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Title

Exchange-bias and superparamagnetic behaviour of Fe nanoparticles embedded in a porous carbon matrix

AuthorsFernández, M. P.; Schmool, D. S.; Silva, A. S.; Sevilla Solís, Marta CSIC ORCID ; Fuertes Arias, Antonio Benito CSIC ORCID ; Gorria, P.; Blanco, J. A.
KeywordsX-ray diffraction
Magnetic properties
Mossbauer effect and spectroscopy
STEM/TEM
Powders
Nanoparticles
Carbon-based and nanotubes
Issue Date22-Oct-2008
PublisherElsevier
CitationJournal of Non-Crystalline Solids 354(47/51): 5219-5221 (2008)
AbstractCombining different experimental techniques, the physical properties of Fe nanoparticles (NPs) randomly dispersed in a porous carbon have been investigated. From the analysis of TEM images and the broad maximum observed in ZFC–FC magnetization measurements under an applied magnetic field of 2.5 mT, a broad-size distribution NPs (5–50 nm) is estimated. The nature of these NPs (α-Fe and γ-Fe) was determined from X-ray diffraction. Furthermore, magnetization measurements suggest that these Fe-NPs remain completely blocked below 60 K due to a magnetic exchange-bias coupling induced on the surface of these NPs. However, the true nature of the core–shell responsible for this exchange bias within the NPs, is not totally understood yet. In addition, the system begins to be magnetically unblocked above 60 K, becoming almost superparamagnetic above 200 K. Room temperature Mössbauer spectroscopy confirms the existence of both α- and γ-Fe phases; an additional quadrupole component is required to properly fit the spectrum, which could be associated with the NP’s shell or to an oxide phase probably located on the surface of the NPs.
Description3 pages, 3 figures, 1 table. -- Printed version published 1 Dec 2008. -- Issue title: Non-Crystalline Solids 9, 9th International Workshop on Non-Crystalline Solids (Porto, Portugal, 27-30 April 2008)
Publisher version (URL)http://dx.doi.org/10.1016/j.jnoncrysol.2008.06.116
URIhttp://hdl.handle.net/10261/11561
DOI10.1016/j.jnoncrysol.2008.06.116
ISSN0022-3093
Appears in Collections:(INCAR) Artículos

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