Magnetic Systems with Carbon Nanotubes

We report on mesoscopic magnetic devices and structures realized on the basis of multiwalled Carbon nanotubes. The nanotubes serve either as conducting lines between ferromagnetic terminals or as a container for ferromagnetic nanowires. Spin‐conserving transport through the nanotubes can be established over distances of several 100 nm and gives rise to large magnetotransport effects with resistance changes between 30% and 60% at 4.2 K. CVD growth of multiwall Carbon nanotubes in the presence of a suitable metallorganic agent containing Fe, Co, or Ni results in a filling of the tubes with nanocrystalline metallic wires which are found to behave ferromagnetically even at room temperature.