▎ 摘　　要

Rhombohedral stacked multilayer graphene displays the occurrence of a magnetic surface state at low temperatures. Recent angular resolved photoemission experiments demonstrate the robustness of the magnetic state in long sequences of ABC graphene. Here, by using first-principles calculations, we show that field-effect doping of these graphene multilayers induces a nonrigid electronic structure deformation and stabilizes a perfect half-metallic behavior with nearly 100% of spin current polarization and sizable conductivity already at dopings attainable in conventional field-effect transistors with solid state dielectrics. At high doping, magnetism disappears and a flat electronic band prone to correlated, charge density wave, or superconducting instabilities occurs at the Fermi level. Our work demonstrates the realizability of a new kind of spintronic devices where the transition between the low resistance and the high resistance state is driven only by electric fields.