Structural polymorphism in multiferroic BiMnO3 at high pressures and temperatures

Abstract Structural phase transitions in BiMnO 3 were studied by means of energy-dispersive X-ray diffraction in the pressure 0–4 GPa and temperature 300–900 K ranges, and also by means of angle-dispersive X-ray diffraction and Raman spectroscopy at high pressures up to 50 GPa and ambient temperature. The P – T phase diagram of BiMnO 3 was constructed. A suppression of the transition temperatures between monoclinic C2/c and orthorhombic Pnma phases was observed under pressure. The temperature and pressure dependencies of lattice parameters were obtained. A new orthorhombic Imma phase was observed at P  > 20 GPa. The lattice dynamics calculations were performed for the analysis of the Raman spectra of BiMnO 3 .