Edge-state-induced magnetism in two-dimensional hematene

Abstract

Recently, monolayer hematite termed hematene (FeO₂) was exfoliated from its non-van der Waals bulk counterpart (α-Fe₂O₃), and found to prefer ferromagnetic ordering at around room temperature. However, the underlying mechanism of its room temperature ferromagnetism has not been convincingly established. Here, by combining the particle swarm method, first-principles calculations, and Monte Carlo simulations, we reexamine the magnetism of monolayer hematite. It is confirmed that the ground state of infinite two-dimensional hematene possesses the 1T phase similar to MoS₂ and antiferromagnetic exchange coupling between the iron atoms. In contrast to its three-dimensional bulk counterpart, the two-dimensional hematene does not switch into the ferromagnetic phase at room temperature, even in consideration of the Dzyaloshinsky–Moriya interaction. However, it is found that the one-dimensional hematene nanoribbons with width consisting of odd numbers of Fe rows exhibit net magnetic ordering originating from the spin-polarized edge states. The present findings may provide new insights on the magnetism of hematene-based nanostructures.