Edge magnetism in colloidal MoS2 triangular nanoflakes.

The control of localized magnetic domains at the nanoscale holds great promise for next-generation spintronic applications. Colloidal transition metal dichalcogenide nanostructures are experimentally accessible and chemically tunable platforms for spintronics, deserving dedicated research to assess their potential. Here, we investigate from first principles free-standing triangular MoS2 nanoflakes with sulfur-terminated, hydrogen-passivated edges, to probe intrinsic spin behavior at varying side lengths. We find a critical edge length of approximately 1.5 nm separating nonmagnetic nanoflakes from larger ones with a magnetic ground state emerging from several, energetically competing spin configurations. In these systems, the magnetic activity is not uniformly distributed along the edges but localized on specific "magnetic islands" around molybdenum edge atoms. The localization of magnetic moments is robust even in non-equilateral nanoflake geometries, highlighting their intrinsic stability regardless of the (high) symmetry of the hosting structure. Our findings establish that the S-terminated, H-passivated triangular MoS2 nanoflakes are an energetically stable and potentially accessible platform via colloidal synthesis for low-dimensional, next-generation spintronic devices.