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We investigate theoretically the behavior of electron spin states near graphene edges at low temperature in the presence of an external electric field. The graphene Hamiltonian is solved directly in the low energy regime including the Rashba spin-orbit interaction. Spin propagation in graphene and spin reflection at the edge are explored by calculating the probability of spin flips between the final and initial states. The spin scattering at the edge is affected by the initial location and the propagating direction of the electron with respect to the edge. Results for an example device structure including the effects of the non-uniform electrostatic field and potential near the graphene edge are presented. [ABSTRACT FROM AUTHOR]

Graphene is an ideal material for spintronic devices due to its low spin-orbit coupling and high mobility. One of the most important potential applications of graphene spintronics is for use in neuromorphic computing systems, where the tunable spin resistance of graphene can be used to apply analog weighting factors. A key capability needed to achieve spin-based neuromorphic computing systems is to achieve distinct regions of control, where injected and detected spin currents can be tuned independently. Here, we demonstrate the ability to achieve such independent control using a graphene spin valve geometry where the injector and detector regions are modulated by two separate bottom gate electrodes. The spin transport parameters and their dependence on each gate voltage are extracted from Hanle precession measurements. From this analysis, local spin transport parameters and their dependence on the local gate voltage are found, which provide a basis for a spatially-resolved spin resistance network that simulates the device. The data and model are used to calculate the spin currents flowing into, through, and out of the graphene channel. We show that the spin current flowing through the graphene channel can be modulated by 30% using one gate and that the spin current absorbed by the detector can be modulated by 50% using the other gate. This result demonstrates that spin currents can be controlled by locally tuning the spin resistance of graphene. The integration of chemical vapor deposition (CVD) grown graphene with local gates allows for the implementation of large-scale integrated spin-based circuits. [ABSTRACT FROM AUTHOR]