Effect of substrate temperature on the spin transport property in C60-based spin valve devices

We report the effect of the substrate temperature on the magnetoresistance (MR) of the 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 all types of devices showed a monotonic increase in MR ratio with the substrate temperature. And more interesting, an especially large MR (28.5%) were obtained in the device fabricated at higher substrate temperature, while for the other types of devices, the MR magnitudes were just about a few percent. Based on the I-V measurements, as well as SEM and AFM characteristics, we have obtained 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.