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