▎ 摘　　要

The degradation mechanisms of multilayer graphene spin valves are investigated. The spin injection signals in graphene spin valves have been reported to be linearly dependent on the drain bias voltage, which indicates that the spin polarizations of injected spins in graphene are robust with respect to bias voltage. We report that the disappearance of this robustness can be due to two different degradation mechanisms of the spin valves. Our findings indicate that the disappearance of robustness is due to degradation rather than any intrinsic characteristic of graphene. Thus, the robustness can be greatly enhanced if degradation can be prevented. (C) 2009 The Japan Society of Applied Physics DOI: 10.1143/APEX.2.123004