Published online by Cambridge University Press: 21 February 2012
We performed magnetoresistance (MR) measurements on bulk carbon nanotube sheets that had been partially aligned by post-fabrication stretching. The magnetic field was applied under different orientations with respect to the direction of the stretch, while the electric current was either parallel or perpendicular to the direction of the stretch. We found that the fielddependence of the MR is composed of two terms, one positive and one negative. The magnitudes of both terms are largest when the field is parallel with the direction of the stretch. If the sheets are treated with nitric acid, the positive term is removed and the MR is smallest when the field is aligned with the magnetic field. We attribute these anisotropic features to magnetoelastic effects induced by the coupling between the magnetic catalyst nanoparticles, the magnetic field, and the network of nanotubes.