Enabling room-temperature ferromagnetism in few-layered MoS2 films via strain engineering

Strain engineering presents a promising pathway for modulating the physical properties of two-dimensional (2D) transition metal dichalcogenides materials. In this study, we investigate the strain-induced magnetic behavior of diamagnetic MoS2 films prepared by the DC magnetron sputtering technique. By applying +1% tensile strain to few-layered MoS2 films (∼3.5 nm), we observe the emergence of room-temperature ferromagnetism with a magnetization saturation of about ∼130 emu/cm3, in stark contrast to bulk films (∼40 nm), which remain diamagnetic under similar conditions. Raman spectroscopy reveals a pronounced reduction in the intensity and the splitting of the E′ mode in 1% strained few-layered films, indicating a possible bond elongation and symmetry breaking under tensile stress. Additionally, x-ray absorption spectroscopy at the Mo M3 edge further confirms a strain-induced electronic structure modification in few-layered films, with no corresponding shift observed in bulk counterparts. Moreover, the strain-induced magnetic and structural changes are largely reversible upon strain release. We attribute the origin of ferromagnetism in few-layered films to the combined influence of tensile strain and defect-assisted bond weakening, which facilitates crystal field transitions within the Mo 4d orbitals. These findings demonstrate that strain engineering can effectively induce and modulate magnetism in 2D materials, providing opportunities for developing strain-controlled spintronic applications.