Multiferroic phase stability in non-stoichiometric MnWO4

We investigate the multiferroic phase stability of MnWO4 in response to the non-stoichiometry of Mn and W, given the Mn:W ratio η. It is observed that the non-stoichiometry does not affect remarkably the ferroelectric transition point (the AF3-AF2 transition point) and the AF2-AF1 transition point, but the non-polar AF1 phase is partially replaced by the ferroelectric AF2 phase. The measured electric polarization is slightly enhanced with increasing stoichiometric deviation ∣η − 1∣. The possible underlying mechanism for these effects is discussed.