Spin transport in nanotubes (invited)

We study electron spin transport through carbon nanotubes contacted by ferr omagnetic electrodes. The resistance of a ferromagnetically contacted multi walled nanotube switches hysteretically as a function of applied magnetic f ield, with a maximum resistance change of 9% at 4.2 K. Magnetoresistance me asurements of carbon nanotubes having one cobalt contact and one platinum/g old contact, however, show no switching. In addition, we present calculatio ns of the magnetoresistance ratio for the ferromagnetic nanotube device, an d predict that a resistance change of 25% is possible. (C) 2001 American In stitute of Physics.