Effects of the individual particle relaxation time on superspin glass dynamics

The low temperature dynamic magnetic properties of two dense magnetic nanoparticle assemblies with similar superspin glass transition temperatures T sub()g~ 140 K are compared. The two samples are made from batches of 6 and 8 nm monodisperse gamma -Fe sub(2) O sub(3) nanoparticles, respectively. The...

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Bibliographic Details
Published in:Physical review. B 2016-02, Vol.93 (5), Article 054407
Main Authors: Andersson, Mikael Svante, De Toro, Jose Angel, Lee, Su Seong, Normile, Peter S., Nordblad, Per, Mathieu, Roland
Format: Article
Language:English
Subjects:
Anisotropy
Assemblies
Barriers
Condensed matter
Dynamics
Magnetic properties
Nanostructure
Relaxation time
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Summary:The low temperature dynamic magnetic properties of two dense magnetic nanoparticle assemblies with similar superspin glass transition temperatures T sub()g~ 140 K are compared. The two samples are made from batches of 6 and 8 nm monodisperse gamma -Fe sub(2) O sub(3) nanoparticles, respectively. The properties of the individual particles are extracted from measurements on reference samples where the particles have been covered with a thick silica coating. The blocking temperatures of these dilute assemblies are found at 12.5 K for the 6 nm particles and at 35 K for the 8 nm particles, which implies different anisotropy energy barriers of the individual particles and vastly different temperature evolution of their relaxation times. The results of the measurements on the concentrated particle assemblies suggest a strong influence of the particle energy barrier on the details of the aging dynamics, memory behavior, and apparent superspin dimensionality of the particles.
ISSN:2469-9950
2469-9969
DOI:10.1103/PhysRevB.93.054407