Structure and magnetism of Mn, Fe, or Co adatoms on monolayer and bilayer black phosphorus

Black phosphorus (BP) is an emergent layered material and is currently explored for its potential applications in nanoelectronics. Here using density functional calculations, we investigate the structure and magnetism of transition metal (TM) adatoms (Mn, Fe, and Co) on the monolayer and bilayer BP. We find that while the TM adatoms prefer to occupy a valley site of the puckered monolayer BP and have a low-spin magnetic state, they could move to an interlayer interstitial site of the bilayer BP and turn into a high-spin state. In particular, Mn adatom at the valley site of monolayer BP has also a metastable high-spin state, and moreover, a low-spin to high-spin magnetic transition can readily be induced by a strain along the armchair direction. Then Mn adsorbed BP monolayer has a strain-tuning spin switch.