Estrader Marta, López-Ortega Alberto, Golosovsky Igor V, Estradé Sònia, Roca Alejandro G, Salazar-Alvarez German, López-Conesa Lluís, Tobia Dina, Winkler Elin, Ardisson José D, Macedo Waldemar A A, Morphis Andreas, Vasilakaki Marianna, Trohidou Kalliopi N, Gukasov Arsen, Mirebeau Isabelle, Makarova O L, Zysler Roberto D, Peiró Francesca, Baró Maria Dolors, Bergström Lennart, Nogués Josep
Departament de Química Inorgànica, Universitat de Barcelona, Diagonal 645, E-08028, Barcelona, Spain.
Nanoscale. 2015 Feb 21;7(7):3002-15. doi: 10.1039/c4nr06351a.
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.
过渡金属氧化物中化学计量与物理化学性质之间的密切关系使其成为具有可调谐性的材料而备受关注。当涉及到纳米结构时，这些特性会更加突出。然而，由于纳米级材料的复杂性，建立结构形态与功能之间的明确关系往往很复杂。在这方面，在FexO/Fe3O4体系中，已经观察到磁性能存在很大程度上无法解释的广泛分散现象。在此，我们通过全面的多技术方法表明，在大尺寸（45纳米）和小尺寸（9纳米）的FexO/Fe3O4核壳纳米颗粒中，磁结构性质之间存在明确的相关性，这可以解释磁行为的分散情况。结果表明，大尺寸纳米颗粒中的FexO核是反铁磁性的，具有类似体相的化学计量和晶胞参数，而小尺寸颗粒中的FexO核则是高度非化学计量且应变的，没有明显的反铁磁性。这些结果突出了充分表征对于全面理解纳米结构金属氧化物性质的重要性。
