Petit C, Wang Z L, Pileni M P
Laboratoire des Matériaux Mésoscopiques et Nanométriques, UMR CNRS 7070, Université Pierre et Marie Curie, 4 Place Jussieu, 75251 Paris Cedex, France.
J Phys Chem B. 2005 Aug 18;109(32):15309-16. doi: 10.1021/jp052487+.
Seven-nanometer cobalt nanocrystals are synthesized by colloidal chemistry. Gentle annealing induces a direct structural transition from a low crystalline state to the hexagonal close packed (hcp) phase without changing the size, size distribution, and the lauric acid passivating layer. The hcp structured nanocrystals can be easily redispersed in solvent for further application and processing. We found that the magnetization at saturation and the magnetic anisotropy are strongly modified through the annealing process. Monolayer self-assembly of the hcp cobalt nanocrystals is obtained, and due to the dipolar interaction, ferromagnetic behavior close to room temperature has been observed. This work demonstrates a novel approach for obtaining small size hcp structured cobalt magnetic nanocrystals for many technological applications.
通过胶体化学合成了七纳米钴纳米晶体。温和退火诱导了从低晶态到六方密堆积（hcp）相的直接结构转变，而不改变尺寸、尺寸分布和月桂酸钝化层。具有hcp结构的纳米晶体可以很容易地重新分散在溶剂中以进行进一步的应用和加工。我们发现，通过退火过程，饱和磁化强度和磁各向异性得到了强烈改变。获得了hcp钴纳米晶体的单层自组装，并且由于偶极相互作用，在接近室温时观察到了铁磁行为。这项工作展示了一种获得用于许多技术应用的小尺寸hcp结构钴磁性纳米晶体的新方法。
