Title:Oral: Room temperature multiferroicity in alloys of 2D van der Waals transition metal dichalcogenide materials*

Multiferroics are materials that simultaneously exhibit more than one type of ordering such as magnetic, electric, or elastic. This coexistence of multiple ferroic orders is a scarce property to be found in materials. Historically, this state has been found mainly in 3-dimensional complex oxides, but so far this state has still been elusive for the most widely studied and characterized family of 2-dimensional van der Waals compounds, the transition metal dichalcogenides (TMD). TMDs are composites of the type MX₂, with M a transition-metal atom (Mo, W, etc) and X a chalcogen atom (S, Se or Te). In this talk I will present evidence of multiferroic states in alloys of this family of materials, at room temperature, in bulk single crystals of Te-doped WSe₂. We observe the coexistence of ferromagnetism and ferroelectricity through the presence of magnetization and piezoresponse force microscopy hysteresis loops. Our results prefigure a design strategy of 2D multiferroics based on alloying these compounds by means of chemical  substitutions in the chalcogen site (in this case, W[Te_x Se_1-x]_2-δ, where δ representa vacancies of the chalcogen atoms). These findings open the possibility of widening the use and study of van der Waals-based multifunctional devices for new nanoelectronics and spintronics applications.

[1] Cardenas-Chirivi, G., Vega-Bustos, K., Rojas-Páez, H. et al. Room temperature multiferroicity in a transition metal dichalcogenide. npj 2D Mater Appl 7, 54 (2023). https://doi.org/10.1038/s41699-023-00416-x