The atomic thickness of two-dimensional materials provides a unique opportunity to control their electrical1 and optical2 properties as well as to drive the electronic phase transitions3 by electrostatic doping. The discovery of two-dimensional magnetic materials4,5,6,7,8,9,10 has opened up the prospect of the electrical control of magnetism and the realization of new functional devices11. A recent experiment based on the linear magneto-electric effect has demonstrated control of the magnetic order in bilayer CrI3 by electric fields12. However, this approach is limited to non-centrosymmetric materials11,13,14,15,16 magnetically biased near the antiferromagnet–ferromagnet transition. Here, we demonstrate control of the magnetic properties of both monolayer and bilayer CrI3 by electrostatic doping using CrI3–graphene vertical heterostructures. In monolayer CrI3, doping significantly modifies the saturation magnetization, coercive force and Curie temperature, showing strengthened/weakened magnetic order with hole/electron doping. Remarkably, in bilayer CrI3, the electron doping above ~2.5 × 1013 cm−2 induces a transition from an antiferromagnetic to a ferromagnetic ground state in the absence of a magnetic field. The result reveals a strongly doping-dependent interlayer exchange coupling, which enables robust switching of magnetization in bilayer CrI3 by small gate voltages.
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The research was supported by the ARO Award W911NF-17-1-0605 for sample and device fabrication and the Air Force Office of Scientific Research under grant FA9550-16-1-0249 for optical spectroscopy measurements. We also acknowledge support from the National Science Foundation under Award No. DMR-1420451 (L.L.) and DMR-1410407 (Z.W.), and a David and Lucille Packard Fellowship and a Sloan Fellowship (K.F.M.).