Magnetic Properties of Transition-Metal Adsorbed ot-Phosphorus Monolayer: A First-principles and Monte Carlo Study

Using the first-principles and Monte Carlo methods, here we systematically study magnetic properties of monolayer octagonal-tetragonal phosphorus with 3d transition-metal (TM) adatoms. Different from the puckered hexagonal black phosphorus monolayer (phosphorene or $\alpha$-P), the octagonal-tetragonal phase of 2D phosphorus (named as ot-P or $\epsilon$-P in this article) is buckled with octagon-tetragon structure. Our calculations show that all TMs, except the closed-shell Zn atom, are able to strongly bind onto monolayer $ot$-P with significant binding energies. Local magnetic moments (up to 6 $\mu$B) on adatoms of Sc, Ti, V, Cr, Mn, Fe and Co originate from the exchange and crystal-field splitting of TM 3d orbitals. The magnetic coupling between localized magnetic states of adatoms is dependent on adatomic distances and directions. Lastly, the uniformly magnetic order is investigated to screening two-dimensional dilute ferromagnets with high Curie temperature for applications of spintronics. It is found that ot-P with V atoms homogeneously adsorbed at the centre of octagons with a concentration of 5% has the most stable ferromagnetic ground state. Its Curie temperature is estimated to be 173 K using the Monte Carlo method.