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Remanence plots as a probe of spin disorder in magnetic nanoparticles
De Toro, José A. (Instituto Regional de Investigación Científica Aplicada)
Vasilakaki, Marianna (Ethniko Kentro Ereunas Physikōn Epistēmōn "Demokritos")
Lee, Su Seong (Institute of Bioengineering and Nanotechnology)
Andersson, Mikael S. (Uppsala University. Department of Engineering Sciences)
Normile, Peter S. (Instituto Regional de Investigación Científica Aplicada)
Yaacoub, Nader (Université du Maine. Institut des Molécules et Mateŕiaux du Mans)
Murray, Peyton D. (University of California. Physics Department)
Sánchez, Elena H. (Instituto Regional de Investigación Científica Aplicada)
Muñiz, Pablo (Instituto Regional de Investigación Científica Aplicada)
Peddis, Davide (Istituto di Struttura della Materia)
Mathieu, Roland (Uppsala University. Department of Engineering Sciences)
Liu, Kai (University of California. Physics Department)
Geshev, Julian (Universidade Federal Do Rio Grande Do sul. Instituto de Física)
Trohidou, Kalliopi N. (Ethniko Kentro Ereunas Physikōn Epistēmōn "Demokritos")
Nogués, Josep (Institut Català de Nanociència i Nanotecnologia)

Date: 2017
Abstract: Remanence magnetization plots (e. g. , Henkel or δM plots) have been extensively used as a straightforward way to determine the presence and intensity of dipolar and exchange interactions in assemblies of magnetic nanoparticles or single domain grains. Their evaluation is particularly important in functional materials whose performance is strongly affected by the intensity of interparticle interactions, such as patterned recording media and nanostructured permanent magnets, as well as in applications such as hyperthermia and magnetic resonance imaging. Here, we demonstrate that δM plots may be misleading when the nanoparticles do not have a homogeneous internal magnetic configuration. Substantial dips in the M plots of γ-FeO nanoparticles isolated by thick SiO shells indicate the presence of demagnetizing interactions, usually identified as dipolar interactions. Our results, however, demonstrate that it is the inhomogeneous spin structure of the nanoparticles, as most clearly evidenced by Mössbauer measurements, that has a pronounced effect on the δM plots, leading to features remarkably similar to those produced by dipolar interactions. X-ray diffraction results combined with magnetic characterization indicate that this inhomogeneity is due to the presence of surface structural (and spin) disorder. Monte Carlo simulations unambiguously corroborate the critical role of the internal magnetic structure in the δM plots. Our findings constitute a cautionary tale on the widespread use of remanence plots to assess interparticle interactions as well as offer new perspectives in the use of Henkel and δM plots to quantify the rather elusive inhomogeneous magnetization states in nanoparticles.
Grants: MINECO/MAT2015-65295-R
Rights: Tots els drets reservats.
Language: Anglès
Document: Article ; recerca ; Versió sotmesa a revisió
Subject: Cautionary tales ; Dipolar interaction ; Inhomogeneities ; Inter-particle interaction ; Magnetic characterization ; Magnetic configuration ; Magnetic nano-particles ; Recording media
Published in: Chemistry of materials, Vol. 29, Issue 19 (October 2017) , p. 8258-8268, ISSN 1520-5002

DOI: 10.1021/acs.chemmater.7b02522

39 p, 934.4 KB

The record appears in these collections:
Research literature > UAB research groups literature > Research Centres and Groups (research output) > Experimental sciences > Catalan Institute of Nanoscience and Nanotechnology (ICN2)
Articles > Research articles
Articles > Published articles

 Record created 2019-12-20, last modified 2021-08-01

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