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Particle size-dependent superspin glass behavior in random compacts of monodisperse maghemite nanoparticles
Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Industriell teknik.
Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Fasta tillståndets fysik.
Univ Castilla La Mancha, IRICA, E-13071 Ciudad Real, Spain.;Univ Castilla La Mancha, Dept Fis Aplicada, E-13071 Ciudad Real, Spain..
Inst Bioengn & Nanotechnol, 31 Biopolis Way, Singapore 138669, Singapore..
Vise andre og tillknytning
2016 (engelsk)Inngår i: MATERIALS RESEARCH EXPRESS, ISSN 2053-1591, Vol. 3, nr 4, artikkel-id 045015Artikkel i tidsskrift (Fagfellevurdert) Published
Resurstyp
Text
Abstract [en]

Dense random assemblies made from highly monodisperse gamma-Fe2O3 nanoparticles with sizes ranging from 6.2 to 11.5 nm have been investigated by DC and AC magnetometry. It is found that all assemblies undergo superspin glass phase transitions. The superspin glass phase transition temperature is strongly dependent on the particle size and the nature of the interparticle interaction. However the transition from superparamagnet to superspin glass, as evidenced by the shape of the ac-susceptibility curves and the dynamic critical exponents associated with the transition, is similar in all systems.

sted, utgiver, år, opplag, sider
2016. Vol. 3, nr 4, artikkel-id 045015
Emneord [en]
magnetic nanoparticles, maghemite, superspin glass, phase transition
HSV kategori
Identifikatorer
URN: urn:nbn:se:uu:diva-299615DOI: 10.1088/2053-1591/3/4/045015ISI: 000377811500016OAI: oai:DiVA.org:uu-299615DiVA, id: diva2:949844
Forskningsfinansiär
Swedish Research CouncilGöran Gustafsson Foundation for promotion of scientific research at Uppala University and Royal Institute of TechnologyTilgjengelig fra: 2016-07-25 Laget: 2016-07-25 Sist oppdatert: 2017-04-07bibliografisk kontrollert
Inngår i avhandling
1. Interacting Magnetic Nanosystems: An Experimental Study Of Superspin Glasses
Åpne denne publikasjonen i ny fane eller vindu >>Interacting Magnetic Nanosystems: An Experimental Study Of Superspin Glasses
2017 (engelsk)Doktoravhandling, med artikler (Annet vitenskapelig)
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.

sted, utgiver, år, opplag, sider
Uppsala: Acta Universitatis Upsaliensis, 2017. s. 74
Serie
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1651-6214 ; 1505
Emneord
spin glass, SQUID magnetometry, maghemite, magnetism, nanoparticles
HSV kategori
Identifikatorer
urn:nbn:se:uu:diva-319717 (URN)978-91-554-9893-1 (ISBN)
Disputas
2017-06-02, Siegbahnsalen, Ångströmlaboratoriet, Lägerhyddsvägen 1, Uppsala, 13:15 (engelsk)
Opponent
Veileder
Tilgjengelig fra: 2017-05-10 Laget: 2017-04-07 Sist oppdatert: 2017-05-16

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