Phase transformation in hexagonal ErMnO3 under high pressure

Abstract

The pressure-induced phase transition of the hexagonal manganite ErMnO3 has been investigated using the synchrotron x-ray diffraction technique up to 57.6 GPa in a diamond anvil cell. The hexagonal structure exhibits anisotropic compression behavior. The bulk modulus (B0) is 168(3) GPa with B0′ = 4.0 (fixed). At room temperature, ErMnO3 undergoes a hexagonal-to-orthorhombic phase transition at ∼20.2 GPa, but coexists with the orthorhombic phase up to the highest pressure of 57.6 GPa. When laser-heated to 1500-2000 K, the hexagonal ErMnO3 transforms to a denser orthorhombic perovskite structure completely at ∼17 GPa, accompanied by ∼11% volume reduction. The distortion and tilts of the octahedra MnO6 in the orthorhombic structure decrease with increasing pressure. The bulk modulus of the orthorhombic structure is 214(4) GPa with B0′ = 4.0 (fixed), larger than that of the hexagonal structure. The orthorhombic structure ErMnO3 is stable at least up to ∼45 GPa and can be quenched.