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Origin of the large dispersion of magnetic properties in nanostructured oxides: Fe x O/Fe 3 O 4 nanoparticles as a case study

2014; Royal Society of Chemistry; Volume: 7; Issue: 7 Linguagem: Inglês

10.1039/c4nr06351a

2040-3372

Marta Estrader, Alberto López‐Ortega, I. V. Golosovsky, Sònia Estradé, Alejandro G. Roca, Germán Salazar-Álvarez, Lluís López‐Conesa, Dina Tobia, E. Winkler, José D. Ardisson, W. A. A. Macedo, Andreas Morphis, Marianna Vasilakaki, K. N. Trohidou, Arsen Gukasov, I. Mirebeau, O. L. Makarova, Roberto D. Zysler, F. Peiró, M.D. Baró, Lennart Bergström, J. Nogués,

Multiferroics and related materials

The intimate relationship between stoichiometry and physicochemical properties in transition-metal oxides makes them appealing as tunable materials. These features become exacerbated when dealing with nanostructures. However, due to the complexity of nanoscale materials, establishing a distinct relationship between structure-morphology and functionalities is often complicated. In this regard, in the FexO/Fe3O4 system a largely unexplained broad dispersion of magnetic properties has been observed. Here we show, thanks to a comprehensive multi-technique approach, a clear correlation between the magneto-structural properties in large (45 nm) and small (9 nm) FexO/Fe3O4 core/shell nanoparticles that can explain the spread of magnetic behaviors. The results reveal that while the FexO core in the large nanoparticles is antiferromagnetic and has bulk-like stoichiometry and unit-cell parameters, the FexO core in the small particles is highly non-stoichiometric and strained, displaying no significant antiferromagnetism. These results highlight the importance of ample characterization to fully understand the properties of nanostructured metal oxides.