  Zigzag nanoribbons of monolayer graphene-like two-dimensional materials host
spontaneous edge magnetism at the zigzag terminations, whose configuration
controls the band gap. In this article, the edge magnetism of zigzag
nanoribbons of bilayer hexagonal crystals are studied. The specific models of
bilayer graphene and bilayer silicene are both studied. As the gated voltage
increases, the total energy level, magnetic structure and band structures of
the ground state and the first quasi-stable excited state are tuned. For
certain region of the gated voltage, the band gaps of spin up and down are
opened and closed, respectively, so that the systems are in the spin-polarized
metallic phase. The spin-polarized conducting edge band of the bilayer
nanoribbons could be applied for gate tunable spintronic devices.
