▎ 摘　　要

Using the transfer matrix method, the spin transmission coefficient and the spin conductivity are studied theoretically through the monolayer and bilayer graphene periodic ferromagnetic barriers modulated by a homogeneous electric held. The spin conductivity of the systems has an oscillatory behavior with respect to the external electric field which depends on the spin state of electron. In addition, the oscillation amplitude of the spin conductivity and spin polarization increase by increasing the number of barriers, but for a monolayer system with number of barriers greater than thirty, also for a bilayer system with the number of barriers greater than four, the oscillation amplitude does not change significantly. Our probes show that for bilayer system unlike monolayer structure the highest value of spin polarization achieved can be 1 or (-1). So. for designing spintronic devices, bilayer graphene is more efficient. (C) 2013 Elsevier B.V. All rights reserved.