Simultaneous Individual and Dipolar Collective Properties in Binary Assemblies of Magnetic Nanoparticles
Journal article, 2020

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 (gamma-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.












Elena H. Sanchez

University of Castilla, La Mancha

Marianna Vasilakaki

Catalan Institute of Nanoscience and Nanotechnology (ICN2)

Su Seong Lee

Inst Bioengn & Nanotechnol

Peter S. Normile

University of Castilla, La Mancha

Giuseppe Muscas

Uppsala University

University of Cagliari

Massimiliano Murgia

University of Castilla, La Mancha

University of Cagliari

Mikael Andersson

Uppsala University

Chalmers, Chemistry and Chemical Engineering, Energy and Material

Gurvinder Singh

The University of Sydney

Roland Mathieu

Uppsala University

Per Nordblad

Uppsala University

Pier Carlo Ricci

University of Cagliari

Davide Peddis

University of Genoa

National Research Council of Italy (CNR)

Kalliopi N. Trohidou

Catalan Institute of Nanoscience and Nanotechnology (ICN2)

Josep Nogues

Catalan Institution for Research and Advanced Studies

Spanish National Research Council (CSIC)

Jose A. De Toro

University of Castilla, La Mancha

Chemistry of Materials

0897-4756 (ISSN) 1520-5002 (eISSN)

Vol. 32 3 969-981

Subject Categories

Inorganic Chemistry

Physical Chemistry

Condensed Matter Physics



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