Ferromagnetism in two-dimensional metal dibromides induced by hole-doping.

Using spin-polarized first-principles calculations based on density functional theory, we study the stability, electronic properties and magnetic behavior induced by hole-doping of two-dimensional (2D) PbBr and HgBr. Although inherently nonmagnetic, these materials can exhibit stable ferromagnetic order when hole-doped at densities above a few 10 cm. We also examined the impact of intrinsic and extrinsic defects on inducing hole-doping and subsequent ferromagnetism. Our findings suggest that p-type doping can be achieved by Pb and Hg vacancies and Br antisites, but the latter behaves as deep acceptors. Among the possible dopants we considered, Li substituting Pb or Hg, and S replacing Br in 2D HgBr, can produce shallow acceptor states near the valence band edges and potentially result in a stable ferromagnetic order in these 2D dibromides.