Magnetoresistance of ferromagnetically contacted carbon nanotubes

Magnetoresistance measurements of multi-walled carbon nanotubes having one or two ferromagnetic contacts are compared. Nanotubes with two cobalt conta cts show hysteretic switching in the magnetoresistance, with a maximum chan ge of 9% at 4.2 K, while nanotubes with one cobalt contact and one platinum /gold contact show no magnetoresistance switching. This provides further ev idence for coherent transport of electron spin through the multi-walled nan otube. In addition, the magnetoresistance ratio in the ferromagnetic nanotu be device is calculated for a two-band ballistic model, and gives a maximum value of 25%. (C) 2001 Elsevier Science B.V. All rights reserved.