Macroscopic phase separation in layered manganite induced by a surface effect

We report on the origin of the perovskite phase intergrown in the layered m anganite, Sr1.6La1.4Mn2O7. X-ray powder diffraction, magnetization, and tra nsport measurements on the Sr1.6La1.4Mn2O7 materials prepared under various conditions show that the perovskite phase is grown predominantly on the su rface region in contact with either air or the substrate. With intermediate grinding and sintering the perovskite impurity increases rather than trans forms to Sr1.6La1.4Mn2O7. The results provide important information for the understanding of the layered manganite system in which the compositional f luctuation occurs naturally due to the intergrown perovskite phase. (C) 200 1 Published by Elsevier Science Ltd.