Anisotropic half-metallicity in zigzag edge SiP₃ nanoribbons

We investigate magnetic and spin-transport properties of the zigzag-edge nanoribbon structures of two-dimensional (2D) SiP₃ system within first-principle calculations. Based on the edge terminations, the nanoribbons can be categorized in three subclasses, two of them with even number of silicon (Si) atoms and one of them with odd number of Si atoms in the one-dimensional unitcell with antiferromagnetic bulk spin-ordering, analogous to their 2D counterpart. All the ribbons exhibit indirect band-gap semiconducting behavior and the gap decreases with increase in width of the ribbons. The nanoribbon with only phosphorus (P) atoms at least along one of the edges show half-metallic behavior over a small bias window, when probed with cross-ribbon external electric field. Especially, the nanoribbon with odd number of Si atoms stabilizes in a ground state with net non-zero magnetization and exhibits half-metallicity only under forward bias. Such anisotropic half-metallicity along with the precise control of the electronic properties in terms of edge and external bias manipulation hold immense potential for spintronic and switching device applications.