Multiferroicity in alloys of 2D transition-metal dichalcogenides

Abstract

Multiferroics are materials that simultaneously exhibit more than one type of ordering such as magnetic, electric, or elastic. Multiferroicity enables the development of new devices for information processing and storage due to the possibility of controlling one type of polarization using a field different from its conjugate field (e.g., magnetic polarization through an electric field). The existence of multiferroic properties in two-dimensional (2D) materials promises advantages in the development of multifunctional devices at smaller scales. These materials, which are intrinsically 2D, are formed by stacking atomically thin layers of crystalline structures with Van der Walls interatomic forces between them, which permits nano-structuration to obtain individual layers from the bulk material. One of the most studied 2D materials families is the Transition-metal dichalcogenides (TMD), composites of the type MX2, with M a transition-metal atom (Mo, W, etc) and X a chalcogen atom (S, Se or Te). The recent discovery of room-temperature multiferroicity in alloys of TMDs opens new possibilities in multifuctional devices at the nanoscale. In this thesis work we propose to study the emergence of multiferroic states in alloys of TMDs and to explore the physical and chemical conditions favorable for their appearance. We want to explore the possibilities opened by substitutions of chalcogen atoms, M(X_xY_{1¿x})_2, or transition metal atoms, (M_xN_{1¿x})X_2, into the structure of the original material MX_2. In particular, we want to deepen our understanding of electric and magnetic properties of W(Se_{1¿x}Te_x)_{2¿¿} from bulk to the nanoscale limit and the dependence of these properties with different tuning parameters.