Donnees cristallographiques sur une nouvelle serie de manganites mixtes de terre rare et d'alcalino-terreux

Abstract The synthesis of two new series of oxides: Ba Ln 2 Mn 2 O 7 and Sr Ln 2 Fe 2 O 7 , where Ln is a rare earth, was performed. The experimental conditions are given along with some crystal data. The diffraction patterns show a close resemblance with those of the double-perovskite-block compounds Ba Ln 2 Fe 2 O 7 and Sr Ln 2 Fe 2 O 7 . However, the c a ratio of the tetragonal cell is somewhat larger for the manganese compounds than for the iron compounds, due to a Jahn-Teller distortion of the Mn 3+ O 6 octahedral sites.