Bipolar magnetic semiconductors and half-metals in transition metals doped SnSe2 zigzag nanoribbons

The magnetic and electronic properties of transition metals (TM) (TM = Sc, Ti, V, Cr, Mn, Fe, Co, and Ni) doped SnSe2 zigzag nanoribbons (ZNRs) are investigated by employing density functional theory. When an Sn atom on edge of ZNR is substituted by Sc atom, the ZNR behaves as bipolar magnetic semiconductors with 100% spin polarization of valence band and conduction band carriers, where the spin-polarization direction can easily be switched by an external electric field. The Cr-doped ZNR is a spin-gapless semiconductor in which the valence band and conduction band in the spin-up channel touch each other at Fermi energy. The others either are usual magnetic semiconductors or nonmagnetic semiconductors. When two Sn atoms on the edge are substituted by Cr atoms, it is observed that the SnSe2 nanoribbon exhibits half-metallic behavior. Either one Cr dopant or two Cr dopants on edge, the nanoribbons have stable 100% spin polarization of conduction carriers at a wide energy range. These findings demonstrate that the Sc-, Cr-, and 2Cr-doped SnSe2 zigzag nanoribbons are excellent candidates for spintronics.