Single-Crystal Investigations On The Multiferroic Material Life(Wo4)(2)

The crystal and magnetic structures of multiferroic LiFe(WO4)(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-N1 approximate to 22.2 K and T-N2 approximate to 19 K. First, a spin-density wave develops with moments lying in the ac plane. In its multiferroic phase below T-N2 LiFe(WO4)(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 T. LiFe(WO4)(2) thus exhibits a simple phase diagram with the typical sequence of transitions for a type-II multiferroic material.