Temperature-mediated switching of magnetoresistance in Co-contacted multiwall carbon nanotubes

Abstract

We present temperature-dependent measurements of the magnetoresistance in ferromagnetically contacted multiwall nanotubes. At low temperature, the resistance increases sharply near zero-field due to misalignment of the contact magnetizations. As temperature increases, the resistance peak transforms into a resistance dip, with a peak-to-valley ratio of similar magnitude, but opposite sign. The resistance switch has a distinct temperature dependence compared with the background magnetoresistance, suggesting that the two have different origins. We propose that a ferromagnetic transition near the contact interfaces reverses the polarity of the injected spin, and changes the sign of the resistance switch.