High-pressure phase transitions in BiFeO3: hydrostatic vs.   non-hydrostatic conditions
  We report high-pressure x-ray diffraction experiments on BiFeO3 (BFO) single crystals in diamond-anvil cells up to 14 GPa. Two data sets are compared, one in hydrostatic conditions, with helium used as pressure-transmitting medium, and the other in non-hydrostatic conditions, with silicon oil as pressure-transmitting medium. It is shown that the crystal undergoes different phase transitions in the two cases, highlighting the high sensitivity of BFO to non-hydrostatic stress. Consequences for the interpretation of high-pressure structural studies are discussed. 
Mael Guennou, Pierre Bouvier, Rapha\"el Haumont, Gaston Garbarino and   Jens Kreisel
cond-mat.mtrl-sci