Formation of ordered cobalt nanowire arrays in the mesoporous silica channels*
Marina V. Chernysheva1, Nina A. Sapoletova1, Andrei A. Eliseev1, Alexey V. Lukashin1, Yuri D. Tretyakov1, and Peter Goernert2
1Department of Materials Science, Moscow State University, Moscow, 119992, Russia; 2INNOVENT, Prüssingstrasse 27 B, D-07745 Jena, Germany
Abstract: Here we report the synthesis and investigation of cobalt nanowire arrays using mesoporous silica as a host material. In the present work, a novel variant of synthesis of ordered magnetic nanowires in the mesoporous silica matrix was suggested. The method is based on incorporation of a hydrophobic metal compound Co2(CO)8 into the hydrophobic part of the silica-surfactant composite. The amount of cobalt intercalated into the mesoporous matrix was measured by chemical analysis (~5 wt %). Additional thermal modification was performed in order to provide a crystallization process of the cobalt nanowires. The prepared nanocomposites were characterized by X-ray diffraction (XRD), small-angle X-ray spectroscopy (SAXS), transmission electron microscopy (TEM), nitrogen capillary adsorption method (BET and BJH), and magnetic measurements. The anisotropy parameters of nanowires were determined using temperature dependence of magnetic susceptibility. For cobalt-containing sample annealed at 300 °C (form factor of nanowire higher than 16), the coercive force at room temperature was found to be 42.2 kA/m at saturation magnetization of 0.5 A.m2/kg, which is nearly sufficient for modern information recording media. According to TEM studies, cobalt particles are uniform and well ordered in the silica matrix. Thus, the suggested method leads to one-dimensional anisotropic nanostructures, which could find an application in high-density data storage devices.
Keywords: nanocomposites; magnetic nanowires; cobalt; mesoporous silica; anisotropy; ordered nanowire arrays; magnetic data storage.
*Paper based on a presentation at the 3rd IUPAC Workshop on New Directions in Chemistry - Workshop on Nanostructured Advanced Materials (WAM III), Stellenbosch, South Africa, 5-9 September 2005. Other presentations are published in this issue, pp. 1619-1801.