Structural and magnetic properties of the colossal magnetoresistance perovskite

Abstract

A single phase sample of (Formula presented) with uniform cation distribution and complete oxygen stoichiometry was synthesized by freeze-drying technique and studied by a variety of methods. The sample is ferromagnetic below (Formula presented) with (Formula presented) at 10 K. Precise examination of the crystal structure by a combination of electron diffraction, high-resolution electron microscopy, and neutron powder diffraction revealed a monoclinic distortion of the (Formula presented)type structure (Formula presented) with nonequivalent (Formula presented) layers alternating along the a axis. The crystal structure is characterized by a specific pattern of Mn-O distances implying an unconventional orbital ordering type. A possible relation to charge ordering is described within the bond valence sum framework. © 2000 The American Physical Society.