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Pàgina inicial > Articles > Articles publicats > Crossover from individual to collective magnetism in dense nanoparticle systems : |
Data: | 2022 |
Resum: | 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 (E) to nanoparticle anisotropy (KV, 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 K 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 KV/E ≈ 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 T(interacting)/T(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. |
Ajuts: | European Commission 731976 European Commission 101046909 Agencia Estatal de Investigación PID2019-106229RB-I00 Ministerio de Ciencia e Innovación SEV-2017-0706 Ministerio de Economía y Competitividad MAT2015-65295-R Ministerio de Educación, Cultura y Deporte BEAGAL18/00095 Agència de Gestió d'Ajuts Universitaris i de Recerca 2017/SGR-292 |
Nota: | Altres ajuts: ICN2 is funded by the CERCA program/Generalitat de Catalunya |
Drets: | Aquest document està subjecte a una llicència d'ús Creative Commons. Es permet la reproducció total o parcial, la distribució, la comunicació pública de l'obra i la creació d'obres derivades, fins i tot amb finalitats comercials, sempre i quan es reconegui l'autoria de l'obra original. |
Llengua: | Anglès |
Document: | Article ; recerca ; Versió publicada |
Matèria: | Dipolar interactions ; Magnetic anisotropy ; Magnetic nanoparticles ; Superspin glass |
Publicat a: | Small, Vol. 18, issue 28 (July 2022) , art. 2106762, ISSN 1613-6829 |
11 p, 2.5 MB |