Magnetic 3d Transition Metal Atomic Chains Modulated by the Intrinsic Valley Structure in MX Monolayer

A systematic study of 3d transition metal (TM) atomic chains adsorbed on monolayer MX (M = Si/Ge, X = P/As) by using first-principle calculations is presented. The results demonstrate that all 3d TMs, except for the fullfilled shell Zn atom, will spontaneously adsorb on the top of the bridge site over the (MM)_x bond in the intrinsic valleys of MX monolayer forming atomic chains with sizable adsorption energies. For TMs from Sc to Co, the TM–MX systems exhibit nonzero magnetic moments. The ferromagnetic characters of atomic chains are mainly influenced by the interactions between TMs and X atoms and also M atoms in the valleys of monolayer MX. Furthermore, the magnetism of TM–MX systems with TMs varying from Sc to Zn are maintained under moderate external uniaxial or biaxial strains. The work proposes a new possible route exploiting the intrinsic crystal structure of MX to synthesize ferromagnetic atomic chains. The sizable adsorption energy, high spin polarization, and good flexibility promise TM–MX systems rich potential applications in spintronics and magnetoelectric devices.