Persistent type-II multiferroicity in nanostructured MnWO4 ceramics

We show that the type-II multiferroic properties of bulk MnWO4 are kept in nanostructured ceramics of 50 nm grain size prepared via spark plasma sintering (SPS). This means that ferroelectric polarization is robust against downsizing, which is at variance with standard ferroelectrics like BaTiO3. We ascribe this stability to the spin-driven nature of the ferroe-lectric correlations in type-II multiferroics while it is resulting from lattice distortion in other cases. This may open the way for persistent type-II multiferroicity with no need for external stabilization like substrate-generated strain.