Microstructural and Magnetic Investigations of Wustite-Spinel Core-Shell Cubic-Shaped Nanoparticles

作者：Pichon Benoit P^*; Gerber Olivier; Lefevre Christophe; Florea Ileana; Fleutot Solenne; Baaziz Walid; Pauly Matthias; Ohlmann Maxime; Ulhaq Corinne; Ersen Ovidiu; Pierron Bohnes Veronique; Panissod Pierre; Drillon Marc; Begin Colin Sylvie

来源：Chemistry of Materials, 2011, 23(11): 2886-2900.

DOI：10.1021/cm2003319

• iron oxide nanoparticles
• cubic-shaped nanoparticles
• core-shell nanoparticles
• oxidation mechanisms
• magnetic properties
• exchange bias coupling
• electron tomography
• electron holography

Most studies on the synthesis of nanoparticles are currently focused on the controlled synthesis of new morphologies, including core-shell structures, which are expected to exhibit new magnetic properties for uses in spintronics and recording media applications. In this study, the structure, morphology, and composition of cubic-shaped nanoparticles are carefully investigated and compared to those of spherically shaped nanoparticles through the use of a combination of techniques: X-ray diffraction (XRD) and transmission electronic microscopy (TEM) combined with more sensitive techniques such as scanning transmission electron microscopy-high-angle annular dark field (STEM-HAADF) imaging, electron tomography, and holography. While spherically shaped nanoparticles (NPs) crystallize with the spinel structure, cubic-shaped NPs can be described as a cubic core of wustite surrounded by a spine! shell. Stresses are observed at the core-shell interface and within the spinel shell due to the epitaxial growth and oxidation mechanisms of the wustite phase. Furthermore, magnetic measurements displayed an exchange bias coupling between the antiferromagnetic (AFM) core and the ferrimagnetic (FIM) shell structure of cubic-shaped nanoparticles. It is shown that the magnetic properties are influenced by stresses generated by the oxidation of wustite and, also exhibit variations depending upon the evolution of this core-shell structure as a function of the oxidation time.

• 出版日期2011-6-14