Spin Transport in Multi Wall Carbon Nanotubes with Co Electrodes

The magnetic field dependent transport behaviour of Co contacted multi-wall nanotubes is investigated. A sample with three Co electrodes has been measured by two-channel method with an in-plane magnetic field. When the in-plane magnetic field is perpendicular to the tube, high positive magnetoresistance up to 30% is btained at low temperature from 3K to 25K and with field parallel to the tube, negative magnetoresistance up to 15% is observed only from the high resistance junction. The detailed positive and negative magnetoresistance behaviour also changes with temperature.