  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.
