Abstract
Results of a powder neutron diffraction study of the high-temperature monoclinic to a low-temperature monoclinic phase transition in discovered recently by Ragini et al. are presented for The powder neutron diffraction pattern of the phase contains superlattice reflections which have all odd hkl Miller indices with respect to a doubled elementary perovskite cell, characteristic of antiphase tilting of oxygen octahedŕa. In analogy to other perovskite systems, the appearance of these superlattice reflections is attributed to an instability at the R point of the cubic Brillouin zone. We show that the most plausible space group of the phase is Pc. Results of Rietveld refinement for this space group are presented to show that the oxygen octahedra indeed undergo antiphase rotations about [001] direction.
- Received 29 August 2001
DOI:https://doi.org/10.1103/PhysRevB.65.060102
©2002 American Physical Society