Due to their application potential for new types of memory devices, the research on multiferroic materials has attracted strong interest during the last decades. A prominent mechanism that drives multiferroic behavior is given by the inverse Dzyaloshinskii-Moriya interaction, which yields the shift of a non-magnetic ligand ion due to a non-collinear magnetic structure. It was shown on a powdered sample of LiFe(WO$_4$)$_2$ that the onset of a spiral spin structure is accompanied by an evolving ferroelectric polarization, whose direction is consistent with the inverse DMI . Here, we report on our single crystal investigations on LiFe(WO$_4$)$_2$, for which we utilized neutron scattering experiments on HEIDI and on KOMPASS . It was possible to determine the magnetic structure of both incommensurate phases at low temperature, which follow the typical sequence of magnetic phases for a type-II multiferroic material. First, in the intermediate phase a spin-density wave forms and subsequently in the multiferroic phase, a chiral spin structure evolves. Furthermore, longitudinal neutron polarization analysis on the cold three-axes spectrometer KOMPASS revealed a partially unbalanced multiferroic domain distribution that develops in the multiferroic phase and even in absence of external fields.
 Liu et al., Phys. Rev. B 95, 195134 (2017)  Biesenkamp et al., Phys. Rev. B 103, 134412 (2021)