 μB. Here we use electron holography with sub-particle resolution to reveal the correlation between particle arrangement and magnetic order in self-assembled 1D and quasi-2D arrangements of 15 nm cobalt nanoparticles. In the initial states, we observe dipolar ferromagnetism, antiferromagnetism and local flux closure, depending on the particle arrangement. Surprisingly, after magnetic saturation, measurements and numerical simulations show that overall ferromagnetic order exists in the present nanoparticle assemblies even when their arrangement is completely disordered. Such direct quantification of the correlation between topological and magnetic order is essential for the technological exploitation of magnetic quasi-2D nanoparticle assemblies.

Item Type:	Article
Uncontrolled Keywords:	2013AREP; IA65;
Subjects:	03 - Mineral Sciences
Divisions:	03 - Mineral Sciences 08 - Green Open Access
Journal or Publication Title:	Scientific Reports
Volume:	3
Identification Number:	https://doi.org/10.1038/srep01234
Depositing User:	Sarah Humbert
Date Deposited:	25 Feb 2013 16:33
Last Modified:	01 May 2014 22:06
URI:	http://eprints.esc.cam.ac.uk/id/eprint/2684

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