Large magnetoresistance of amorphous carbon films

Abstract

Magnetoresistance (MR) of pure amorphous carbon thin films deposited by pulsed laser deposition at various deposition temperatures was studied. Maximum MR of 46% was observed at 2 K under the magnetic field of 7 T for the sample deposited at temperature of 500 °C. No tendency of MR saturation was observed up to 7 T. The MR decreases rapidly with the increase in measurement temperature and vanishes after 40 K. The transport mechanism of all the samples follow Efros-Shklovskii variable range hopping model. The characteristics temperature decreasing from 2540 K to 1290 K and localization length increasing from 5.3 nm to 10.7 nm with increasing fraction of C(sp2) from 72% to 84%. The lower disorder degree may results in higher MR.