New aspects about the growth of metal-filled CNT on structured substrates and the tuning of their magnetic properties

Nanostructured magnetic materials such as arrays of nanowires and filled nanotubes exhibit unique and tuneable magnetic properties e.g. the anomalous high coercivity, which make them favourable for applications in high density magnetic recording media.
We show effective CVD-routes for the defined growth of ensembles as well as individuals of metall-filled carbon nanotubes (Fe, Co, Ni) on structured silicon substrates and alumina substrates. The filled nanotubes were obtained due to continuous decomposition (thermic or plasma) of metal-containing precursors or hydrocarbons at 750-850°C. The nanotube dimensions can be controlled by the size of the catalyst on the substrate and with the reaction conditions. Further we report about a homogeneous embedding procedure of the CNT ensembles in a solid matrix. After the mechanical treatment the remaining nanotube stubs are analyzed with the magnetometer. In addition detailed investigations with transmission electron microscopy (TEM), atomic force microscopy (AFM) and Moessbauer spectroscopy give new insightes in the growth of filled carbon nanotubes.