A variable temperature synchrotron X-ray diffraction study of the ferroelastic double perovskite Ba2GdMoO6

Abstract

A study of the magnetic and structural properties of the double perovskite Ba₂GdMoO₆ has been performed. The crystal structure distorts from the ideal cubic (Fmm) structure to the tetragonal space group I4/m at 220 K, before undergoing a second distortion to a triclinic system (I) at 80 K. The phase transition to triclinic symmetry is also evident in magnetic susceptibility measurements. The variable temperature synchrotron powder X-ray diffraction results reveal that Ba₂GdMoO₆ is ferroelastic, with the onset of ferroelastic domain formation occurring at the cubic–tetragonal phase transition. A number of Rietveld refinement techniques for modelling diffuse scattering from ferroelastic domain boundaries have been explored.