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Magnetic properties of nanoparticle compacts with controlled broadening of the particle size distribution
Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.ORCID iD: 0000-0002-5261-2047
Univ Castilla La Mancha, Spain.
Inst Bioengn & Nanotechnol, Singapore.
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2017 (English)In: Physical Review B, ISSN 2469-9950, E-ISSN 2469-9969, Vol. 95, no 18, 184431Article in journal (Refereed) Published
Abstract [en]

Binary random compacts with different proportions of small (volume V) and large (volume 2V) essentially bare maghemite nanoparticles are used to investigate the effect of controllably broadening the particle size distribution on the magnetic properties of magnetic nanoparticle assemblies with strong dipolar interaction. A series of eight random mixtures of highly uniform 9.0- and 11.5-nm-diameter maghemite particles prepared by thermal decomposition is studied. In spite of the severely broadened size distributions in the mixed samples, well-defined superspin glass transition temperatures are observed across the series, their values increasing linearly with the weight fraction of large particles.

Place, publisher, year, edition, pages
2017. Vol. 95, no 18, 184431
National Category
Engineering and Technology Condensed Matter Physics
Identifiers
URN: urn:nbn:se:uu:diva-319714DOI: 10.1103/PhysRevB.95.184431ISI: 000405203000010OAI: oai:DiVA.org:uu-319714DiVA: diva2:1087435
Funder
Swedish Research Council
Note

Title in List of papers in Thesis: Magnetic properties of nanoparticles compacts with controlled broadening of the particle size distribution

Available from: 2017-04-07 Created: 2017-04-07 Last updated: 2017-11-29Bibliographically approved
In thesis
1. Interacting Magnetic Nanosystems: An Experimental Study Of Superspin Glasses
Open this publication in new window or tab >>Interacting Magnetic Nanosystems: An Experimental Study Of Superspin Glasses
2017 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

This thesis presents experimental results on strongly interacting γ-Fe2O3 magnetic nanoparticles and their collective properties. The main findings are that very dense randomly packed (≈60%) γ-Fe2O3 nanoparticles form a replica of a spin glass. The magnetic properties of the nanoparticle system are in most regards the same as those of an atomic spin glass. The system is therefore proposed as a model superspin glass. In superspin glasses the interacting building blocks that form the collective state are single domain nanoparticles, superspins with a magnetic moment of about 10000 μB, which can be compared to the atomic magnetic moment in spin glasses of approximately 1 μB.  It was found that the relaxation time of the individual nanoparticles impacts the collective properties and governs the superspin dimensionality. Several dense compacts, each prepared with nanoparticles of a specific size, with diameters 6, 8, 9 and 11.5 nm, were studied. All the studied compacts were found to form a superspin glass state. Non-interacting reference samples, consisting of the same particles but coated with a silica shell, were synthesized to determine the single particle magnetic properties.  It was also found that the effects of the nanoparticle size distribution, which lead to a variation of the magnetic properties, can be mitigated by having strong enough interparticle interactions. The majority of the work was carried out using SQUID magnetometry.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2017. 74 p.
Series
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1651-6214 ; 1505
Keyword
spin glass, SQUID magnetometry, maghemite, magnetism, nanoparticles
National Category
Engineering and Technology Condensed Matter Physics
Identifiers
urn:nbn:se:uu:diva-319717 (URN)978-91-554-9893-1 (ISBN)
Public defence
2017-06-02, Siegbahnsalen, Ångströmlaboratoriet, Lägerhyddsvägen 1, Uppsala, 13:15 (English)
Opponent
Supervisors
Available from: 2017-05-10 Created: 2017-04-07 Last updated: 2017-05-16

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Andersson, Mikael SvanteMathieu, RolandNordblad, Per

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