Electric and thermal spin transfer torques across ferromagnetic/normal/ferromagnetic graphene junctions

We investigate the spin transfer torque (STT) driven by electric bias voltages across and temperature gradients through ferromagnetic/normal/ferromagnetic graphene junctions. Due to the unique band structure of the ferromagnetic graphene, there exists two transport regimes: the electron to electron (I) and hole to electron (II) transport. The electric STTs originated from the two regimes have opposite sign and can be reduced by the competition between the two transport processes. On the contrary, the thermal STTs originated from the transport regimes I and II have the same sign and are enhanced when the two regimes coexist. Remarkably, the thermal STT is comparable with the electric STT. Furthermore, the electric and thermal counterpart can be manipulated by the Fermi level. The controllable STT reported here makes the ferromagnetic graphene junction ideal for future spintronics applications. (paper)