  Electrostatic gating provides a way to obtain key functionalities in modern
electronic devices and to qualitatively alter materials properties. While
electrostatic description of such gating gives guidance for related doping
effects, inherent quantum properties of gating provide opportunities for
intriguing modification of materials and unexplored devices. Using
first-principles calculations for Co/bilayer graphene, Co/BN, and Co/benzene,
as well as a simple physical model, we show that magnetic heterostructures with
two-dimensional layered materials can manifest tunable magnetic proximity
effects. van der Waals bonding is identified as a requirement for large
electronic structure changes by gating. In particular, the magnitude and sign
of spin polarization in physisorbed graphene can be controlled by gating, which
is important for spintronic devices.
