Low-temperature structural and magnetic properties of (formula presented) investigated by neutron and synchrotron x-ray diffraction are reported. High-resolution powder diffraction data evidenced two-phase coexistence. One of the phases presents charge-exchange (CE) -type magnetic ordering and (formula presented) structural modulation indicating orbital and charge ordering. The other phase adopts the A-type magnetic structure and orbital ordering with (formula presented) The charge order of the CE phase and the orbital order of the A phase are unusually stable when heating the sample (formula presented) A mechanism, based on the (formula presented) lone pair of (formula presented) ions, is proposed to strongly decrease the mobility of (formula presented) electrons in both phases. This fact, as well as some structural and magnetotransport results, indicates that the A-phase is quite different from previous A phases found in manganites and it cannot be described as a “metallic antiferromagnet.” A possible ordered arrangement of the (formula presented) ions in this phase is examined. © 2001 The American Physical Society.
|Journal||Physical Review B - Condensed Matter and Materials Physics|
|Publication status||Published - 1 Jan 2001|