Magnetic properties of transition metal Mn, Fe and Co dimers on monolayer phosphorene.

We studied the geometries, electronic structure and magnetic properties of substitutional doping and adsorption of transition metal (Mn, Fe and Co) dimers on phosphorene monolayer in the framework of the generalized gradient approximation (GGA) and GGA + U. Electronic band structures and magnetic properties were dependent on the doping type and dopant materials. For Mn and Fe substitutional and adsorption dimers, we obtained semiconducting band structures with spin polarization. However, we found a half-metallic feature in Co substitutional dimer while the Co adsorption dimer showed a semiconducting behavior without any spin polarization. With GGA + U, all the systems showed spin polarized semiconducting band structures except Co adsorption dimer which remained unaffected. The hybridization between transition metal (TM) and phosphorene sheet contributed to suppressing the magnetic moment of TM dimers. For instance, the total magnetic moments of -2.0, 4.24 and 1.28 μ B/cell for Mn, Fe and Co substitutional dimers were obtained while the Mn and Fe adsorption dimers showed magnetic moments of -1.69 and 0.46 μ B/cell. These magnetic moments were enhanced with GGA + U. The same magnetic ground states were obtained both from GGA and GGA + U approaches except for the Mn dimers. We observed that the Mn and Fe substitutional dimers showed an out-of-plane magnetization while an in-plane magnetization was observed in Co substitutional dimer. The Mn adsorption dimer still displayed a perpendicular magnetization whereas the Fe adsorption dimer had an in-plane magnetization. We found that the both GGA and GGA + U showed the same magnetization direction in all the systems.