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Ca(2.5)Sr(0.5)GaMn2O8: diamagnetic Ga in control of the structural and electronic properties of a bilayered manganate.

Authors
  • Battle, Peter D
  • Blundell, Stephen J
  • Brooks, Michael L
  • Hervieu, Maryvonne
  • Kapusta, Czeslaw
  • Lancaster, Tom
  • Nair, Santhosh P
  • Oates, Colin J
  • Pratt, Francis L
  • Rosseinsky, Matthew J
  • Ruiz-Bustos, Rocío
  • Sikora, Marcin
  • Steer, Christopher A
Type
Published Article
Journal
Journal of the American Chemical Society
Publication Date
Oct 06, 2004
Volume
126
Issue
39
Pages
12517–12527
Identifiers
PMID: 15453785
Source
Medline
License
Unknown

Abstract

The temperature dependence of the crystal structure and electronic properties of brownmillerite-like Ca(2.5)Sr(0.5)GaMn(2)O(8) has been studied by neutron powder diffraction and muSR spectroscopy. The results show that short-range 2D magnetic order begins to develop within the perovskite-like bilayers of MnO(6) octahedra approximately 50 K above the 3D Néel temperature of approximately 150 K. The bilayers show a structural response to the onset of magnetism throughout this temperature range whereas the GaO(4) layers that separate the bilayers only respond below the 3D ordering temperature. XANES spectroscopy shows that the sample contains Mn(3+) and Mn(4+) cations in a 1:1 ratio, and the behavior in the region of the Néel transition is interpreted as a local charge ordering. Electron diffraction and high-resolution electron microscopy have been used to show that the local microstructure is more complex than the average structure revealed by neutron diffraction, and that microdomains exist in which the GaO(4) tetrahedra show different orientations. It is argued that the bonding requirements of diamagnetic gallium control the electronic behavior within the perovskite-like bilayers.

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