Chirality selection by magnetoelectric coupling in frustrated hexagonal antiferromagnets

Symmetry arguments are used to demonstrate that an electric field applied in the basal plane of a stacked triangular antiferromagnet breaks chiral degeneracy associated with the frustration-induced 120^∘{} spin structure. This is achieved through magnetoelectric coupling which introduces a Dzyaloshinsky-Moryia type of interaction. The electric-field--temperature phase diagram is investigated through the analysis of a Landau-type free energy and the connection with recent renormalization-group calculations is made. Possible applications to CsMnBr₃ and related materials are discussed.