Magnetic Excitation Spectrum of Rouaite, Cu₂(NO₃)(OD)₃

The mineral rouaite, Cu₂(NO₃)(OD)₃ in synthetic form, consists of triangular-lattice planes of Cu2+, compressed along the crystallographic b axis to form chains. Below 4.8 K, these chains alternate ferro- and antiferromagnetic, with consecutive ferromagnetic chains having opposite spin orientation. This is essentially the same magnetic sublattice and magnetic ground state as in Cu(OD)₃Br (botallackite), the only material in which spinon-magnon mixing has been reported to date. We propose to look for spinon-magnon mixing in rouaite, starting with time-of-flight spectroscopy. This will also reveal the magnon spectrum, allowing us to model the interaction parameters underlying the magnetic order. Above 4.8 K, rouaite enters an incommensurate phase, the excitation spectrum of which would also provide crucial information.