We report the fabrication of the La2/3Sr1/3MnO3 (LSMO)/graphene/Co sandwich structures employing single-layer graphene as the interlayer. Appreciable negative spin valve signals were observed from room temperature to 5 K. We find that the devices demonstrate nonlinear current–voltage (I–V) characteristics around room temperature, indicating that the tunneling effect is dominated rather than the Ohmic property. However, I–V curves exhibit evident linear behavior at low temperatures, which reveal the Ohmic characteristic. The vertical graphene spin valves using LSMO electrode have potential application in memory storage and logic operation.Keywords: chemical vapor deposition; graphene; magnetoresistance; spin-dependent transport; spintronics;

We report the effect of the substrate temperature on the magnetoresistance (MR) of C60-based spin-valve (SV) devices with the sandwich configuration of La0.67Sr0.33MnO3 (LSMO)/C60/cobalt (Co). The C60 interlayer deposited at different substrate temperatures resulted in four types of devices. We observed that all types of devices showed a monotonic increase in their MR ratio with the substrate temperature. Interestingly, an especially large MR (|−28.5%|) was obtained in the device fabricated at a higher substrate temperature, whereas for the other types of devices, the MR magnitudes were about a few percent. On the basis of the I–V measurements as well as SEM and AFM characteristics, we have found that the higher substrate temperature can cause many pits and hollows in the organic film, and these pits will increase the tunneling probability of spin-polarized carriers from one ferromagnetic electrode to the other.Keywords: magnetoresistance effect; organic spin valves; organic spintronics; substrate temperature;