Structural and electronic phase transitions in Sr1−xCexMnO3 perovskites

The structures of eight members of the series Sr1−xCexMnO3 with 0.075⩽x⩽0.4 have been established using synchrotron X-ray powder diffraction. These exhibit the sequence of structurescubicPm3¯m⟶x≈0.08tetragonalI4/mcm⟶x≈0.35orthorhombicImmawith increasing Ce content. Unusual peak broadening due to domain wall scattering is observed near the composition-induced first-order cubic–tetragonal transition. The temperature dependence of the structures for three examples x=0.1, 0.2 and 0.35 is described. For the x=0.1 and 0.35 samples evidence for a first-order loss of the orbital ordering associated with a cooperative Jahn–Teller distortion is presented. The onset of the orbitally disordered state is accompanied by a discontinuous reduction in cell volume.

The presence of small amounts of trivalent Mn in the series Sr1−xCexMnO3 has a dramatic effect on the structure, with the structure changing from cubic to tetragonal and finally orthorhombic. The orbital ordering present at room temperature is lost upon heating.Figure optionsDownload as PowerPoint slide