Asymmetric magnetoconductance and magneto-Coulomb effect in a carbon nanotube single electron transistor.

We report single step-like asymmetric magnetoconductance from a double-walled carbon nanotube single electron transistor contacted by ferromagnetic cobalt electrodes. The device conductance changed significantly when the direction of the applied magnetic field was reversed, but did not show the spin-valve-type double extrema feature near the coercive field of the electrodes. The magnetoconductance also showed quasi-periodic sign-reversing oscillations with respect to the applied bias. The bias-dependent oscillation of the magnetoconductance was compared with the quantum dot stability diagram for the device. As a result, it was confirmed that the asymmetric magnetoconductance was caused by the magneto-Coulomb effect.