Phase precipitation in the Bi_1−xCa_xMnO₃ compounds (x = 0.4–0.6)

¹ Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences Beijing 100190, PRC
² School of Materials Science and Engineering, Guilin University of Electronic Technology Guilin 541004, Guangxi, PRC
³ NIST Center for Neutron Research, National Institute of Standards and Technology Gaithersburg, MD 20899-8562, USA

^(a) ghrao@iphy.ac.cn
rgh@guet.edu.cn (corresponding author)

Received: 10 December 2012
Accepted: 25 February 2013

Abstract

Charge ordering (CO) in Bi_1−xCa_xMnO₃ (x = 0.4–0.6) has been investigated by temperature-dependent high-resolution neutron powder diffraction (NPD), X-ray powder diffraction (XRD) and physical property measurements. Anomalies in magnetization, resistivity and lattice parameters have been observed around the CO transition temperature (T_CO) reported in the literature. However, a scrutiny of the NPD and XRD data at different temperatures and the electron diffraction experiments at 300 K give no evidence of a long-range CO below the reported T_CO. Instead, NPD and XRD reveal a coexistence of two orthorhombic phases in the samples below the reported T_CO. All the experiments suggest that one of the coexisting phases is originated from a precipitation or an incomplete structural transition of the other phase and the reported T_CO corresponds to the precipitation reaction or structural transition temperature, rather than a CO transition temperature.