Microstructure and magnetism of nanoparticles with γ-Fe core surrounded by α-Fe and iron oxide shells
10 páginas, 8 figuras, 1 tabla.-- PACS number(s): 75.50.Bb, 75.50.Tt, 71.70.Gm, 75.20.-g
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2010-03
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dig-incar-es-10261-477872022-09-02T09:44:40Z Microstructure and magnetism of nanoparticles with γ-Fe core surrounded by α-Fe and iron oxide shells Fernández-García, Maria Paz Gorria, P. Blanco, J. A. Fuertes Arias, Antonio Benito Sevilla Solís, Marta Boada, R. Chaboy, Jesús Schmool, D. S. Grenèche, Jean Marc 10 páginas, 8 figuras, 1 tabla.-- PACS number(s): 75.50.Bb, 75.50.Tt, 71.70.Gm, 75.20.-g Iron-carbon nanocomposites have been elaborated by means of a simple chemical procedure based on in situ synthesis of iron nanoparticles within the nanopores of an activated carbon. The Fe nanoparticles present a broad particle-size distribution (5–40 nm). A combined structural and magnetic study seems to suggest that most of the nanoparticles of mean size ∼15 nm have exotic “onionlike” core-shell morphology of γ-Fe nucleus surrounded by a concentric double shell of α-Fe and maghemitelike oxide. The true nature of Fe-oxide was successfully evidenced through room temperature x-ray absorption spectroscopy. The whole system does not reach a fully superparamagnetic regime even at 750 K, probably due to higher blocking temperatures for the largest nanoparticles. Mössbauer spectrometry indicates that low temperature para-to-antiferromagnetic transition for the γ-Fe phase cannot be discarded. In addition, the external Fe-oxide shell exhibits spin-glass behavior giving rise to the freezing of its magnetic moments at low temperatures. Hence, we propose a competing double magnetic coupling: (i) the oxide shell/α-Fe interaction and (ii) the possible antiferromagnetic coupling between γ-Fe nucleus and α-Fe layer; as being both responsible for the observed exchange bias effect at T=5 K (Hex≈150 Oe). Financial support from FEDER and the Spanish MICINN (Grants No. MAT2008-00407 and No. MAT2008-06542-C04) is acknowledged. One of us, M.P.F.G, thanks MICINN for the award of a FPI grant cofinanced by the European Social Fund. Peer reviewed 2012-04-02T09:31:16Z 2012-04-02T09:31:16Z 2010-03 artículo http://purl.org/coar/resource_type/c_6501 Physical Review B 81(9): 094418 (2010) 1098-0121 http://hdl.handle.net/10261/47787 10.1103/PhysRevB.81.094418 1550-235X en http://dx.doi.org/10.1103/PhysRevB.81.094418 open American Physical Society |
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10 páginas, 8 figuras, 1 tabla.-- PACS number(s): 75.50.Bb, 75.50.Tt, 71.70.Gm, 75.20.-g |
| format |
artículo |
| author |
Fernández-García, Maria Paz Gorria, P. Blanco, J. A. Fuertes Arias, Antonio Benito Sevilla Solís, Marta Boada, R. Chaboy, Jesús Schmool, D. S. Grenèche, Jean Marc |
| spellingShingle |
Fernández-García, Maria Paz Gorria, P. Blanco, J. A. Fuertes Arias, Antonio Benito Sevilla Solís, Marta Boada, R. Chaboy, Jesús Schmool, D. S. Grenèche, Jean Marc Microstructure and magnetism of nanoparticles with γ-Fe core surrounded by α-Fe and iron oxide shells |
| author_facet |
Fernández-García, Maria Paz Gorria, P. Blanco, J. A. Fuertes Arias, Antonio Benito Sevilla Solís, Marta Boada, R. Chaboy, Jesús Schmool, D. S. Grenèche, Jean Marc |
| author_sort |
Fernández-García, Maria Paz |
| title |
Microstructure and magnetism of nanoparticles with γ-Fe core surrounded by α-Fe and iron oxide shells |
| title_short |
Microstructure and magnetism of nanoparticles with γ-Fe core surrounded by α-Fe and iron oxide shells |
| title_full |
Microstructure and magnetism of nanoparticles with γ-Fe core surrounded by α-Fe and iron oxide shells |
| title_fullStr |
Microstructure and magnetism of nanoparticles with γ-Fe core surrounded by α-Fe and iron oxide shells |
| title_full_unstemmed |
Microstructure and magnetism of nanoparticles with γ-Fe core surrounded by α-Fe and iron oxide shells |
| title_sort |
microstructure and magnetism of nanoparticles with γ-fe core surrounded by α-fe and iron oxide shells |
| publisher |
American Physical Society |
| publishDate |
2010-03 |
| url |
http://hdl.handle.net/10261/47787 |
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