Spin-switch effect from crossed Andreev reflection in superconducting graphene spin valves

We consider the nonlocal quantum transport properties of a graphene superconducting spin valve. It is shown that one may create a spin-switch effect between perfect elastic cotunneling (CT) and perfect crossed Andreev reflection (CAR) for all bias voltages in the low-energy regime by reversing the magnetization direction in one of the ferromagnetic layers. This opportunity arises due to the possibility of tuning the local Fermi level in graphene to values equivalent to a weak magnetic exchange splitting, thus reducing the Fermi surface for minority spins to a single point and rendering graphene to be half metallic. Such an effect is not attainable in a conventional metallic spin valve setup, where the contributions from CT and CAR tend to cancel each other and noise measurements are necessary to distinguish these processes.