Spin-dependent signatures of induced magnetism in 2D materials

Ruderman–Kittel–Kasuya–Yosida (RKKY) interaction, enables an electrical control of turning the ferromagnetic states ON and OFF in materials doped with dilute magnetic atoms. 2D materials provide a unique platform for RKKY interactions due to their high-gate tunability compared to their 3D counterparts. When the doping is introduced such that the magnetic atoms are between the layers, one can induce magnetism while preserving the interesting properties of the host system. Here, using an atomically-thin boron nitride as the diffusion barrier, we are able to implant dilute Co atoms into van der Waals materials including a 2D semiconductor (black phosphorus) and a 2D superconductor (2H-NbSe2). For the Co-doped black phosphorus, we find that the intrinsic semiconducting properties are well preserved and gate/bias-tunable ferromagnetism up to room temperature is realized. For Co-doped NbSe2, we argue that a ferromagnetic RKKY interaction occurs exclusively below the superconducting transition temperature. Our observations provide direct spin-dependent evidence for induced magnetism in 2D materials.