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Interacting Magneti...
Interacting Magnetic Nanosystems : An Experimental Study Of Superspin Glasses
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- Andersson, Mikael Svante (författare)
- Uppsala universitet,Fasta tillståndets fysik
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- Mathieu, Roland, Docent (preses)
- Uppsala universitet,Fasta tillståndets fysik
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- Fiorani, Dino (opponent)
- Istituto di Struttura della Materia, Italy
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(creator_code:org_t)
- ISBN 9789155498931
- Uppsala : Acta Universitatis Upsaliensis, 2017
- Engelska 74 s.
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Serie: Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, 1651-6214 ; 1505
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Abstract
Ämnesord
Stäng
- 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.
Ämnesord
- NATURVETENSKAP -- Fysik -- Den kondenserade materiens fysik (hsv//swe)
- NATURAL SCIENCES -- Physical Sciences -- Condensed Matter Physics (hsv//eng)
Nyckelord
- spin glass
- SQUID magnetometry
- maghemite
- magnetism
- nanoparticles
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