Magnetic single-layer nanoribbons of manganese oxide: edge- and width-dependent electronic properties

Abstract

In the present work, the structural, magnetic, and electronic properties of the two- and one-dimensional honeycomb structures of recently synthesized MnO [Zhang et al., Hexagonal metal oxide monolayers derived from the metal-gas interface, Nat. Mater., 2021, 20, 1073–1078] are investigated by using first-principles calculations. Our calculations show that the single-layer 2D MnO crystal has a degenerate antiferromagnetic (AFM) ground state and a relatively less favorable ferromagnetic (FM) state. In addition, the magnetic anisotropy calculations unveil that the easy-axis direction for magnetism originating from unpaired electron states in manganese atoms is normal to the crystal plane. Electronically, while the FM MnO is a direct semiconductor with a narrow bandgap, AFM phases display large indirect bandgap semiconducting behavior. Moreover, the calculations on nanoribbons of MnO reveal that zigzag-edged ribbons display metallic behaviors, whereas armchair-edged nanoribbons are semiconductors. Magnetically, for both zigzag- or armchair-edged nanoribbons, the AFM order perpendicular to the nanoribbon growth direction is found to be favorable over the other AFM and FM orders. Moreover, depending on the edge symmetry and ribbon width, forbidden bandgap values of nanoribbons display distinct family behaviors.