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.
CHARGE-DISTRIBUTION
SPIN DISORDER
SUPERPARAMAGNETISM
COFE2O4
REMANENCE
DYNAMICS
NANOCRYSTAL SUPERLATTICES
MAGNETORESISTANCE
RANDOM ANISOTROPY
MODEL
Author
Elena H. Sanchez
University of Castilla, La Mancha
Marianna Vasilakaki
Institut Catala de Nanociencia i Nanotecnologia
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 Cagliari
University of Castilla, La Mancha
Mikael Andersson
Chalmers, Chemistry and Chemical Engineering, Energy and Material
Uppsala University
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
Institut Catala de Nanociencia i Nanotecnologia
Josep Nogues
Spanish National Research Council (CSIC)
Catalan Institution for Research and Advanced Studies
Jose A. De Toro
University of Castilla, La Mancha
Chemistry of Materials
0897-4756 (ISSN) 1520-5002 (eISSN)
Vol. 32 3 969-981Subject Categories (SSIF 2011)
Inorganic Chemistry
Physical Chemistry
Condensed Matter Physics
DOI
10.1021/acs.chemmater.9b03268