Emergent Transition Metal Dichalcogenide Monolayer Ferromagnetism at Terminated Edges*

The recent discoveries of the strong room-temperature ferromagnetism in epitaxially grown transition metal diselenide XSe₂ (X = V, Mn) monolayers have effectively heated up the field of two-dimensional (2D) van der Waals magnets [1,2]. However, the origin of the ferromagnetism in these nanosystems has remained an open question. In this talk, we demonstrate that chalcogenide (Se) atoms at terminated edges play a dominant role in the XSe₂ monolayer magnetism, regardless of the transition metal being a non-magnetic element (X = W, Ti) or a magnetic element (X = V). The ferromagnetic Se edge is responsible for the observed large magnetic moment, which decreases as the size of XSe₂ islands or the number of XSe₂ layers increases. The role played by the magnetic transition metal (X = V) on the ferromagnetic ordering of monolayer XSe₂ is also elucidated. Density functional theory (DFT) based calculations support the experimental findings. This understanding enables controlled nanoengineering of novel two-dimensional van der Waals magnets for next-generation spintronic devices and storage information applications.

References
[1] M. Bonilla et al., Nature Nanotechnol. 13, 289-203 (2018)
[2] Dante J. O’Hara et al., Nano Lett. 18, 3125–3131 (2018)