The crystal and magnetic structures of multiferroic $\mathrm{LiFe}{\left({\mathrm{WO}}_4\right)}_2$ were investigated by temperature and magnetic-field-dependent specific heat, susceptibility, and neutron diffraction experiments on single crystals. Considering only the two nearest-neighbor magnetic interactions, the system forms a $J_1, J_2$ magnetic chain, but more extended interactions are sizable. Two different magnetic phases exhibiting long-range incommensurate order evolve at $T_{\text{N}1}\approx 22.2\mathrm{K}$ and $T_{\text{N}2}\approx 19\mathrm{K}$. First, a spin-density wave develops with moments lying in the $ac$ plane. In its multiferroic phase below $T_{\text{N}2}, \mathrm{LiFe}{\left({\mathrm{WO}}_4\right)}_2$ exhibits a spiral arrangement with an additional spin component along $b$. Therefore, the inverse Dzyaloshinskii-Moriya mechanism fully explains the multiferroic behavior in this material. A partially unbalanced multiferroic domain distribution was observed even in the absence of an applied electric field. For both phases only a slight temperature dependence of the incommensurability was observed, and there is no commensurate phase emerging at low temperature or at finite magnetic fields up to $6\mathrm{T}$. $\mathrm{LiFe}{\left({\mathrm{WO}}_4\right)}_2$ thus exhibits a simple phase diagram with the typical sequence of transitions for a type-II multiferroic material.

• Received 23 November 2020
• Accepted 25 March 2021

DOI:https://doi.org/10.1103/PhysRevB.103.134412