Room-temperature vibrational properties of multiferroic MnWO4 under   quasi-hydrostatic compression up to 39 GPa
  The multiferroic manganese tungstate (MnWO4) has been studied by high-pressure Raman spectroscopy at room temperature under quasi-hydrostatic conditions up to 39.3 GPa. The low-pressure wolframite phase undergoes a phase transition at 25.7 GPa, a pressure around 8 GPa higher than that found in previous works which used less hydrostatic pressure-transmitting media. The pressure dependence of the Raman active modes of both the low- and high-pressure phases are reported and discussed comparing with the results available in the literature for MnWO4 and related wolframites. A gradual pressure-induced phase transition from the low- to the high- pressure phase is suggested on the basis of the linear intensity decrease of the Raman mode with the lowest frequency up to the end of the phase transition. 
J. Ruiz-Fuertes, D. Errandonea, O. Gomis, A. Friedrich, and F. J.   Manjon
cond-mat.mtrl-sci