Crossover From Individual to Collective Magnetism in Dense Nanoparticle Systems: Local Anisotropy Versus Dipolar Interactions
Artikel i vetenskaplig tidskrift, 2022
Dense systems of magnetic nanoparticles may exhibit dipolar collective behavior. However, two fundamental questions remain unsolved: i) whether the transition temperature may be affected by the particle anisotropy or it is essentially determined by the intensity of the interparticle dipolar interactions, and ii) what is the minimum ratio of dipole–dipole interaction (Edd) to nanoparticle anisotropy (KefV, anisotropy⋅volume) energies necessary to crossover from individual to collective behavior. A series of particle assemblies with similarly intense dipolar interactions but widely varying anisotropy is studied. The Kef is tuned through different degrees of cobalt-doping in maghemite nanoparticles, resulting in a variation of nearly an order of magnitude. All the bare particle compacts display collective behavior, except the one made with the highest anisotropy particles, which presents “marginal” features. Thus, a threshold of KefV/Edd ≈ 130 to suppress collective behavior is derived, in good agreement with Monte Carlo simulations. This translates into a crossover value of ≈1.7 for the easily accessible parameter TMAX(interacting)/TMAX(non-interacting) (ratio of the peak temperatures of the zero-field-cooled magnetization curves of interacting and dilute particle systems), which is successfully tested against the literature to predict the individual-like/collective behavior of any given interacting particle assembly comprising relatively uniform particles.
magnetic anisotropy
dipolar interactions
superspin glass
magnetic nanoparticles
Författare
Elena H. Sánchez
Universidad de Castilla, La Mancha
Marianna Vasilakaki
National Center for Scientific Research “Demokritos”
Su Seong Lee
Agency for Science, Technology and Research (A*STAR)
Peter S. Normile
Universidad de Castilla, La Mancha
Michael Andersson-Sarning
Chalmers, Kemi och kemiteknik, Kemiteknik
Uppsala universitet
R. Mathieu
Uppsala universitet
Alberto López-Ortega
Universidad Publica de Navarra
Universidad de Castilla, La Mancha
Benoit P. Pichon
Institut Universitaire de France
Université de Strasbourg
Davide Peddis
Consiglo Nazionale Delle Richerche
Università degli Studi di Genova
Chris Binns
Universidad de Castilla, La Mancha
P. Nordblad
Uppsala universitet
Kalliopi Trohidou
National Center for Scientific Research “Demokritos”
Josep Nogués
Institut Catala de Nanociencia i Nanotecnologia
Institucio Catalana de Recerca i Estudis Avancats
José A. De Toro
Universidad de Castilla, La Mancha
Small
1613-6810 (ISSN) 1613-6829 (eISSN)
Vol. 18 28 2106762Ämneskategorier
Fysikalisk kemi
Materialkemi
Den kondenserade materiens fysik
DOI
10.1002/smll.202106762
PubMed
35689307