Simultaneous individual and dipolar collective properties in binary assemblies of magnetic nanoparticles
Sánchez, Elena H. (Universidad de Castilla-La Mancha. Instituto Regional de Investigacion Cientifica Aplicada)
Vasilakaki, Marianna (Institute of Nanoscience and Nanotechnology (Atenes, Grècia))
Lee, Su Seong (Institute of Bioengineering and Nanotechnology (Singapore))
Normile, Peter S. (Universidad de Castilla-La Mancha. Departamento de Física Aplicada)
Muscas, Giuseppe (Universita degli Studi di Cagliari. Dipartimento di Fisica)
Murgia, Massimiliano (Universidad de Castilla-La Mancha. Departamento de Física Aplicada)
Andersson, Mikael S. (Uppsala University. Department of Engineering Sciences)
Singh, Gurvinder (University of Sydney. School of Aerospace, Mechanical and Mechatronic Engineering)
Mathieu, Roland (Uppsala University. Department of Engineering Sciences)
Nordblad, Per (Uppsala University. Department of Engineering Sciences)
Ricci, Pier Carlo (Universita degli Studi di Cagliari. Dipartimento di Fisica)
Peddis, Davide (Universita degli Studi di Genova. Dipartimento di Chimica e Chimica Industriale)
Trohidou, Kalliopi N. (Institute of Nanoscience and Nanotechnology (Atenes, Grècia))
Nogués, Josep (Institut Català de Nanociència i Nanotecnologia)
De Toro, José A. (Universidad de Castilla-La Mancha. Departamento de Física Aplicada)

Data:	2020
Resum:	Applications based on aggregates of magnetic nanoparticles are becoming increasingly widespread, ranging from hyperthermia to magnetic recording. However, although some uses require collective behavior, others need a more individual-like response, the conditions leading to either of these behaviors are still poorly understood. Here, we use nanoscale-uniform binary random dense mixtures with different proportions of oxide magnetic nanoparticles with low/high anisotropy as a valuable tool to explore the crossover from individual to collective behavior. Two different anisotropy scenarios have been studied in two series of binary compacts: M1, comprising maghemite (γ-Fe2O3) nanoparticles of different sizes (9. 0 nm/11. 5 nm) with barely a factor of 2 between their anisotropy energies, and M2, mixing equally sized pure maghemite (low-anisotropy) and Co-doped maghemite (high-anisotropy) nanoparticles with a large difference in anisotropy energy (ratio > 8). Interestingly, while the M1 series exhibits collective behavior typical of strongly coupled dipolar systems, the M2 series presents a more complex scenario where different magnetic properties resemble either "individual-like"or "collective", crucially emphasizing that the collective character must be ascribed to specific properties and not to the system as a whole. The strong differences between the two series offer new insight (systematically ratified by simulations) into the subtle interplay between dipolar interactions, local anisotropy and sample heterogeneity to determine the behavior of dense assemblies of magnetic nanoparticles.
Ajuts:	European Commission 731976 Ministerio de Economía y Competitividad SEV-2017-0706 Ministerio de Economía y Competitividad MAT2016-77391-R Ministerio de Economía y Competitividad MAT2015-65295-R Agència de Gestió d'Ajuts Universitaris i de Recerca 2017/SGR-292
Nota:	Altres ajuts: ICN2 is funded by the CERCA Programme/Generalitat de Catalunya.
Drets:	Tots els drets reservats.
Llengua:	Anglès
Document:	Article ; recerca ; Versió sotmesa a revisió
Matèria:	Anisotropy energies ; Collective behavior ; Collective properties ; Different proportions ; Dipolar interaction ; Dipolar systems ; High anisotropy ; Specific properties
Publicat a:	Chemistry of materials, Vol. 32, issue 3 (Feb. 2020) , p. 969-981, ISSN 1520-5002

DOI: 10.1021/acs.chemmater.9b03268

Preprint 64 p, 2.9 MB

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