Multiferroic phase of doped delafossite CuFeO₂ identified using inelastic neutron scattering

We report inelastic neutron scattering measurements that provide a distinct dynamical "fingerprint" for the multiferroic ground state of 3.5% Ga-doped CuFeO₂. The complex ground state is stabilized by the displacement of the oxygen atoms, which contribute to the multiferroic coupling predicted in the "spin-driven" model. By comparing the observed and calculated spectrum of spin excitations, we conclude that the magnetic ground state is a distorted screw-type spin configuration with a distribution of turn angles.