  Doping of the graphene lattice with transition metal atoms resulting in high
magnetic anisotropy energy (MAE) is an important goal of materials research
owing to its potential application in spintronics. In this article, by using
spin-polarized density functional theory including spin-orbit coupling, we
examined magnetic properties of graphene with vacancy defects, both bare and
nitrogen-decorated, and doped by Cr, Mn and Fe transition metal single atom
(TM-SA) and two different TM atoms simultaneously. [...] The computational
findings are supplemented by an atomic-resolution characterization of an
incidental Mn impurity bonded to four carbon atoms, whose localized spin
matches expectations as measured using core-level electron energy-loss
spectroscopy. Conducting TM-doped graphene with robust magnetic features offers
prospects for the design of graphene-based spintronic devices.
